Daniele Fabrizio Bignami · Renzo Rosso Umberto Sanfilippo

Daniele Fabrizio Bignami · Renzo Rosso Umberto San lippo Flood Proo ng in Urban Areas Flood Prooﬁng in Urban Areas Daniele Fabrizio Bignami • Renzo Rosso • Umberto Sanﬁlippo

Flood Prooﬁng in Urban Areas Daniele Fabrizio Bignami Renzo Rosso Fondazione Politecnico di Milano DICA Milan, Italy Politecnico di Milano Milan, Italy

Umberto Sanﬁlippo DICA Politecnico di Milano Milan, Italy

ISBN 978-3-030-05933-0 ISBN 978-3-030-05934-7 (eBook) https://doi.org/10.1007/978-3-030-05934-7

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This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland Foreword

Flood proofing (often indicated as Floodproofing) is a term indicating a large number of different measures, tools, and procedures, which can be implemented to reduce the flood risk by decreasing the exposure and/or the vulnerability of people, buildings, infrastructures, and goods during a flood event. Although the origin of flood proofing is historically far antecedent, and much literature was already available at that time, in 2012 a precise definition of this concept has been reported in the Issue No. 15 of the Integrated Flood Management Tools Series of the Associated Programme on Flood Management (APFM), which is a joint initiative of the World Meteorological Organization (WMO) and the Global Water Partnership (GWP). According to that milestone document, flood proofing includes both structural and non-structural measures against flood damage before or during flooding. Essen- tially, flood proofing covers two purposes of flood management: flood resistance and flood resilience; flood resistance keeps out flood water to prevent damages, while the flood resilience minimizes the impacts of flood water once a flood occurs. In general, as it is getting difficult to bear the increasing costs of investing in structural flood protection, governments need to rely more on non-structural measures of regulations and incentive mechanisms in addition to conventional large- scale flood prevention measures. Furthermore, residents and communities need to make more in terms of individual efforts on flood proofing to protect their properties. Definitively, flood proofing approaches are a valuable and modern way to help to meet the main target of protecting the territory against flooding, by means of smaller widespread diffused interventions which are cost-effective and integrate large-scale flood control infrastructures. So, a lot of problems of civil protection can be handled by the right solutions, with a quite low socioeconomic impact in almost any urban context that flood proofing offers to everybody responsible for planning flood management, designing flood defense systems, and operating flood control systems in the public and private sectors.

v vi Foreword

In this framework, I am glad to say that the present book is a remarkable summary of the state of the art of flood proofing principles, methodologies, tools, norms, and tests, including a large number of tables, schemes and pictures. Moreover, the book proposes a rational redefinition of flood proofing classification, suggesting that operative criteria about the most suitable kind of flood proofing intervention could be adopted in practice, case by case, at point or areal scale. An interesting review of the physics of stability and instability of both human beings and buildings under flood conditions completes the book contents. I do hope that the readers of this book will appreciate the efforts carried out by my estimated colleagues Renzo Rosso, Daniele F. Bignami, and Umberto Sanfilippo to provide such a useful and clear description of the different flood proofing aspects including some innovative issues too. Bologna (Italy), May 3, 2019

Department of Civil, Chemical, Alberto Montanari Environmental and Material Engineering University of Bologna Bologna, Italy European Geosciences Union (EGU) Munich, Germany Preface

The disasters caused by inundations all over the world may have quite different impacts on territories and people. It depends on flood magnitude, exposure and resilience of the threatened land, and the effectiveness of the measures (permanent and/or temporary) adopted to protect human settlements. Traditional approaches to cope with floods deal with creating or reinforcing risk reduction measures. These can be structural and/or non-structural. The first ones (raising levees, enhancing hydraulic conveyance, creating overflows and diversions, either building or improving dams and storage facilities, forest and agricultural adjustments) are essentially permanent (sometimes including real-time control features for overflows, diversions, impounding facilities). Non-structural measures include source control, including watershed and landscape structure management; laws and regulations, including zoning; economic instruments such as insurance plans; flood forecast and warning systems; and a comprehensive system of flood risk assessment, awareness raising, flood-related databases, and safety evacuation procedures. Like structural measures, the non-structural ones also require continuous care to provide the best performance in case of disasters. One can integrate this approach with temporary measures that are often capable of substantially enhancing the performance of the permanent defense measures. In the last few decades, flood proofing showed to provide quite satisfactory results in terms of damage reduction. After the United States pioneered this approach, many countries have progressively introduced flood proofing among flood risk reduction measures and, most of all, adapted it to specific urban and rural landscape, with features changing from case to case. Flood proofing usually refers to a large number of interventions, such as building repositioning or lifting, dry or wet flood proofing of the buildings, self-mobile barriers, emergency dikes and/or berms, and even the old-fashioned sand sack walls. All these measures or devices aim at reducing or at least controlling flood impact at the local or municipal scale. This requires taking care of people’s safety, building damage, and infrastructural protection during an inundation.

vii viii Preface

This book reviews literature on flood proofing concepts, techniques, and devices. This includes physics of stability and instability of both human beings and buildings under flood attack, criteria and models to assess flood strain, and safety margins for flood proofing devices and facilities. An updated and enhanced classification of flood proofing methods and devices is presented here to better identify the appropriate solutions to specific risk scenarios and to address the most effective ones from both technical and economical point of view. The focus on temporary flood proofing techniques descends from their capability to meet performance efficiency under a satisfactory cost to benefit framework. Most of examples shown are real case studies, without mentioning manufacturers or commercial products. The book finally reports a resume of norms, guidelines, and laboratory test recommendations for flood proofing devices currently in use in different countries, given that diversity of landscape and social patterns requires a multifaceted and flexible approach. The purpose of this book is to encourage authorities, stakeholders, and end users to develop appropriate flood proofing solutions to mitigate flood risk under a pragmatic approach.

Milan, Italy Renzo Rosso May 26, 2019 Daniele Fabrizio Bignami Umberto Sanﬁlippo Acknowledgments

The authors wish to thank Fondazione CARIPLO (CARIPLO Foundation) for its support of the Project “FLORIMAP—smart FLOod RIsk MAnagement Policies,” as the results achieved by this research inspired useful leads for some of the issues presented in this book. In addition, the authors most gratefully acknowledge the former support by Italian CNR-GNDCI, which fostered pioneering research in the area of ﬂood mitigation. And, last but not least, we wish to thank our dear families; they are always by our side, giving us reasons to cheer and to go ahead.

ix Contents

1 Introduction ...... 1 References ...... 8 2 Flood Impact on Buildings ...... 11 2.1 Introduction ...... 11 2.2 Evaluation Criteria ...... 11 2.2.1 Analysis of Stormwater Effects ...... 11 2.2.2 Buoyancy and Hydrodynamic Force ...... 16 2.2.3 Empirical Criterion of Clausen and Clark (1990) for Masonry Buildings ...... 18 2.2.4 Smith’ Empirical Criterion (1991) ...... 19 2.3 Comparison Between Different Criteria ...... 21 References ...... 24 3 Flood Impact on Human Beings Stability ...... 25 3.1 Introduction ...... 25 3.2 Models of Human Beings Stability ...... 25 3.2.1 Empirical USBR Approaches ...... 26 3.2.2 Semi-empirical Approach ...... 26 3.2.3 Laboratory Tests at Helsinki University of Technology ...... 30 3.2.4 Comparison of Results and Envelope Threshold ...... 31 3.2.5 Conceptual Physically-Based Approaches ...... 35 References ...... 42 4 Flood Impact on Mobilizable Objects ...... 45 References ...... 48 5 Global Criteria for Impact Estimation ...... 49 5.1 Introduction ...... 49 5.2 New South Wales (Australia) Criteria ...... 49 5.3 ESCAP Criteria ...... 49

xi xii Contents

5.4 CEDEX (Spain) Criteria ...... 50 5.5 Indications of Po River Catchment Authority (Italy) ...... 51 5.6 FEMA (USA) Criteria ...... 52 5.7 Comparison of Different Approaches ...... 54 References ...... 56 6 Hydrodynamic Criteria for Impact Evaluation ...... 57 6.1 Introduction ...... 57 6.2 Hydrodynamic Thresholds ...... 57 6.3 Implementation of Hydrodynamic Thresholds ...... 60 6.3.1 Reference Values ...... 60 6.3.2 Implementation Methods ...... 61 6.3.3 Hydrodynamic Threshold Water Depth–Slope ...... 62 6.3.4 Use of Hydrodynamic Thresholds on the Basis of the Tolerance of the Results of Hydraulic Studies ...... 64 References ...... 68 7 Flood Proofing Methods ...... 69 7.1 Overview ...... 70 7.1.1 Alternative Ways of Protecting Urbanized Lands from Floods ...... 71 7.1.2 Flood Proofing Role ...... 72 7.1.3 Flood Proofing Options and Disciplinary Relations .... 74 7.2 First Level Classification (Strategic Planning) ...... 76 7.2.1 Permanent Techniques ...... 77 7.2.2 Temporary Techniques ...... 91 7.2.3 Small Permanent Techniques ...... 93 7.3 Design and Assessment Principles: Introduction ...... 94 7.4 Temporary Flood Proofing as an Emerging Strategy for Adaptation and Regional Resilience ...... 99 7.4.1 Defending the Value of Property Investment ...... 102 7.5 Insurance Discount, Premium Reduction and Tax Handle ..... 103 References ...... 106 8 Temporary Flood Proofing Techniques Planning ...... 109 8.1 Approach to Arrangement and Activation ...... 109 8.2 Decision Factors: The SENSO Model ...... 111 8.3 Temporary Flood Proofing Response Planning ...... 113 8.4 Defence Lines ...... 115 8.4.1 Positioning ...... 115 8.4.2 Water Reaction Assessment and Connected New Flood Prone Areas ...... 118 8.4.3 Deployment ...... 120 8.4.4 Comprehensive Logical Scheme for the Use of Temporary Flood Proofing...... 124 8.5 A Notable Requirement Case: Pisa (Italy)—Or Where, Probably, the Modern Temporary Flood Proofing Was Started . . 124 Contents xiii

8.6 Effectiveness Analysis: A Path Towards Better Design Procedures ...... 131 References ...... 140 9 Temporary Flood Proofing Devices Analysis ...... 141 9.1 Recapitulating ...... 141 9.2 Description of Temporary Flood Proofing Proposed Classes .... 143 9.2.1 C.R.1 (Floodwalls Removable Group 1): Stacking of Individual Base Units Filled with Solid Materials Acting by Gravity ...... 143 9.2.2 C.R.2 (Floodwalls Removable Group 2): Supportive/ Juxtaposed Use of Fluid Containers ...... 156 9.2.3 C.R.3 (Floodwalls Removable Group 3): Self-Deploying or Self-Supporting Mobile Barriers . . . . 167 9.2.4 C.R.4 (Floodwalls Removable Group 2): Emergency Dikes and/or Berms of Loose/Free Solid Material . . . . . 175 9.2.5 C.P.1 (Floodwalls Pre-arranged/Pre-located Group 1): Temporary Barriers/Shields with Especially Crafted Anchoring (Temporary Waterwalls) ...... 181 9.2.6 C.D.1 (Floodwalls Demountable Group 1): Fixed Retractable Barriers ...... 189 9.2.7 D.R.1 (Dry Flood Proofing Removable Group 1): Full Dry Flood Proofing of Buildings ...... 196 9.2.8 D.P.1 (Dry Flood Proofing Pre-arranged/Pre-located Group 1): Selective Dry Flood Proofing with Customised Watertight Protection ...... 202 9.2.9 D.D.1 (Dry Flood Proofing Demountable Group 1): Selective Dry Flood Proofing with Demountable Watertight Protections ...... 209 9.2.10 D.R.2 (Dry Flood Proofing Removable Group 2): Complementary Dry Flood Proofing of Buildings by Means of Removable Universal Apparatus ...... 212 9.2.11 C/D.1 (Floodwalls and Dry Flood Proofing Temporary Complements Group 1): Mixed Solutions and Special Cases ...... 218 9.2.12 E.R.1 (Wet Flood Proofing Temporary Complements Group 1): Hydro-repellent Sacs or Similar Protections Systems for Indoor Movable Goods ...... 219 9.2.13 G.R.1 (Ground Lowering/Levelling of Free Land Temporary Complements Group 1): Water Diversion Temporary Activated Pipes or Bridges ...... 221 9.3 Emergency Flood Proofing Techniques as ‘Transitional Solutions’ to Support Adaptation Policies Towards Urban Redevelopment and Building Restoration ...... 222 References ...... 223 Websites ...... 224 xiv Contents

10 Tests, Guidelines and Norms ...... 225 10.1 Overview ...... 225 10.2 Single Building Defence (Inner Line of Defence) ...... 225 10.2.1 USA Approaches ...... 225 10.2.2 Australian Guidelines ...... 229 10.2.3 European Guidelines ...... 234 10.3 Areal Defence ...... 240 10.3.1 FM Approval Standard ...... 240 10.3.2 SMARTeST Project, Flood Resilience Technologies ...... 243 10.3.3 Performance Evaluation About Protection Devices According to CSTB ...... 252 10.3.4 DEFRA/Environment Agency ...... 257 10.3.5 Temporary Defences According to VKF ...... 259 10.4 Other Documents ...... 259 10.4.1 Emergency Preparedness Canada ...... 259 10.4.2 APFM Global Programme ...... 262 10.4.3 ASTM International ...... 263 10.4.4 Guidelines for Tokyo Underground Structures ...... 263 References ...... 266 World Wide Web ...... 266 Other References ...... 267 Chapter 1 Introduction

In the context of natural disasters, the scientific community agrees that risk is the product of the probability of a hazard and its adverse consequences. There is no risk if there are no people or values that an extreme event can strike. Similarly, an event is only termed a catastrophe if it hits people and/or it damages their possessions. The intensity and frequency of a natural phenomenon (hazard) is only one of three factors that determine the overall risk. The amount of values present in the area concerned (exposure) as well as their loss susceptibility (vulnerability) are crucial for the resulting risk. Hence, one can express the risk formula as a function of these three quantities. If risk is insured, a fourth factor, insurance penetration, also plays a role. All factors that determine the risk are variable. While man cannot influence occurrence and intensity of a natural phenomenon, one may reduce ground effects by land use, agricultural practices and engineering works; and we may control the exposure, e.g. by avoiding hazard-prone areas. One can reduce vulnerability by increasing the structural resistance of objects, with measures depending on specific hazard, e.g. floodplain propagation, flash flood surge or mudflow. Insurance penetration generally increases the geographical spread of risks, but may also increase the probability of higher accumulation losses. The current approaches deal with analyzing these factors separately, and merging the results under a purely holistic framework. The major objective is ranking risk levels under a merely geographical perspective. The approach further takes the assumption of mutually independent factors as a postulate without exploring their mutual relations also in designing remediation measures. Thus, actions reflect this approach; and risk reduction projects do not account for complexity nor provide a comprehensive fusion to integrate hazard reduction, exposure conscious planning, and enhancements to decrease vulnerability. Is the approach satisfactory? Mainstream thinking states that flood-risk-related science and technology requires further amelioration in computational practices, decision-making procedures, topographic detail, observational facilities, and so on. That is, one must travel the conventional routes only, assuming that the roads not taken are no exit roads, definitely. Is it time to overcome this assumption?

No doubt, in last 50 years hydrological science improved both knowledge of underlying physical processes and computational capability to achieve detailed information on hazard and provide predictions in both real-time and long-term scenarios. Flood management, economy and post-catastrophe recovery practices are much more sophisticated than those available 50 years ago. In spite of fundamental advances in many disciplines involved in flood assessment meteorology, flood hydrology, risk assessment, water engineering, urban planning, disaster related social assessment flood catastrophes are increasingly challenging human society worldwide. Data display an increasing challenge to man’s file all around planet Earth. Floods have caused the largest portion of insured losses among all natural catastrophes during recent decades, causing losses worth USD55 billion in 2016 alone around the world. The updated report by European Environment Agency (Floodplain management: reducing flood risks and restoring healthy ecosystems, 2016) examined data on floods dating from 1980 to 2010, and found significant increases in flooding, which will only get worse as time goes on. In addition, by 2050 flood losses may increase fivefold, because of climate change, of increasing value of land around the floodplains, and of urban development. People in coastal areas are more aware of flood threats than those living in inland flood zones; and populations in inland areas are increasing in USA (Qiang et al. 2017). Preliminary estimates for insured global losses resulting from natural and manmade disasters in 2017 are around USD136 billion, well-above the annual average of the previous 10 years, and the third highest since sigma records began in 1970. Total economic losses soared in 2017 to USD306 billion from USD188 billion in 2016. The accumulation of economic and insured losses ramped up in the second half of the year, due primarily to the three hurricanes Harvey, Irma and Maria that hit the US and the Caribbean, and wildfires in California. Globally, more than 11,000 people have died or gone missing in disaster events in 2017, similar to 2016. Extreme weather in the US led to a high number of severe convective storms (thunderstorms). Five separate severe thunderstorm events from February to June caused insured losses of more than USD1 billion each. The most intense and costly event was a 4-day long storm in May with heavy damage to property inflicted by hail in Colorado and strong winds in other parts of southern and central states. The economic losses of this storm alone were USD2.8 billion, with insured losses of USD2.5 billion (see, Swiss Re, Preliminary sigma estimates for 2017: global insured losses of USD136 billion are third highest on sigma records, 2017). Global warming is a not negligible forcing factor of flood hazard, capable of augmenting flood risk in the next future. Cities are particularly vulnerable to climate risks due to their agglomeration of people, buildings and infrastructures. Guerreiro et al. (2018) assessed future changes in flood impact for all 571 European cities in the Urban Audit database using a consistent approach. To capture the full range of uncertainties in natural variability and climate models, they used all climate model runs from the Coupled Model Inter-comparison Project Phase 5 to calculate Low, Medium and High Impact scenarios, which correspond to the 10th, 50th and 90th percentiles of each hazard for each city. For the low impact scenario, drought 1 Introduction 3 conditions intensify in southern European cities while river flooding worsens in northern European cities. However, the high impact scenario predicts that most European cities will see increases in both drought and in river flood risks. Over 100 cities are particularly vulnerable to two or more climate impacts. Moreover, the magnitude of impacts exceeds those previously reported, highlighting the substantial challenge cities face to manage future climate risks, as further shown by Alfieri et al. (2018): “A considerable increase in flood risk is predicted in Europe even under the most optimistic scenario of 1.5 C warming as compared to pre-industrial levels, urging national governments to prepare effective adaptation plans to compensate for the foreseen increasing risks”. Peduzzi et al. (2009) showed that human vulnerability from natural disasters is mostly linked with country development level and environmental quality. Some social groups display higher vulnerability than others in both developed countries (Cutter and Finch 2008; Fekete 2009; Dzialek et al. 2016) and developing ones (Adger 2006; Rasch 2015; Salami et al. 2017). Are these factors properly accounted when developing vulnerability, exposure and hazard reduction plans and projects? The interactions among natural hazard, man-made risk enhancements and social issues are not straightforward. For example, Hispanic immigrants have the greatest likelihood, and non-Hispanic Whites the least likelihood, of residing in a flood prone zone in Houston, Texas, USA; conversely, in Miami (Florida, USA) non-Hispanic Whites have a significantly greater likelihood of residing in a flood zone when compared to Hispanic immigrants (Maldonado et al. 2016). Risk perception itself is subject random attitudes, as shown by a recent assessment of social vulnerability in the most flood-prone country of Africa (Kablan et al. 2017). One must notice: “man’s attitude against flood risk over last 150 years cannot be disjointed from country’s cultural and social attitude, this including politics and religion throughout history” (Rosso 2017). This applies to the most disaster-prone country of Europe, Italy (Dickie et al. 2002). However, one can apply this concept to major flood disasters in Europe and United States (e.g. the Great Flood of Paris in 1910 or the Katrina catastrophe in 2005) as well as to those occurred in Far Eastern countries [e.g. the deadliest dam disaster of Banqiao in China (1975) or the 2016 Assam flood in India]. From ancient times, major floods have an impact on culture, politics and religion (Seppilli 1979) and the feedback involves manmade modification that affect hazard, exposure and vulnerability. One should envisage that a novel approach should consider qualitative and quantitative knowledge under a comprehensive and coherent framework to ameliorate man’s capability to cope with floods. The mutual relation between hazard, exposure and vulnerability is usually missed by current approaches, although it has a clear influence in risk assessment (Danielsson and Zhou 2016). There is the need for merging knowledge from different areas, e.g. hydrology and social sciences (Sivapalan et al. 2012; Di Baldassarre et al. 2015; Gober and Wheater 2015) or ecology and hydrology (Eagleson 2002; D’Odorico and Porporato 2006; Good et al. 2015). However, complexity arising from these interactions requires a step-ahead, because traditional quantitative approaches cannot properly provide an insight of the mechanisms and feedbacks involved, independently from deterministic or stochastic methods adopted in the 4 1 Introduction challenge. When investigating the apparent chaos that arise between nature and man, one must take in mind the famous statement by Henry Adams “Chaos was the law of nature; Order was the dream of man”. Are the present knowledge and state-of-the art mathematical methods capable to provide the most efficient information on hazard? Is urban planning aware that floods are the first thread among natural disasters? Is there enough and coherent perception of vulnerability by the multifaceted environmental, social and political stakeholders? Trends observed in new millennium worldwide provide a negative answer. In addition, urban resilience (Godschalk 2003) is still a missed issue in urban planning and management in spite of the strong acceleration of urbanization worldwide. In order to mitigate flood risk, resilience plays a major role if one must properly address the challenge by climate change (Klein et al. 2003): The concept of adaptive capacity, which has emerged in the context of climate change, can then be adopted as the umbrella concept, where resilience will be one factor influencing adaptive capacity. This improvement to conceptual clarity would foster much-needed communication between the natural hazards and the climate change communities and, more importantly, offers greater potential in application, especially when attempting to move away from disaster recovery to hazard prediction, disaster prevention, and preparedness. In particular, one must approach resilience at two different scales: the regional scale and the local scale, the latter in opposition to the concept of resistance. As introduced below, three main factors assess the risk due to catastrophic events of natural origin, i.e. hazard, exposure and vulnerability. 1. Hazard, H, is the probability that a phenomenon with a given intensity I will occur in a given period of time and in a given area: H ¼ H(I). 2. Vulnerability, V, is the level of the losses caused to a given element or to a given group of elements which can be affected by phenomena of a given intensity, as a function of such an intensity I and of the kind of element E at risk: V ¼ V(I, E). 3. Exposed Value, W, that is the economic value or the number of units, related to each one of the elements at risk in a given area and depending on the kind of elements: W ¼ W(E). The total risk, R, related to a particular element at risk E and to a given intensity I, is the result of a convolution like R(E, I) ¼ H(I)*V(I, E)*W(E). In general, R is the expected value of the losses in terms of human lives, wounded persons, damages to properties and interferences with economical activities due to the occurrence of a particular phenomenon of a given intensity. This book addresses flood vulnerability under a comprehensive but problem oriented approach to reduce it in urban areas. The key measure to decrease flood vulnerability is flood proofing. The primary objective of flood proofing is to reduce or avoid the impacts of coastal ad river flooding upon structures and infrastructures. This may include, for instance, elevating structures above the floodplain, employing designs and building materials that make structures more resilient to flood damage, and preventing floodwaters from entering structures in the flood zone, amongst other 1 Introduction 5 measures. It includes any combination of structural and nonstructural additions, changes, or adjustments to structures and infrastructures, which reduce or eliminate flood damage to real estate or improved real property, water and sanitary facilities, energy and communication networks, structures and their contents. An obvious extension of flood proofing deals with dense human settlements with continuous urbanized areas, both residential and non-residential, because a single block or multiple blocks can be flood proofed under a unified approach. This plays a major role in reducing flood damage in ancient cities with historic buildings under the commitment of preserving heritage and landmarks. Developing an appropriate flood proofing strategy for protecting property (and people) from flood hazards requires evaluation of the risks, technical considerations, costs, and personal preferences. (a) First appropriate regulations must be issued at the municipal scale and municipal building officials must be aware of the need to disseminate information and guidelines, and to avoid or balance conflicting issues among stakeholders. If an existing building in the regulated floodplain has been substantially damaged or is substantially improved, regulations require that the entire structure be brought into compliance with current floodplain development standards, which precludes the use of some flood proofing techniques. Other building code requirements will also apply to the project. (b) The accurate assessment of hazard plays a fundamental role in developing the appropriate flood proofing technique under a well-assessed municipal strategy. The desired depth of flood protection is a central consideration, since both the technical challenges and the costs for flood proofing measures may increase with water depth. The potential for high water velocities, scouring, ice, and debris flows should also be taken into account. The amount of warning time must also be considered, because protective measures that require time to implement are not appropriate if the area is prone to flash flooding. (c) One must address the identification of feasible options after assessing an operative and detailed knowledge base on flood processes. The applicability of any flood proofing technique depends on the nature of the flood hazard (depth, velocity, debris potential, warning time), site characteristics (size, location, slope, soil type), and building or block characteristics (structural condition, type of foundation, type of building construction). (d) The accomplishment of flood proofing initiatives must involve the overall economic capacity of citizens to afford the costs to install and maintain flood proofing facilities over a long time horizon. Accordingly, one must clearly assess the costs and benefits. Some flood proofing options may be too costly and others may not provide the desired amount of risk reduction. (e) Finally, flood proofing requires developing a strategy for managing flood risks. The decision regarding a flood proofing project must also be based on the personal preferences and concerns of the people who will be living with the results on a day-to-day basis. Are there aesthetic preferences? Concerns about the accessibility of the building? Special considerations related to historic structures? Would someone be available and able to implement protective measures prior to a flood? How much risk are you willing to live with? One must merge these considerations with technical and financial assessments to develop the most appropriate strategy for managing the 6 1 Introduction

flood risks in a particular situation (Southern Tier Central Regional Planning and Development Board 2017). Flood proofing is quite popular in those countries where flood insurance is a major mitigation measure because of nation-wide politics. For example, in an effort to restore fiscal soundness to the National Flood Insurance Program, the Congress of the United States of America enacted program reforms in July 2012. These changes resulted in dramatically higher flood insurance costs for many policyholders, which led to additional reforms in March 2014. As a result, insurance subsidies are being phased out for older buildings that do not comply with current floodplain development standards. The objective is to move toward “full-risk rate” premiums that reflect the flood risk for each building. The impact of these reforms is minor for some policyholders, but it could result in significantly higher insurance costs for others. Accordingly, subsidized rates mitigation push to consider options using updated flood proofing measures and facilities. In Europe, facing with floods was generally in last two centuries. After the great floods such as those devastating Wien in 1847, Rome in 1870, Paris in 1910, London in 1928, Florence in 1966, Prague in 2002 huge engineering works were carried out to reduce flood hazard. These are partially successful, because they actually reduced flood hazard and the cities did not suffer destructive impacts as those mentioned, but recent events (e.g. Paris in 2016, Rome in 1937 and 2014) show that further measures are needed to achieve acceptable risk levels, but both physical and economic issues indicate that engineering works can hardly accomplish these goal. In this context, adaptation efforts should give priority to measures targeted at reducing the consequences of hazardous events, rather than trying to avoid their occurrence. This will include a deeper insight of the dynamic behavior of floodplains as human-water systems (Di Baldassarre et al. 2013). As stated by Alfieri et al. (2017) “The adaptation efforts should favor measures targeted at reducing the impacts of floods, rather than trying to avoid them. Conversely, adaptation plans only based on rising flood protections have the effect of reducing the frequency of small floods and exposing the society to less-frequent but catastrophic floods and potentially long recovery processes”. Relocation would provide the most effective results, but it has human costs that European countries can afford under extensive and pervasive policies. Under the adaptation commitment, the reduction of vulnerability appears to be an effective and realistic measure towards flood risk mitigation from country-aggregated data for Germany, France, United Kingdom and Italy (see Fig. 1.1). An interesting overview of the important integrated aspects of flood proofing in urban areas comes up also from the quite recent English manual on flood hazard edited by Lamond et al. in 2011. As a matter of fact, flood proofing refers to a large number of interventions, these including building repositioning or lifting, dry or wet flood proofing of the buildings, self-mobile barriers, emergency dikes and/or berms and even the old-fashioned sand sack walls. All of those flood proofing measures or devices aimed to reduce or at least to control the flood effects at a local or areal scale, due to people loosing stability when hit by the flow, buildings damaged by water flow, vehicles and other materials mobilized and transported by water stream during 1 Introduction 7

Fig. 1.1 Beneﬁts of four adaptation strategies on ensemble annual estimates of population affected (left) and expected damage (right) in Europe in time slice 2020, 2050 and 2080 (adapted from: Alﬁeri et al. 2017)

flood conditions. Because most people developed flood proofing measures under holistic approaches, the book first approaches physics of stability and instability of both human beings, objects and buildings under flood attack, this including possible criteria to evaluate stability and safety (see Chaps. 2–6). 8 1 Introduction

Chapter 7 provides an updated classification of possible flood proofing methods and devices under a strategic planning perspective. Both temporary and permanent measures are considered, and the specific situations for effectiveness. Then, we focalize on temporary flood proofing techniques, which display the best performance in terms of cost-benefits. A number of practical examples are presented, most of them are real case studies, without mentioning manufacturers or commercial product names. Finally, we address economic issues associated with insurance discount, premium reduction and tax handle. Chapter 8 deals with planning of temporary flood proofing measures. We discuss arrangement and activation approaches, this including decision-making to be addressed under a coherent modeling framework. One must consider possible flooding scenarios in order to implement suitable flood proofing system. This is described in detail using a case study for a historic landmark in Italy, the city of Pisa. Chapter 9 provides an extensive review of state-of-the-art device and facilities suitable for temporary flood proofing developments. Chapter 10 reports a review of Tests, Guidelines and Norms adopted by different countries where flood proofing is currently implemented. This can help encouraging authorities, municipalities, technicians, stakeholders and end users to improve their capability to cope with floods under the goal of reducing vulnerability at the municipal, block and building scales.

References

Adger WN (2006) Vulnerability. Glob Environ Change 16:268–281 Alfieri L, Feyen L, Di Baldassarre G (2017) Increasing flood risk under climate change: a pan-European assessment of the benefits of four adaptation strategies. Clim Change 136:507–521 Alfieri L, Dottori F, Betts R, Salamon P, Feyen L (2018) Multi-model projections of river flood risk in Europe under global warming. Climate 6(1):6 Cutter SL, Finch C (2008) Temporal and spatial changes in social vulnerability to natural hazards. Proc Natl Acad Sci USA 105(7):2301–2306 Di Baldassarre G, Kooy M, Kemerink JS, Brandimarte L (2013) Towards understanding the dynamic behaviour of floodplains as human-water systems. Hydrol Earth Syst Sci 17:3235–3244 Di Baldassarre G, Viglione A, Carr G, Kuil L, Yan K, Brandimarte L, Blöschl G (2015) Debates- perspectives on socio-hydrology: capturing feedbacks between physical and social processes. Water Resour Res 51(6):4770–4781 D’Odorico P, Porporato A (eds) (2006) Dryland ecohydrology. Springer, New York Danielsson J, Zhou C (2016) Why risk is so hard to measure. SSRN Electron J. https://doi.org/10. 2139/ssrn.2597563 Dickie J, Foot J, Snowden F (eds) (2002) Disastro! Disasters in Italy Since 1860: culture, politics, society. Palgrave Macmillan, New York Dzialek J, Biernacki W, Fieden L, Listwan-Franczak K (2016) Universal or context-specific social vulnerability drivers – understanding flood preparedness in southern Poland. Int J Disaster Risk Reduct 19:212–223 Eagleson PS (2002) Ecohydrology: Darwinian expression of vegetation form and function. Cambridge University Press, Cambridge References 9

Fekete A (2009) Validation of a social vulnerability index in context to river-floods in Germany. Nat Hazards Earth Syst Sci 9:393–403 Gober P, Wheater HS (2015) Debates-perspectives on sociohydrology: modeling flood risk as a public policy problem. Water Resour Res 51:4782–4788 Godschalk DR (2003) Urban hazard mitigation: creating resilient cities. Nat Hazards Rev 4 (3):136–143 Good SP, Noone D, Bowen G (2015) Hydrologic connectivity constrains partitioning of global terrestrial water fluxes. Science 349:175–177 Guerreiro SB, Dawson RJ, Kilsby C, Lewis E, Ford A (2018) Future heat-waves, droughts and floods in 571 European cities. Environ Res Lett 13(3):034009 Kablan MKA, Dongo K, Coulibaly M (2017) Assessment of social vulnerability to flood in urban Cote d’Ivoire using the MOVE framework. Water 9:292 Klein RJT, Nicholls RJ, Thomalla F (2003) Resilience to natural hazards: how useful is this concept? Environ Hazards 5:35–45 Lamond J, Booth C, Hammond F, Proverbs D (eds) (2011) Flood hazards: impacts and responses for the built environment. CRC Press, Boca Raton, 387 pp Lorenzo Alfieri, Francesco Dottori, Richard Betts, Peter Salamon, Luc Feyen, (2018) Multi-Model Projections of River Flood Risk in Europe under Global Warming. Climate 6 (1):6 Maldonado A, Collins TW, Grineski SE, Chakraborty J (2016) Exposure to flood hazards in Miami and Houston: are Hispanic immigrants at greater risk than other social groups? Int J Environ Res Public Health 13(8):755 Peduzzi P, Dao H, Herold C, Mouton F (2009) Assessing global exposure and vulnerability towards natural hazards: the disaster risk index. Nat Hazards Earth Syst Sci 9:1149–1159 Qiang Y, Lam NSN, Cai H, Zou L (2017) Changes in exposure to flood hazards in the United States. Ann Am Assoc Geogr 107(6):1332–1350 Rasch RJ (2015) Assessing urban vulnerability to flood hazard in Brazilian municipalities. Environ Urban (IIED) 28(1):145–158 Rosso R (2017) Bombe d’acqua: Alluvioni d’Italia dall’Unita al Terzo Mil- lennio (Rainbombs: floods in Italy from Unity to the third millennium). Marsilio, Venice Salami RO, Von Meding JK, Giggins H (2017) Urban settlements’ vulnerability to flood risks in African cities: a conceptual framework. Jamba: J Disaster Risk Stud 9(1):a370 Seppilli A (1979) Sacralità dell’acqua e sacrilegio dei ponti - Seconda Edizione [Sacredness of water and sacrilege of bridges - Second Edition]. Sellerio, Palermo Sivapalan M, Savenije HHG, Blöschl G (2012) Socio-hydrology: a new science of people and water. Hydrol Process 26:1270–1276 Southern Tier Central Regional Planning and Development Board (2017) Floodproofing: protect your property from flood damage. http://www.stcplanning.org/index.asp?pageId¼107 Chapter 2 Flood Impact on Buildings

2.1 Introduction

A building stressed by water flow is affected by three main actions: (i) buoyancy, (ii) hydrostatic force, (iii) hydrodynamic force. The first one, sometimes also called Archimedes force, is due to the tendency of a submersed building to float because of the weight of the water that could be in its volume. The second one is due to the mass of water as (statically in quiet) that is in direct contact with the structure, it is isotropic and its direction is locally perpendicular to the contact surface, causing effects on both the vertical elements of the structure (walls, pillars and so on) and on the horizontal elements of the structure (girders, roofs and so on). The third one is provided as the result of the forces related to the water movement and affects the upstream surface of the structure, that is the surface directly facing the flow: it tends to drag the structure toward the flow direction and to scour the foundations, with an additional destabilizing effect due to local whirling eddies and possible negative pressure on the downstream surfaces of the structure. Until now, literature has not yet payed a lot of attention to the study of the effects of flooding events on single buildings and on residential, industrial and commercial areas in general (Smith 1994). To ensure the structural safety of the buildings towards flooding phenomena by means of consolidation measures specifically designed to this aim, it must be kept into account that such measures are effective and economically viable only when the flow velocities don’t exceed 3 m/s (Lardieri 1975).

2.2 Evaluation Criteria 2.2.1 Analysis of Stormwater Effects

Sangrey et al. (1975) developed a procedure to forecast the interactions between ﬂood water and structures in the inundated plan, on the basis of the experience of the

© Springer Nature Switzerland AG 2019 11 D. F. Bignami et al., Flood Proofing in Urban Areas, https://doi.org/10.1007/978-3-030-05934-7_2 12 2 Flood Impact on Buildings inundation in the Chemung watershed (Elmira, NY, USA) caused by the Agnes cyclone in 1972. Hence, they analysed 155 buildings and structures of different kinds, out of the more than 1000 ones existing there. In particular, nine categories have been defined according to their weight W, of course approximated (Table 2.1). The assessment of the damages was carried out by examining both of the available aerial photos in a detailed way and by ground surveys (recognition of the structures and interviews with the inhabitants). So, the buildings and the structures have been classified according to just a binary criterion: either survived or destroyed. Then, the hydrodynamic characteristics of the inundation, in terms of velocity U and water depth h, have been simulated by means of a standard 1D model, that is HEC-2, modified in order to take into account the effects of the structures on both soil roughness and cross section shape. So the maximum values of U and h have been found out for each structure in the watershed. The stream creates both a horizontal load and a vertical load against a flooded structure. In particular, the horizontal load FH is given by the drag along the flow direction, expressed by Sangrey et al. (1975) as: ÀÁ 2 FH ¼ CDðÞ1=2 ρU bhÀ h fo ð2:1Þ

3 where CD is the drag coefficient, assumed equal to 2; ρ is the water density as kg/m ; U is the stream velocity as m/s, b is the structure width in the direction orthogonal respect to the flow as m; h is the water depth as m, and hfo is the foundation depth as m. The load on the foundation is neglected, because the damages are usually due to the separation between the emerging structure and the foundation itself; moreover the stabilizing effects due to minor connections (nails, screws, wires, and so on) between those two elements are negligible. The analysis is focused on the relationship between the lateral load, represented by the adimensional drag parameter FH/W, and the corresponding normal load, represented by the di buoyancy parameter (h À hfo)/(10s), where s indicates the number of the floors in the structure under analysis. The results are shown in Fig. 2.1, which shows a quite sharp separation between the destroyed buildings (black points) and the buildings that survived (white points). Figure 2.1 also shows how it is possible to find an empirical criterion about the damage, based on the parameters

Table 2.1 Classification of the structures according to Sangrey et al. (1975) Type Description Weight (kgf) A1floor building, light wood-made structure 7800 B1floor building, heavy wood-made structure 11,100 C 1 and ½ floor building, light wood-made structure 11,100 D 1 and ½ floor building, heavy wood-made structure 16,300 E2floors building, light wood-made structure 12,300 F2floors building, heavy wood-made structure 18,800 G Light wood-made 1 floor appendices (garage and similars) 1000 H, V 1 or 2 floors structures, concrete made Individual assessment 2.2 Evaluation Criteria 13

Fig. 2.1 Results of the experimental investigation and consequent empirical criterion about damage assessment according to Sangrey et al. (1975)

FH/W and (h À hfo)/(10s): for example, if the buoyancy parameter is equal to 0.8 and the parameter FH/W is equal to 1, the structure is likely to be destroyed during a flood. A study by Lorenzen et al. (1975) examined 15 farms flooded by the same Agnes cyclone in 1972 in four different watershed of the State of New York, each one consisting of a number of buildings between 1 and 4. The structures of the buildings under analysis (were both wood-made, metal-made and concrete-made). The flooding characteristics (water depth and water velocity, that reached 1.5 m/s) had 14 2 Flood Impact on Buildings been estimated on the bases of both eye-witnesses and flood evidences, as the surface water levels were marked on some of the walls by the inhabitants. The analysis includes the assessment of: 1. Floating thresholds for the wood-made buildings, 2. Static and dynamic pressures, 3. Collision load and debris flow impact load assuming that the buildings are not anchored to their foundations. The floating line of a typical single floor ranges between the ground floor and a little bit more than 1 m above the foundation platform. Nevertheless, the wooden buildings and mobile buildings tend to float in a vertical direction, so a building that is not anchored can be removed from its foundations well before the floating condition is achieved. On the contrary, buildings made of concrete do not float but tend to slip and to roll. The hydrostatic pressure due to the flood water has a high capacity to drag and destroy walls (of) basement floor, especially if such walls are sealed. The water pressure in the saturated soil in subbasement with a deep of 1.8 m can reach, at the floor level and below the pavement, about 1800 kgf/m2: this is enough to lift the pavement, creating large cracks in the walls, deforming and even breaking them. In Fig. 2.2 you can see the comparison between the hydrodynamic pressures due to flood waters and to winds. In the examined area of the State of New York, the wind velocity for a return period of 50 years is estimated to be equal to about 31 m/s while for a return period of 100 years it becomes 37 m/s. As a wind velocity of a 31 m/s causes the same pressure of a water flow having a velocity of 1.1 m/s, this means that a building resisting such a velocity should be able to cope with a stream flow characterized by this velocity. In Fig. 2.3 you see the impact action due to a floating wooden rafter of 45 kgf. Moreover, if the value is 90 kgf and the velocity is about 0.9 Ä 1.2 m/s that is enough to penetrate a wall made of wood, to crack 5 Â 10 cm pillar or to damage a concrete wall.

Fig. 2.2 Comparison 2.5 50 between the pressure values 45 ﬂ due respectively to ood 2.0 40 water velocities and wind 100 year recurrence storm 35 velocities [from: Maijala 50 year recurrence storm 1.5 30 (2001), based on Lorenzen et al. (1975)] 25 1.0 20 15 0.5 10 water velocity (m/s) 5 wind velocity (m/s) 0.0 0 0 500 1000 1500 pressure (Pa) water wind 2.2 Evaluation Criteria 15

500 Wood framed structure. Assumed deflection: 5.1 cm to failure Masonry structure. Assumed deflection: 1.2 cm to failure 400

300

200 impact force (kgf)

100

0 0.0 0.5 1.0 1.5 velocity (m/s)

Fig. 2.3 Action due to a ﬂoating wood made rafter [from: Maijala (2001), based on Lorenzen et al. (1975)]

Definitively, the study of Hurricane Agnes creates the following conclusions. Metal Structure Buildings Those buildings (garages, stockrooms and so on) usually survive without too much damage. Nevertheless, the stream flow can drag them, while both floating materials and sediment transport can damage their perimeter. But a solid anchoring of their pillars to the foundation and the empty interblocks of such buildings (if present) tend to mitigate the inundation damages. The buildings with a light metal structure, without impervious walls, with good foundations and effective anchorage, suffer minor damage, essentially because they allow the hydrostatic pressure to become equal on both sides of the structural elements. Wooden Made Buildings with Concrete Foundations These buildings have very different kinds of reactions to flooding events. As they are usually quite light, in comparison to water, the buoyancy can cause their structural failure. The main reasons for their structural failure are due to insufficient foundations and inadequate anchorage, while the damages observed in buildings that are solidly anchored to strong foundations are quite limited. Concrete Made Buildings They can resist quite well to an inundation event if they have solid foundations and, at the same time, are not influenced by buoyancy. However, many basement walls are subject to damages because they are sealed and do not allow for the hydrostatic pressure to be equalized until cracks are created in the walls. It is also important to note that concrete foundations and other elements made of concrete are far less resistant in comparison to similar elements reinforced by concrete. 16 2 Flood Impact on Buildings

Table 2.2 Threshold values of the submergence water depth for floating (Black 1975) Kind One floor (m) One floor and a half (m) Two floors (m) Light 1.9 2.7 2.9 Heavy 2.8 3.5 4.7 Heavy with masonry stiffenings 5.2

2.2.2 Buoyancy and Hydrodynamic Force

To evaluate the buoyancy effect, Black (1975) studies three different kinds of small buildings made of wood (with respectively one floor, one floor and a half, and two floors) anchored to a foundation platform of 7.3 Â 9.8 m. For each kind of building, two different construction techniques are considered, light and heavy. Their overall weight varies between 7100 and 17,000 kgf. Moreover, the additional effect due to masonry stiffenings made of bricks is examined. A building begins to float when the buoyancy exceeds the weight. As the buoyancy is a function of the submergence water depth and, Table 2.2 shows the results in terms of water depth threshold, that is buoyancy equal to weight. It can be seen that light houses start to float when the submergence is equal to about half time their height, while the heavy houses when the submergence is equal to about 3/4 times their height. In addition, Black (1975) studied the combination of buoyancy and dynamic force, in order to assess the relationship between velocity and water depth in terms of building threshold stability. The results summarized in Fig. 2.4 shows how the buildings become unstable because of the combination of those two effects. A flow rate of 1.8 m/s creates a dynamic pressure of 1.7 kPa: likely, it is enough to create structural damages to the different components of the building and erodes the foundations in a significant way, as the foundation soil usually is not able to resist a velocity higher than 1.5 m/s for more than 1 h. Figure 2.5 summarizes the calculations of the bending moment due to the combination of those two different actions, that are compared with the allowed values (related to the allowed stress values, that are respectively 6895 and 13,790 kPa1) usually adopted in wood made buildings. A water depth of 90 cm is enough to compromise a light building even in still water conditions! A wooden wall can sustain higher pressure, about 41,000 Ä 55,000 kPa in terms of breaking point. When the water enters a building, the hydrostatic pressure on the vertical walls becomes equal; so, Fig. 2.6 shows the relationship between the bending moment due to just the dynamic pressure. If, for example, the flow rates has a velocity of 2.4 m/s, the lower stress limit of the material is exceeded for a water depth of 1 m and the higher stress limit for a water depth of 1.6 m.

1The corresponding allowable stress values for a pilaster of 5 Â 10 cm are respectively 347 and 694 Nm. 2.2 Evaluation Criteria 17

5.0 1 story house drywall 1 story house plaster wall 4.5 1 1/2 story house drywall 4.0 1 1/2 story house plaster wall 1 1/2 story house drywall + brick veneer 3.5 2 story house drywall 3.0 2 story house plaster wall

2.5

2.0

water depth (m) 1.5

1.0

0.5

0.0 0123456789 water velocity (m/s)

Fig. 2.4 Water velocity required to move a building (9.8 m large) placed orthogonally respect to the stream ﬂow during an inundation [from: Maijala (2001), on the basis of the studies of Black (1975)]

5000 water velocity 0.0 (m/s) [hydrostatic pressure only] 4500 water velocity 1.5 (m/s) water velocity 2.4 (m/s) 4000 allowable limit 1 (houses) 3500 allowable limit 2

3000

2500

2000

1500 Bending moment (Nm) 1000

500

0 0123 Water depth (m)

Fig. 2.5 Bending moment due to hydrostatic pressure and hydrodynamic pressure [from: Maijala (2001), based on the studies of Black (1975)] 18 2 Flood Impact on Buildings

5000 water velocity 0,6 (m/s) water velocity 1,5 (m/s) 4500 water velocity 2,4 (m/s) allowable limit 1 (houses) 4000 allowable limit 2 3500

3000

2500

2000

Bending moment (Nm) 1500

1000

500

0 0123 Water depth (m)

Fig. 2.6 Bending moment due to hydrostatic pressure [from: Maijala (2001), based on the studies of Black (1975)]

Finally, Black (1975) estimates that a 20 cm wide and 2.4 m tall concrete wall collapses because of a load generating a bending moment of 280 Ä 330 Nm, while a reinforced concrete wall is about 10 times more resistant as it collapses because of a bending moment of 3900 Ä 4400 Nm. It is also necessary to take into account that walls made of concrete are often affected by crevices. Anyway, a water depth of 2.4 m creates a dangerous load even in cases of workmanlike reinforced concrete walls.

2.2.3 Empirical Criterion of Clausen and Clark (1990) for Masonry Buildings

Clausen and Clark (1990) have developed an empirical criterion to forecast the potential damages due to the break of an embankment or a dam, estimating the stream velocity U and the water depth h that occurred after the Dale Dyke dambreak in 1864 in UK, with more than 260 people having died. Detailed data about that disaster and about the consequent structural damages were already published by Harrison (1864). Clausen and Clark (1990) classiﬁed the damages according to the following categories: • Flooding: damage similar to that caused by a shallow natural water, which does not cause immediate structural damage to the buildings; 2.2 Evaluation Criteria 19

• Partial damaging: moderate damage to the structural appendices, like the breakdown of doors and windows; • Slight damaging agli elementi strutturali degli edifici, • Total destruction, caratterizzata da collasso strutturale o danni tali da rendere necessaria la demolizione e la ricostruzione degli edifici. The data reported by Clausen and Clarke (1990) are shown in Fig. 2.7 in a (V, h) chart. The criterion deduced by a specific analyses of the considered event is shown in Fig. 2.8, where the boundaries between the different damage categories (flooding, partial damage, total destruction) are determined by curves with constant U Á h,so assuming that U Á h (m2/s) is the damage discriminating parameter. The boundary between flooding and partial damage is U Á h ¼ 3m2/s, while the boundary between partial damage and total destruction is U Á h ¼ 7m2/s. Moreover, if U < 2 m/s there is just flooding without structural damage to the buildings.

2.2.4 Smith’ Empirical Criterion (1991)

Smith (1991) proposed an empirical approach, that is the criterion shown in Fig. 2.9, regarding the stability of buildings with different storeys and, therefore, different values of their own weight.

Fig. 2.7 Velocity, water depth and damage level after the inundation due to the dam break of Dale Dyke, UK (Clausen and Clark 1990) 20 2 Flood Impact on Buildings

Velocity - Water Depth Boundaries Clausen & Clarke (1990) Uh , m/s 5 2

4 7 Total disruption 3

2 Flooding Partial damages Water Depth (m) 1

0 012345 Velocity (m/s)

Fig. 2.8 Empirical criterion about the damages of the concrete made buildings according to Clausen and Clark (1990)

Fig. 2.9 Safety of the buildings as a function of the number of storeys (Smith 1991) 2.3 Comparison Between Different Criteria 21

2.3 Comparison Between Different Criteria

Figure 2.10 shows a comparison between the criterion of Sangrey et al. (1975) and the criterion of Black (1975), modiﬁed by Sangrey et al. (1975) adopting a drag coefﬁcient equal to 2 in the place of the value equal to 1 originally assumed by Black. Both the criteria refer to buildings with wooden structures and pluggings that are not anchored to the foundations. The criterion of Black is theoretical, while the criterion of Sangrey et al. is based on experimental data. It can be observed that (the)

Fig. 2.10 Comparison between two different criteria to evaluate the damages to the buildings due to ﬂooding (from: Sangrey et al. 1975) 22 2 Flood Impact on Buildings

Fig. 2.11 Comparison between the criterions of Black (1975) and the criterion of Clausen and Clark (1990) for the evaluation of the structural damages (from: Maijala 2001) is more on the safe side in comparison to the one of Sangrey et al., especially for low values of the water depth, that is for low values of the parameter (h À hfo)/(10s). Of note, the original criterion of Black, without the modification adopted by Sangrey et al., is even more on the safe side. In addition, Fig. 2.11 shows (a) comparison the original criterion of Black (1975) and the empirical criterion of Clausen and Clark (1990) developed for masonry buildings and based on experimental data. The criterion of Clausen and Clark indicates that masonry buildings are able to better cope with flooding impact in comparison to the wooden buildings. Figure 2.12 shows a further comparison, among the criterion of Clausen and Clark, the criterion of Black and the criterion proposed by the US Army Corps of Engineers (USACE) about the damages to wooden buildings and with the one of Smith (1994). The USACE criterion and the Clausen and Clark criterion and the Smith criterion (Fig. 2.9) show no significant structural damages for velocities lower than 2 m/s. But the substantial differences in the behaviour of the buildings related to the height of the buildings (that is the number of floors) expected by both USACE criterion and Smith criterion has not been seen after the empirical analysis of the Dale Dyke disaster (Clausen and Clark 1990). In this sense, the data of Sangrey et al. (1975) shows that the USACE criterion is too (poorly) on the safe side for a two story building. 2.3 Comparison Between Different Criteria 23

Fig. 2.12 Comparison between the criterions of Black (1975), Clausen and Clark (1990) and USACE or the evaluation of the structural damages (Clausen and Clark 1990)

Table 2.3 Structural safety of the buildings subject to ﬂoodings (Maijala 2001) Kind Partially damaged Totally damaged Wooden buildings Anchored U Á h 3m2/s U Á h 7m2/s Not anchored U Á h 2m2/s U Á h 3m2/s Masonry buildings U 2 m/s and U Á h 3m2/s U 2 m/s and U Á h 7m2/s

Developing the approach of Clausen and Clark (1990), following the results of the different studies reported above, the Finnish Environment Institute (Maijala 2001) recommends, for the evaluation of the safety of the buildings subject to ﬂooding, the so called criterion of the relative risk thresholds reported in Table 2.3 and shown in Fig. 2.13. 24 2 Flood Impact on Buildings

Velocity - Water Depth Boundaries Finnish Environment Institute (2001)

5 2 2 3 Uh , m /s 4 7

Wooden buildings 3

Water Depth (m) Water Depth 1

0 012345 Velocity (m/s)

Fig. 2.13 Empirical criterion of the Finnish Environment Institute—FEI (Maijala 2001)

References

Black RD (1975) Flood proofing rural residences. A Project Agnes Report, Pennsylvania New York State College of Agriculture and Life Sciences, Ithaca. Prepared for Economic Development Administration, Washington, DC, Office of Technical Assistance Clausen L, Clark PB (1990) The development of criteria for predicting dambreak flood damages using modelling of historical dam failures. In: White WR (ed) International Conference on River Flood Hydraulics, Hydraulics Research Limited, 17–20 September 1990. Wiley, Chichester, pp 369–380 Harrison S (1864) A complete history of the great flood at Sheffield on March 11 and 12, 1864 Lardieri AC (1975) Flood proofing regulations for building codes. J Hydraul Div 101(HY9):1155– 1169 Lorenzen RT, Black RD, Nieber JL (1975) Design aspects of buildings for flood plain locations. ASAE Paper, 68th Annu Meet, Davis, 22–25 June 1975 ASAE St. Joseph, Mich 20p Paper: 75- 4037. p 19 Maijala T (2001) RESCDAM: development of rescue actions based on dam-break flood analysis. Final report, grant agreement no. Subv 99/52623 Community Action Programme in the field of civil protection. Finnish Environment Institute, Helsinki Sangrey DA, Murphy PJ, Nieber JL (1975) Evaluating the impact of structurally interrupted flood plain flows. Cornell University. Prepared for: Office of Water Research and Technology. Distributed by: NTIS. PB-247 552 Smith DI (1991) Extreme floods and dam failure inundation implications for loss assessment. In: Proceedings of a Seminar “Natural and Technological Hazards: Implications for the Insurance Industry”. University of New England, Armidale, NSW, pp 149–165 Smith DI (1994) Flood damage estimation – a review of urban stage-damage curves and loss functions. Water SA 20:231–238 Chapter 3 Flood Impact on Human Beings Stability

3.1 Introduction

The relative risk of an inundation towards people submerged by a flow during a flooding depends on three factors: water depth, stream velocity and the characteristics of the ground surface. As the main cause of death for victims of a flooding is drowning (Federal Emergency Management Agency 1979), it is necessary to define the response of a humans submerged in different flow conditions. Establishing the limits for the survival of the humans also makes it easier the rescue, determining the required timeliness during the emergency. According to the Federal Emergency Management Agency (1979), a person of modest size starts to lose his/her stability when the flow reaches a water depth of a little bit less than 1 m (that is 3 ft, equal to 0.91 m) while the flow has a velocity of about 0.6 m/s (that is 2 ft/s). In this case, the parameter U Á h is equal to 0.56 m2/s (that is 6 ft2/s). But a child loses his/her stability for lower values of water depths and stream velocity. Moreover, a fast flow with a water depth of just 15 cm (that is 6 in.) can (sink) a person Federal Emergency Management Agency (1979). As a general rule, people not able to swim cannot cope with water depths higher than 1 m in flooding conditions (Roberts and Alexander 1982). It must also be taken into account that the danger affects not just the people in the flooded area but also the rescue teams.

3.2 Models of Human Beings Stability

On the basis of both the already available experimental data provided by literature and further speciﬁc laboratory tests, some Authors have proposed mathematical approaches to model human beings stability in ﬂood conditions.

It seems possible to distinguish three different stages of the development of these mathematical approaches, starting from the 1980s of the last century until today: – Empirical, – Semi-empirical, – Conceptual physically based.

3.2.1 Empirical USBR Approaches

USBR (1988) gave semi-quantitative criteria indicating certain hazard ranks (e.g., high and low danger zones) as a function of water depth and ﬂow velocity. Given the lack of experimental data, the rankings in USBR (1988) were mainly based on expert judgements of the authors. In general, three different charts summarize, respectively for: – Passenger vehicles (Fig. 3.1a), – Adults (Fig. 3.1b), – Children (Fig. 3.1c). The danger level as a function of water depth and velocity, to identify at least approximately: – High danger zone, – Judgement zone (where the judgment is essentially very subjective), – Low danger zone.

3.2.2 Semi-empirical Approach

The first systematic study on human stability in flooded areas was carried out at Colorado State University (CSU) at the end of the 1980s of the last century (Abt et al. 1989). The aim was to determine the joined threshold in terms of water depth and velocity, above which human life is at risk. Such a condition corresponds to the impossibility for an adult person to stand or to maneuver his/her movements in a flowing stream. In that study, the experimental tests were carried out by using 20 humans (2 females and 18 males) and a rigid monolith, put in a laboratory channel with a variable slope. The mass m of the human beings was between 41 and 91 kg and their height between 152 and 191 cm. The mass of the monolith, meant to represent the lower limit of the humans stability, was 53.4 kg and a height of 152 cm. In total, 71 tests were carried out, in particular 65 with the humans and 6 with the monolith. Moreover, two slope values (1.5 and 0.5%) with four different ground surface (grass, smooth cement, steel and gravel). All of the humans were dressed in the same way (jeans, slacks, sweater, tennis shoes, light boots) to collect reliable data. 3.2 Models of Human Beings Stability 27

Fig. 3.1 Depth-velocity ﬂood danger level relationship for passenger vehicles (USBR 1988). (a) Passenger vehicles, (b) adults, (c) children 28 3 Flood Impact on Human Beings Stability

To represent the threshold of human stability the multiplication U Á h has been adopted, where h is the water depth (in m) and U is the stream ﬂow (in m/s). The theoretical values for the monolith vary from about 0.14 m2/s to about 0.56 m2/s, according to the equation:

M ¼ ½ ðÞÁW À B c À ðÞP À 0:5h ð3:1Þ where M is the sum of the moments around the downstream edge of the monolith, W is its weight, C its thickness, B is the Buoyancy and P is the hydrodynamic force of the stream ﬂow. At the beginning of the tests, the value of U Á h was set at 0.56 m2/s for each test sample, that was then stressed by different combinations of the quantity U Á h until losing stability. For humans the threshold for the quantity U Á h was in a range between 0.70 and 1.94 m2/s for ground slope equal to 1.5%. When the test channel decreased to 0.5% the threshold values then increased to a range between 0.93 and 2.13 m2/s. Those values were by far higher in comparison to those obtained by means of the monolith, because of the instinctive natural ability of humans to compensate their posture to adapt to the changing solicitations due to the stream ﬂow and also to the adherence of the ground surface. In general, the threshold values of the quantity U Á h came out to be higher for tall, heavy humans in comparison to smaller, lighter people. In the case of the monolith, the values of the threshold for the quantity U Á h in the range between 0.22 and 0.39 m2/s for slope equal to 1.5% (Fig. 3.2).

1.4 2.5

1.2 2.0 1.0

1.5

0.8 /s) 2 (m 0.6

vd 1.0 flow depth [m]

0.4 0.5 0.2 Product number PN velocity times depth

0.0 0.0 0 12 34 0 100 200 flow velocity [m/s] height times mass hm [m kg]

human subjectsmonolith human subjects monolith

Fig. 3.2 Conditions of incipient losing stability for humans in a stream ﬂow (Abt et al. 1989) 3.2 Models of Human Beings Stability 29

Water Depth - Velocity Chart Lower Envelope Experiments from Abt et al. (1989)

2.00 Just Humans

Including Monolith 1.50 if = 1.5%: Uh = 0.7 m²/s

if = 0.5%: Uh = 0.93 m²/s 1.00

0.50 Water Depth (m) Water

0.00 012345 Velocity (m/s)

Fig. 3.3 Lower envelope of the experimental results about the incipient conditions of losing stability on the basis of the experimental data of Abt et al. (1989)

Because of the procedure adopted during the tests, the results may not be completely representative of the real stress conditions during a flood event. So Abt et al. (1989) indicates the following limitations: • Each single human was influenced by the availability of safety equipment, • Each single human was progressively learning how to make proper manoeuvres during the tests • The tests session, sometimes lasting 2 h and including three or four tests, may have made the participants tired, • Test conditions were optimal, characterized by good lighting and warm water with a temperature between 20 and 26 C, in a clear stream, without bottom and floating transport, • The people tested, were between 19 and 54 years old, and were all in good health, • No additional loads for the people tested. The lower envelope of the experimental results of Abt et al. (1989) is reported in Fig. 3.3, for both the tests on the humans and the whole set of tests, including those carried out on the monolith. 30 3 Flood Impact on Human Beings Stability

Table 3.1 People under test at the Helsinki University of Technology (Maijala 2001) Sex Age (years) Height (m) Mass (kg) Height Â mass (m Â kg) 1 Male 28 1.70 69 117 2 Male 31 1.95 100 195 3 Male 28 1.79 76 136 4 Female 32 1.62 57 92 5 Male 60 1.82 94 171 6 Female 17 1.60 48 77 7 Male 19 1.74 71 124

3.2.3 Laboratory Tests at Helsinki University of Technology

In the framework of the European Project RESCDAM (Development of Rescue Actions Based on Dam-Break Flood Analysis, 1999–2001) some additional tests have been carried out concerning the stability of the humans in flooding conditions, again considering as survival index the quantity U Á h (Maijala 2001). The experiments have been carried out at the Ship Laboratory at Helsinki University of Technology (HUT), in a test pool 130 m long, 11 m wide, about 5.5 m deep, which allowed to obtain up to 8 m/s of flow velocity, with cold water at about 16 C. (To this aim), a specific platform had been set up to place the people being tested. In particular, there were seven participants (five males and two females), with a height between 160 and 195 cm, a mass between 48 and 100 kg, aged between 17 and 69 years old (Table 3.1). Participants number 1 and number 2 were professionals from rescue teams. All of them were dressed with a Gore-Tex survival suit and Safety helmet (Fig. 3.4), while participant number 3 was also equipped with waders (Fig. 3.5). All of them were linked to a safety rope and there was also a banister that they could clutch just before losing stability, and in that moment a second safety rope come into operation. Each participant (was tried for different water depths) and, before each experi- ment, was taught about the safety procedures in still water. The initial values of h and U were set in order to make the quantity U Á h low enough to guarantee good stability and the possibility of a ford. The participants were asked to walk through the flow, both in the flow direction and perpendicularly and countercurrent. If the participant was able to maintain his/her ability to maneuver, the velocity was gradually increased, until losing stability or maneuverability (Figs. 3.6 and 3.7). Finally, the critical values of h and U were recorded, along with interviewing the participant about his/her impressions. Such procedures had been followed by all of the seven participants, and each one of them performed four tests. During the tests, the velocities were between 0.6 and 2.75 m/s and the water depths were between 0.3 and 1.1 m. Because of the remarkable differences among the performances of the different participants, the critical values of the quantity U Á h came out to be extremely variable: in fact the range of the results was between 0.64 and 1.26 m2/s, with a better resistance (that is larger values of U Á h) by the tallest and heaviest participants (Figs. 3.8 and 3.9). 3.2 Models of Human Beings Stability 31

Fig. 3.4 Participant n.4 (Maijala 2001)

3.2.4 Comparison of Results and Envelope Threshold

The critical values of the quantity U Á h resulting from the two considered experiments are reported in Fig. 3.10 as a function of the characteristics of the humans participating in the tests, represented by the quantity a Á m where a is the height and m is the mass of the selected participant. It is important to note that the threshold values obtained by HUT (RESCDAM project) are far lower in comparison to those obtained by CSU. The differences can be explained due to the different clothing and ground surface. In particular, the participants dressed in a survival suit in the HUT tests, instead of normal dress like in the CSU tests. The survival suit tends to trap air bubbles, increasing the ﬂoating capacity of the participant; moreover, the cross section offered by a participant dressed in survival suit is larger in comparison to a participant dressed in just jeans and a T-shirt: this generates a higher hydrodynamic force against the participant, making it more difﬁcult for him to maintain stability and maneuverability. In the HUT tests, the ground surface was more slippery in 32 3 Flood Impact on Human Beings Stability

Fig. 3.5 Participant n.3 (Maijala 2001)

Fig. 3.6 Participant n.1: h ¼ 1.1 m and U ¼ 0.7 m/s (Maijala 2001) 3.2 Models of Human Beings Stability 33

Fig. 3.7 Participant n.5: h ¼ 1.07 m and U ¼ 1.0 m/s (Maijala 2001)

Fig. 3.8 Results of the tests in (h, U) chart and critical values of the quantity U Á h (Maijala 2001) comparison to the CSU tests, obviously with a higher destabilizing effect on the tested people. Definitively, the results obtained by CSU tests represent a condition of stability limit for people (sunk) by a flooding flow, while those obtained by HUT tests described a more realistic situation occurring in catastrophic hydrologic events. 34 3 Flood Impact on Human Beings Stability

Fig. 3.9 Results of the tests in (heightÁmass, U) chart (Maijala 2001)

Fig. 3.10 Comparison of the results for the stability tests carried out by HUT and CSU in (am, Uh) chart, including the values representing the monolith case (Maijala 2001)

(Indeed, in real conditions). The effective critical values of the quantity U Á h are lower than the above mentioned survival limits, as the water could be much colder and more turbid, more limited visibility, ﬂoating and bottom sediment transport could hurt (sunk) people and the ground surface could be very slippery. According to these considerations, realistic values to estimate the stability threshold for humans could be given by the following formulas:

U Á h ¼ 0:006am þ 0:3, for adults and good adherence, U Á h ¼ 0:002am þ 0:1, for adults and bad adherence, where U is expressed in m/s, h in m, a in m and m in kg (Fig. 3.11). 3.2 Models of Human Beings Stability 35

Fig. 3.11 Stability threshold for humans as a function of the characteristic of the (sunk) people

The results look quite similar on a (U, h) chart, as the lower envelope for humans is respectively U Á h ¼ 0.70 and U Á h ¼ 0.64, as shown in Fig. 3.12. Therefore, a threshold equal to U Á h ¼ 0.6 m2/s could be taken as a reference in terms of the standard limit for the stability of humans in a ﬂooded area. By the way, such an approach has been adopted also by the administration of the French city of Toulouse. In facts, its PPRI (Plan de Prévention du Risque d’Inondation, that is “inundation risk prevention plan”) refers to a similar pattern, as reported in the following Fig. 3.13 (http://www.toulouse-inondation.org/page-300/le-risque.html).

3.2.5 Conceptual Physically-Based Approaches

In the last 20 years, a number a studies have approached the problem of the human instability in ﬂood ﬂows from a conceptual point of view, that is considering the threshold conditions of the equilibrium expressed in terms of the physical forces to which a human body or an object are subject to. 36 3 Flood Impact on Human Beings Stability

Water Depth - Velocity Chart Human Stability

CSU (Abt et al., 1989) 1.00 HUT (Maijala et al., 2001) Uh = 0.6 m²/s Monolith (Abt et al., 1989)

field of experimental data set 0.50 Water Depth (m) Depth Water

0.00 012345 Velocity (m/s)

Fig. 3.12 Stability threshold for human beings

Fig. 3.13 Stability threshold for human beings according to the French city of Toulouse PPRI (Plan de Prévention du Risque d’Inondation, that is “inundation risk prevention plan”), http://www. toulouse-inondation.org/page-300/le-risque.html

Jonkman and Penning-Rowsell (2008) reported that, essentially, two different hydrodynamic mechanisms can cause instability in flood flows: moment instability (toppling) and friction instability (sliding), as shown for example in Fig. 3.14a, b, rearranged from Xia et al. (2014). From simplified schemes of the mechanisms, they showed that the often-used depth-velocity (hv) product has a physical relationship with 3.2 Models of Human Beings Stability 37

Fig. 3.14 The two different hydrodynamic mechanisms can cause instability in flood flows: (a) moment instability (toppling) and (b) friction instability (sliding), rearranged from Xia et al. (2014) moment instability whereas friction instability is more closely related to the hv2 product. The results of new full-scale experiments by the FHRC have been reported. These new results, covering circumstances very closely resembling urban flash flooding, show that low depth/high velocity flood waters are more dangerous than suggested by Abt et al. (1989). This seems to be due to the effects of friction instability, which appears to occur earlier than moment instability for the combinations of shallow depth and high velocities. However, they also recognized that the benefit of more refined schematization could be limited, as other phenomena affect human stability in flows (as already remarked by Karvonen et al. 2000): – Bottom characteristics, for instance evenness and obstacles. – More water characteristics, for instance water temperature, ice, other debris, or even animals (e.g., fish, snakes, alligators) which could cause people to react in a manner other than seeking maximum stability (e.g., by swimming away). – Human vulnerability factors. Additional loads such as clothing, disabilities, age, fatigue, and hypothermia would reduce ability to lean into the flow. In particular, the tests completed so far with people used healthy adults. Children and the elderly are likely to be particularly vulnerable to instability in flowing water. In flood situations, such as those which happen in the middle of the night, tiredness, disorientation, and mental stress could be significant factors too. – Physical conditions. Lighting and visibility, wind, waves, and flow unevenness which suddenly changes water velocity and depth (Figs. 3.15, 3.16 and 3.17). Xia et al. (2014), following the same issue, but in a more detailed way, about the mechanical interpretation of the human instability. 38 3 Flood Impact on Human Beings Stability

a b person person

Fperson L Fperson

F F flow h flow h Fbuoy v Fbuoy v F  friction d P 2 d1

Fig. 3.15 Models of the human body for moment (a) and for friction (b) instability. Symbols as in this figure: d1 is the distance from person’s pivot point (point P) to the centre of mass (m) (equals to cos(α)L); d2 is the distance from person’s pivot point (point P) to the centre of the vertical buoyancy force (m); Fbuoy is the vertical buoyancy force (N); Fflow is the horizontal force of the flow on an object (N); Ffriction is the friction force between a person and the stream bed (N); Fperson is the person’s weight (N); h is the water depth (m); L is the person’s height (m); P is the point in this figure around which a person pivots while leaning into the flow; υ is the water flow velocity (m/s); α is a person’s angle of tilt in flowing water (degrees)

Fig. 3.16 Theoretical boundaries for moment and friction instability (the following input variables 2 have been used: m ¼ 75 kg; g ¼ 9.81 m/s ; α ¼ 75 ; L ¼ 1.75 m; CD ¼ 1.1; B ¼ 0.4 m; μ ¼ 0.5; ρ ¼ 1000 kg/m3)

They checked their theory by means of a significant database of more than 50 experimental tests on the stability of a human body conducted in a flume using a scaled model body, with the incipient velocities being measured for a range of different water depths (Fig. 3.18). Their work substantially confirmed the following key conclusions, already found out by Jonkman and Penning-Rowsell (2008). – Sliding instability mainly occurs for shallow depths and high velocities, with the critical condition being that the drag force induced by the flow is governed by the frictional force between the soles of the feet and the ground surface. 3.2 Models of Human Beings Stability 39

Fig. 3.17 Depth-velocity product as a function of the mass of a human body for the RESCDAM experimental data (Karvonen et al. 2000) with best-ﬁtting trend line

Fig. 3.18 Two standing postures of the model human body in the ﬂume: (a) facing and (b) with the back towards the oncoming ﬂow

– In contrast, toppling instability of the body mainly occurs for higher depths and lower velocities, with the critical condition being the driving moment. This moment is governed by equating the product of the drag force and lever arm from the bed to the centre of mass, with the resisting moment, which is determined by the product of the effective weight of the body and the offset lever arm from the centre of mass to the pivot point. 40 3 Flood Impact on Human Beings Stability

Fig. 3.19 Suggested stability thresholds for (a) children and (b) adults, after Xia et al. (2014)

Moreover, based on the theory developed by Xia et al. (2014), and similar to the incipient motion for a coarse sediment particle, some equations (not reported here) were derived for the incipient velocity of a human body for the instability modes of respectively sliding and toppling. But, for practical purposes, it is very interesting that Xia et al. (2014) suggested different stability thresholds for adults and for children, as reported in Fig. 3.19 for the case of sliding stability. In particular, it can also be observed that, for the adults, the thresholds proposed by Xia et al. (2014) on the basis of the experiments they carried out on their puppets (bold lines in Fig. 3.19) look quite more conservative in comparison to the experimental data obtained by real humans and analyzed by other Authors (thin lines in Fig. 3.19). Milanesi et al. (2015) proposed a model which provides a physically based and quantitative description of the vulnerability related to slipping, toppling, and drowning of a human body in the flow field, keeping into account, in an explicit way, not only the local slope and the friction coefficient of the soil but even the density of the water, that may become a significant parameter in case the human beings are threatened by a debris flow. Such a model brought to the define instability thresholds like those reported in Figs. 3.20, 3.21, 3.22 and 3.23. 3.2 Models of Human Beings Stability 41

Fig. 3.20 Stability thresholds for adults (thin line) and children (thick line), found out by Milanesi et al. (2015): (a) slipping, (b) toppling, and (c) drowning. Ya and Yc represent, respectively, the height of the adults and the height of the children (adult: 1.71 m and 71 kg; children: 1.21 m and 22.4 kg). (d) is their combination. (e) The experimental data from the literature and the thresholds by Xia et al. (2014) for both adults and children (dashed lines). High, medium, and low vulnerability areas are, respectively, identiﬁed by red, orange, and yellow colors. Here ρ ¼ 1000 kg m–3 and ϑ ¼ 0∘

1.5

(m) 1 h

0. 0.5 30 0.46 0.60

0 01 234 U (m s–1)

Fig. 3.21 Sensitivity analysis of the stability curve to the variation of the friction coefﬁcient μ in case of adult person, clear water (ρ ¼ 1000 kg m–3), and horizontal terrian ϑ ¼ 0∘), from Milanesi et al. (2015) 42 3 Flood Impact on Human Beings Stability

b a 2 2 c 2 =1000 kg m–3,s=0% =1400 kg m–3,s=0% 1.5 1.5 1.5 =1000 kg m–3,s=15% =1400 kg m–3,s=15%

1 1 1 (m) (m) (m) h h h

0.5 0 0.5 1000 0.5 30 1600

0 0 0 01 23 4 01 23 4 01 23 4 U (m s–1) U (m s–1) U (m s–1)

Fig. 3.22 The effect of (a) slope and (b) density on the stability threshold derived for an adult person (Milanesi et al. 2015). The effect of slope (a) is studied for clear water (ρ ¼ 1000 kg m–3) while the role of density (b) is tested for the case of horizontal terrain. The labels indicates the slope value s (%) and ρ (kg m–3) associated to the curves. The intermediate curves are deﬁned for values of s spaced of 6% and ρ spaced of 200 kg m–3. The dot in the lower right corner in (a) is representative for the situation of Fig. 3.23. The synergic effect of density and slope with characteristic values of hyperconcentrated ﬂows in alpine areas (in this case, ρ ¼ 1400 kg m–3, that corresponds to a mass concentration of 24%) can be observed in (c)

Fig. 3.23 Slipping instability and dragging of a woman washed away by shallow ﬂood waters on a sloping terrain. (Source http://www.youtube.com/wath?v¼YAv_yUsAvgc. Last access 22 September 2014)

References

Abt SR, Wittler RJ, Taylor A, Love DJ (1989) Human stability in a high flood hazard zone. Water Resour Bull 25(4):881–890 Federal Emergency Management Agency (FEMA) (1979) The floodway: a guide for community permit officials. US Federal Insurance Administration, Community Assistance Series, No. 4 Jonkman SN, Penning-Rowsell E (2008) Human instability in flood flows. J Am Water Resour Assoc (JAWRA) 44(4):1–11. https://doi.org/10.1111/j.1752-1688.2008.00217.x Karvonen RA, Hepojoki A, Huhta HK, Louhio A (2000) The use of physical models in dam-break analysis. RESCDAM final report. Helsinki University of Technology, Helsinki Maijala T (2001) RESCDAM: development of rescue actions based on dam-break flood analysis. Final report, grant agreement no. Subv 99/52623 Community Action Programme in the field of civil protection. Finnish Environment Institute, Helsinki Milanesi L, Pilotti M, Ranzi R (2015) A conceptual model of people’s vulnerability to floods. Water Resour Res 51:182–197. https://doi.org/10.1002/2014WR016172 References 43

Roberts CPR, Alexander WJR (1982) Lessons learned from the 1981 Laingsburg flood. Civ Eng South Africa 24(1):17–27 USBR – United States Bureau of Reclamation (1988) Downstream hazard classification guidelines. ACER Technical Memorandum No. 11, Assistant Commissioner – Engineering and Research, Denver, December Xia J, Falconer RA, Wang Y, Xiao X (2014) New criterion for the stability of a human body in floodwaters. J Hydraul Res 52(1):93–104. https://doi.org/10.1080/00221686.2013.875073 Chapter 4 Flood Impact on Mobilizable Objects

Inundation phenomena tend to mobilize the objects located in the flooded areas. So, the relative risk of an inundation must be evaluated taking into account this effect, most of all with regarding all of the vehicles parked in the flood area (Figs. 4.1 and 4.2). Although proper alert procedures should reduce this factor of risk, by ordering an evacuation before the flooding event, it is important to assess the stability threshold for vehicles. There is still a lack of specific studies in this field. Nevertheless, it can be broadly estimated that an average car with a weight of 100000 N, a length of 420 cm and a width of 170 cm, starts to float in still waters when the water depth reaches 50 Ä 60 cm, depending on the characteristics of the vehicle, as the (cockpit) sealing is usually quite poor. The results of some laboratory experiments carried out by Cacioli Paciscopi (1999) at Florence University, with scale models sunk in a stream flow, have also been considered by the administration of Liguria Region in Italy (Fig. 4.3). These results can be enveloped by the expression reported in Fig. 4.4. Vehicle-related deaths comprise more than half of all flash flood fatalities in the United States. Using the publication Storm Data from the United States National Climatic Data Center, Keller and Schmidlin (2012) found 555 vehicle-related flood deaths that occurred in 355 flooding events during 1995–2005. Males accounted for 60% of the deaths. The difference in death rates between the sexes was small at ages 19 and younger but males died at twice the rate of females for ages 40 and older. Elevated deaths rates were found for both males and females under age 5 and over 60. Flooding events classified as flash floods accounted for most of the fatalities.

Fig. 4.1 Cars and rubbish containers during a ﬂood event (Genova, Italy, 2011)

Fig. 4.2 Cars, motorcycles and rubbish containers during a ﬂood event (Genova, Italy, 2011) 4 Flood Impact on Mobilizable Objects 47

Fig. 4.3 Experiments at scale model carried out at Florence University (Cacioli Paciscopi 1999)

Water Depth - Velocity Chart Mobilization of Vehicles

h = 0.65 - 0.18U

1.00 field of experimental data set experimental values

0.50 Water Depth (m) Water

0.00 012345 Velocity (m/s)

Fig. 4.4 Envelope of the stability threshold for vehicles 48 4 Flood Impact on Mobilizable Objects

References

Cacioli Paciscopi G (1999) L'asportazione idrodinamica degli autoveicoli in sosta nelle inondazioni urbane. Tesi di Dottorato di Ricerca in Ingegneria Idraulica. Università degli Studi di Firenze Keller D, Schmidlin T (2012) Vehicle-related ﬂood deaths in the United States, 1995–2005. J Flood Risk Manage 5:153–163 Chapter 5 Global Criteria for Impact Estimation

5.1 Introduction

In order to take into account the multiple factors examined in the previous paragraphs (structural safety of buildings, stability of humans, mobilization of vehicles), a number of empirical criteria have been deﬁned in literature, about the global level of risk in ﬂoodable areas.

5.2 New South Wales (Australia) Criteria

According to Smith (1989), the flooding streamflows with a velocity higher than 2 m/s are dangerous from the point of view of a buildings safety. This consideration has been assumed, for example, by the guidelines for the development of the floodable plans of New Wales in Australia (Fig. 5.1). To define the thresholds of respectively low and high relative risk in the range of the velocities below 2 m/s, some factors are taken into account explicitly, like the safety of the residents during an emergency evacuation (NSW Government 1986, from: Smith 1991).

5.3 ESCAP Criteria

Very similar to the previous one, the criteria proposed by the Economic and Social Commission for Asia and the Paciﬁc of the United Nations (UNESCAP) in its Manual and Guidelines for Comprehensive Flood Loss Protection and Management (1991) considers the identiﬁcation of low and high risk through linear functions that link the values assumed to be critical in terms of water depth and velocity. Unlike the previous one, the lower threshold (low risk) for still waters is set equal to 0.80 m

Water Depth - Velocity Chart New South Wales, Australia (1986) 2.00

high risk

1.00 Water Depth (m) Water low risk 0.00 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Velocity (m/s)

Fig. 5.1 Categories of relative risk for buildings safety, including factors linked to the safety of the residents during emergency evacuation (NSW Government 1986, from: Smith 1991)

Water Depth - Velocity Chart

2.00 ESCAP (1991)

high risk

1.00 Water Depth (m) Water low risk 0.00 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Velocity (m/s)

Fig. 5.2 Relative risk threshold according to ESCAP (1991) instead of 0.70 m. Such criterion, which is a review of the previous one, is reported in Fig. 5.2.

5.4 CEDEX (Spain) Criteria

A different proposal about the individuation of ﬂoodable areas, but with a low relative risk, was introduced in Spain by CEDEX (Centro de Estudios Hidrograﬁcos) in the early 1990s (Témez 1992; Marco 1994). It is based again on a combined criterion about water depth and velocity with U Á h ¼ 0.5 m2/s for values of U and 5.5 Indications of Po River Catchment Authority (Italy) 51

Water Depth - Velocity Chart (Témez 1992) 2.00

1.00 Water Depth (m) Water

0.00 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Velocity (m/s)

Fig. 5.3 Thresholds of relative risk according to Témez (1992) h lower than the reference critical thresholds, which are assumed empirically taking into account both the multiple real situations and the uncertainties in the evaluation of the maps of the ﬂoodable areas. So, CEDEX assumes 1 m and 1 m/s as threshold values for respectively water depth and velocity. Such a criterion is reported in Fig. 5.3.

5.5 Indications of Po River Catchment Authority (Italy)

Already in 2001, the Italian Autorità di Bacino del Fiume Po (Po River Catchment Authority) reported an indication about the hydraulic compatibility of proposal of use of areas exposed to hydrologic-hydraulic risk, to be assessed on the basis of two conditions: (a) the settlements or the structures in the floodable areas are not exposed to any risk, and (b) the soil occupancy does not create an obstacle for the runoff. To check that neither the settlements nor the structures are risk exposed, it must be taken into account that: • Structures must be considered risk exposed depending on the conditions of water depth and velocity on the ground; for example, if the threshold conditions defined by Fig. 5.4 in terms of water depth h (m) and flow velocity U (m/s), on the riverside of the considered area; • If the hydraulic computations do not allow estimating the velocity values in the different parts of the cross sections, the chart of Fig. 5.4 must be intended with reference to the mean velocity in the cross section.1

1It is meant that the so deﬁned hydraulic conditions remain more or less unvaried across the section. 52 5 Global Criteria for Impact Estimation

Risk Level in Floodable Areas 2.0 1: Not Compatible with Urbanization 1.5 2: Urbanization not advisable 1.0 , in m h 2: Urbanization 0.5 with measures 4 0.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 U, in m/s

Fig. 5.4 Criteria for the evaluation of the relative risk level (from the website of the Po River Catchment Authority, Parma, 2001)

• It is possible to distinguish at least four different conditions in terms of risk level: 1. Areas at risk (and) not compatible with any kind of urbanization; in this case the infrastructures must be evaluated looking at the interferences with the hydrodynamic patterns of the stream; 2. Areas that may be occupied exclusively by public (or of public interest) infrastructures that cannot be located elsewhere and are prepared to resist the solicitations of an inundation; 3. Areas that can be urbanized with constructive shrewdness, to avoid damages to structures and goods and/or making an immediate evacuation of people and goods away from the ﬂoodable area easier; 4. Floodable areas with risk levels that are acceptable also for minors and the disabled with (accompaniment).

Such a proposal, that is still at a preliminary level, is not yet part of any norm (Rosso 2002).

5.6 FEMA (USA) Criteria

The Federal Emergency Management Agency (FEMA 1997) of the United States contemplates the classification of the floodable areas into three main classes: • Special Flood Hazard Areas: floodable areas with a return period of 100 years. • Moderate Flood Hazard Areas: floodable areas with a return period of 500 years, with the exclusion of Special Flood Hazard Areas, that are floodable areas with a return period of 100 years with a water depth lower than 1 ft (that is about 30 cm), areas with a drained surface lower than 1 mile2 (that is about 2.5 km2) and areas 5.6 FEMA (USA) Criteria 53

protected by flooding with a return period of 100 years by means of embankments. • Minimal Flood Hazard Areas: areas which are external to the floodable area with a return period of 500 years. The mapping of the flooding risks established by the Federal Emergency Man- agement Agency (FEMA 1979, 2002) of the United States in the framework of the preparation of the Flood Insurance Rate Maps (FIRMs) to create Flood Insurance Studies (FIS), distinguishes the following zones. • Floodway,defined as the stream bed and the floodplain that must be reserved to the flood transit, in order to drain the peak flow with 100 years of return period without increasing the peak water depth of more than a selected value, that is usually equal to 1 foot (about 30 cm). • Zone A. Areas flooded by an event with a return period of 100 years, where the water depth has not been estimated by means of numerical hydraulic models but by means of empirical relationship like depth-frequency, slope-conveyance, signs of events with about 100 years of return period (Cobb 1985). In these areas, the water depth is not indicated explicitly. • Zone AE. Areas flooded with a return period of 100 years, where the water depth has been estimated by means of numerical hydraulic models and is indicated explicitly. • Zone AH. Areas flooded by an event with a return period of 100 years, where the water depth is estimated by means of numerical hydraulic models at a value between 1 foot and 3 feet (that is between 30 and 90 cm). In these areas, the average water depth is indicated explicitly. Usually, for the detailed modelling of the zones AH, three classes are contemplated; they correspond to a water depth respectively lower than 1 foot (about 30 cm), 2 feet (about 60 cm) and lower than 3 feet (about 90 cm). • Zone A99. Areas classified as Special Flood Hazard Areas under the protection of the Federal Emergency Management Agency, where the building and the urban order have reached a safety level inspected by FEMA itself. In these areas the average water depth is indicated explicitly. • Zone AR. Areas classified as Special Flood Hazard Areas and already protected by structural protection systems with a return period of 100 years which are going to be restored. • Zone V. Areas flooded by an event with a return period of 100 years, with an additional risk related to tidal phenomena, where the water depth has been evaluated by means of approximated methods. • Zone VE. Areas flooded by an event with a return period of 100 years, with an additional risk related to tidal phenomena, where the water depth has been estimated by means of numerical hydraulic models and is indicated explicitly. • Zone X. Areas flooded by an event with a return period of 500 years which are excluded by the Special Flood Hazard Areas, areas flooded by an event with a 54 5 Global Criteria for Impact Estimation

return period of 100 years where the water depth is less than 1 foot (about 30 cm), areas with a drained surface lower than 1 mile2 (about 2.5 km2) and areas protected by an event with a return period of 100 years by embankment systems. In these areas the water depth is not indicated explicitly. • Zone D. Areas which can be flooded but with an undetermined level of risk because of the lack of specific studies, not used for any FIS with a return period of 500 years which are excluded by the Special Flood Hazard Areas, areas flooded by an event with a return period of 100 years where the water depth is less than 1 foot (about 30 cm), areas with a drained surface lower than 1mile2 (about 2.5 km2) and areas protected by an event with a return period of 100 years by embankment systems. In these areas the water depth is not indicated explicitly. It must be noted that FEMA (2002) established that water depth mapping must be carried out defining classes with an approximation of 30 cm (1 foot). (To the aims of a detailed hydraulic modelling), topographic maps and digital terrain models assume a resolution of the contour lines of 4 feet (about 120 cm) that must be doubled to 2 feet (about 60 cm) in plain areas. Moreover, the topographic data must be updated, by means of spot field surveys.

5.7 Comparison of Different Approaches

The criteria described so far show a large range of solutions. They depend on the kind of relative risk that is considered, usually in terms of instability (for buildings, people and vehicles). Also, take into account implicitly all of the complicated factors, often not explicitable by means of physical and mathematical models, that intervene during a ﬂooding event and, sometimes, of the uncertainties in the mapping processes concerning the ﬂoodable areas. An overview of the examined criteria is reported in Fig. 5.5. To comment on these results it can be observed that: • The relative risk thresholds in terms of the relationship h versus U usually have a shape that looks decreasing monotonically h ¼ h(U), which means that when the velocity increases then the water depth decreases; • About the stability of the humans, the empirical relationships h ¼ h(U) are of hyperbolic shape, with U Á h ¼ constant, like the one about structural safety, while the thresholds of a global kind are often drawn empirically with a linear shape, sometimes even dashed, to take into account the different causes of the risk; • The thresholds evaluated in terms of moments of the loads (Black 1975) show a pseudo-exponential shape; 5.7 Comparison of Different Approaches 55

Water Depth - Velocity Thresholds of Relative Risk

ESCAP (1991) High & NSW (1986) High ESCAP (1991) Low 2.00 NSW (1986) Low Témez (1992) Human Stability (Abt et al., 1989; Maijala, 2001) Monolith (Abt et al., 1989) Mobilization of Vehicles (University of Florence) Structural Safety for Wooden Buildings 1.50

high risk

1.00 FEMA AO3-:-AH3 (3 ft)

Water Depth (m) FEMA AO2-:-AH2 (3 ft)

0.50

FEMA AO1-:-AH1 (1 ft) low risk

0.00 0.0 1.0 2.0 3.0 Velocity (m/s)

Fig. 5.5 Comparison of the global criteria of relative risk and thresholds for: the stability of human beings, the mobilization of vehicles, the structural safety of wooden buildings

• To determine the thresholds of the stability of the humans, ground slope is quite important, as the experimental test shows that such a threshold tends to decrease when the slope is increasing; • Considering both the difficulties in obtaining significant and reliable values of the flow velocity and the influence of the storage phenomena, the Federal Emergency Management Agency of the United States defines the risk thresholds just in terms of classes of water depth, with an approximation of 30 cm (1 foot) (FEMA 2002). 56 5 Global Criteria for Impact Estimation

References

Autorità di Bacino del Fiume Po (Po River Catchment Authority) (2001) Direttiva sulla piena di progetto da assumere per le progettazioni e le verifiche di compatibilità idraulica. Direttiva n. 18 del 26 aprile 2001. Parma, Italy Black RD (1975) Flood proofing rural residences. A Project Agnes Report, Pennsylvania New York State College of Agriculture and Life Sciences, Ithaca. Prepared for Economic Development Administration, Washington, DC, Office of Technical Assistance Cobb ED (1985) Evaluation of streams in selected communities for the application of limited detail study methods for flood-insurance studies. US Geological Survey Water Resources Investiga- tions 85-4098 Economic and Social Commission for Asia and the Pacific of the United Nations (UNESCAP) (1991) Manual and guidelines for comprehensive flood loss protection and management Federal Emergency Management Agency (FEMA) (1979) The floodway: a guide for community permit officials. US Federal Insurance Administration, Community Assistance Series, No. 4 Federal Emergency Management Agency (FEMA) (1997) FEMA’s multi-hazard identification and risk assessment (MHIRA) – Subpart C: Hydrologic Hazards, 1st January Federal Emergency Management Agency (FEMA) (2002) Guidelines and specifications for flood hazard mapping partners, February Marco JB (1994) Flood risk mapping. In: Rossi G, Harmancioğlu N, Yevjevich V (eds) Coping with floods, NATO ASI series (series E: applied sciences), vol 257. Springer, Dordrecht New South Wales (NSW) Government (1986) Floodplain development manual. Australia Rosso R (2002) Manuale di protezione idraulica del territorio: prima edizione. CUSL, Milano, Italy Smith DI (1989) A dam disaster waiting to break. New Scientist, 11th November. pp 42–46 Smith DI (1991) Extreme floods and dam failure inundation implications for loss assessment. In: Proceedings of a Seminar “Natural and Technological Hazards: Implications for the Insurance Industry”. University of New England, Armidale, NSW, pp 149–165 Témez JR (1992) Control del desarrollo urbano en las zonas inundables. CICCP monographs. Madrid, Spain Chapter 6 Hydrodynamic Criteria for Impact Evaluation

6.1 Introduction

To define norms about floodable areas as a function of the most significant quantities, especially concerning the amount of the water depths and of the flow velocities, it is appropriate, on the basis of the state-of-the-art, to introduce an analytical criterion, although related to a simplified physical scheme, to express the risk in a quantitative way. The analysis of Black (1975) has demonstrated that it is possible to deal with the problem in an analytical way in the case of the buildings, but it has also demonstrated that the solution largely depends on the characteristics of the buildings. The implementation of a specific analytical criterion (linked to the kind of buildings) is not appropriate to set up a planning criteria. Despite some drastic simplifications, referring to a physical scheme it is useful to understand the phenomena and to provide general indications, to define an official criterion of relative risk. In this chapter, it is considered a mechanical solicitation of a stream in terms of force and energy. It is shown that such a criterion can be calibrated in an appropriate way in order to represent the different kinds of situations reported by the experimental data. Then the implementation is also discussed as it is necessary to prepare recommendations to integrate the general criteria for the catchment planning. This approach is developed referring to the determination of the areas with different relative risk inside inundation bands individuated in the framework of the already approved norms.

6.2 Hydrodynamic Thresholds

As a simplified geometric scheme, a vertical wall can be adopted, indefinitively large, orthogonally hit by a uniform flow characterised by a water depth h and a velocity U, assessing the unitary horizontal force (per unit of width) against the wall,

© Springer Nature Switzerland AG 2019 57 D. F. Bignami et al., Flood Proofing in Urban Areas, https://doi.org/10.1007/978-3-030-05934-7_6 58 6 Hydrodynamic Criteria for Impact Evaluation that is assumed to be perfectly sealed and not subject to any buoyancy effect. Since such a force is actually a physical quantity that can be measured, it means that it is something familiar to civil engineers. So, the amount of unitary force (per unit of width of the wall) is given by the expression: 1 1 S ¼ ρqU þ γh h ¼ ρhU2 þ γh2, ð6:1Þ 2 2 where ρ is the density of the streamflow, γ its specific weight, q the flow rate per unit of width of the streamflow, U is the velocity of the streamflow and h the related water depth. If h is in m, U in m/s, ρ in kg and γ in N/m3, then the unitary force S is expressed in N/m. It can be observed that, in still waters, the force is just equal to the hydrostatic one, that is ½ γ Á h. In case of moving water, there is the dynamic component ρ Á h Á U2, which increases quickly when U increases. For a given value of the force which can be tolerated by the system, the pairs of values h and U satisfying Eq. (6.1) create a monotonically decreasing function. This indicates that the dynamic component is more and more important when the velocity increases. That is the reason why the system can tolerate progressively lower values of the water depth when the flow velocity increases. Such a behaviour can be analysed in detail in the solving Eq. (6.1) respect to h for a given value of the total force S. In this way it is possible to obtain the curves h ¼ hS(V) reported in Fig. 6.1, which indicates, for a given total force S, when the velocity increases then the tolerable water depth decreases. They provide an analytical threshold for the relative risk under the assumption that the relative risk must be referred to the tolerable force. Another fundamental physical quantity which characterises the behaviour of the system is the specific energy, that is the total head, of the stream. For free surface waters, the total head is the sum of the water depth and the kinetic head:

U2 E ¼ h þ , ð6:2Þ 2g where g is the gravity acceleration. If h is in m, U in m/s and g in m/s2, then the total head E is expressed in m. Solving Eq. (6.1) respect to h for a given total head E and choosing the reference value of E equal to the one corresponding to the unitary total force S in static 1/2 conditions, that is E0 ¼ (2S/γ) , it is possible to obtain the two curves h ¼ hE(U) reported in Fig. 6.1. It can be seen that the water depth is higher or at least equal to hS(U) until the stream remains below a certain velocity. In these conditions, the total head remains below (2S/γ)1/2, that is the total head in static conditions (still water). However, when the velocity becomes higher than a certain value, which depends on S, the corresponding total head becomes higher than the reference static value. In this 6.2 Hydrodynamic Thresholds 59

Water Depth - Velocity for a Given Hydrodynamic Force, hS(U), & Constant Total Head, hE(U)

1.20 E0, m S, N/m 0.45 1000 1.00 0.55 1500 0.80 0.71 2500 1.01 5000 0.60

0.40

Water Depth (m) Water 0.20

0.00 012345 Velocity (m/s)

Fig. 6.1 Relationship between water depth and flow velocity for a given total hydrodynamic force with a constant total head case, the total head of the stream could assume values so high as to make the system unstable because of local dynamic phenomena (like wall scouring). So, it is better to associate the criterion of the allowable total head together with the criterion of the allowable total force. Therefore, choosing on the safe side of the relationship h ¼ h (U) ¼ min[hS(U), hE(U)] it is possible to obtain the curves reported in Fig. 6.2. The resulting threshold can be expressed analytically as: sffiffiffiffiffi! 1 U2 2S h ¼ hUðÞ; S : h ¼ min ρhU2 þ γh2 À S ¼ 0; h þ À ð6:3Þ h 2 2g γ and its value can be evaluated solving a simple optimization problem. The behaviour of the relationship which comes from this analytical formulation of the relative risk threshold, which will be named “hydrodynamic threshold” from now on, is compared in Fig. 6.3 with the empirical solutions of literature presented in the previous chapters (ESCAP 1991,NSW1986,Témez1992, Abt et al. 1989,Maijala 2001, Cacioli Paciscopi 1999). It can be seen that the conceptual approach, analytically expressed by Eq. (6.3) with a given value of S can represent in a reasonable way (by quite) different empirical indications, although those are different among them. For example, a total hydrodynamic force S equal to 1000 Ä 1500 N/m envelopes the lower threshold proposed by ESCAP (1991), while the corresponding higher threshold is approximated by a value equal to 2500 N/m. Both the empirical results proposed in literature on the basis of considerations about the stability of the humans and those coming from the envelope of the experimental study carried out concerning vehicles are approximated by a hydrodynamic threshold corresponding to 1500 N/m. The threshold 60 6 Hydrodynamic Criteria for Impact Evaluation

Water Depth - Velocity Chart h = Min [hS(U), hE(U)] Force (N/m) 1000 1.20 1500 1.00 2500 0.80 5000 0.60

0.40

Water Depth (m) Water 0.20

0.00 012345 Velocity (m/s)

Fig. 6.2 Relationship between water depth and stream velocity for a given total hydrodynamic force conditioned to the total head proposed by CEDEX (Témez 1992), although with a similar behaviour, looks like a representative of a cut-off approach linked to considerations which are independent from the hydrologic and hydraulic patterns of the system. Deﬁnitively, once it has been established the reference to be adopted for the tolerable total hydrodynamic force, the hydrodynamic approach offers a technically simple and physically based procedure to evaluate the thresholds of interest. Despite being founded on a very simple scheme, it considers physical quantities (total hydrodynamic force and total head) which can be measured in the ﬁeld or estimated by means of hydrologic and hydraulic models, also making the comprehension of the dynamic aspects of the phenomenon easier.

6.3 Implementation of Hydrodynamic Thresholds 6.3.1 Reference Values

The implementation of the hydrodynamic model requires the appropriate estimation of the tolerable total hydrodynamic force. Such a choice must be selected taking into account the characteristics, the structural resistance and the hydraulic seal of the elements (objects) at risk. On the basis of the experimental results and of the different prescriptions obtainable by literature, a value equal to 1500 N/m looks, for example, signiﬁcant of a low risk. Then, above 2500 N/m,ahigh risk condition arises. 6.3 Implementation of Hydrodynamic Thresholds 61

Water Depth - Velocity Chart Empirical and Hydrodynamic Thresholds of Relative

ESCAP (1991) High & NSW (1986) High ESCAP (1991) Low NSW (1986) Low 2.00 CEDEX (1992) Human Stability (Abt et al., 1989; Maijala, 2001) Monolite (Abt et al., 1989) Mobilization of vehicles (University of Florence) Structural Safety of Wooden Buildings 1.50 1000 N/m 1500 N/m 2500 N/m

high risk 1.00 FEMA AO3-:-AH3 (3 ft)

Water Depth (m) FEMA AO2-:-AH2 (3 ft)

0.50

FEMA AO1-:-AH1 (1 ft) low risk

0.00 0.0 1.0 2.0 3.0 Velocity (m/s)

Fig. 6.3 Comparison of the hydrodynamic thresholds with the ones coming from global criteria of risk, stability of humans, mobilization of vehicles and structural safety of wooden buildings

6.3.2 Implementation Methods

When using a reference threshold represented by a function like h ¼ h(U), it must be taken into account the large safety margin due to the uncertainties in the preparation, at a planning level, of the studies required for its practical evaluation. The aspects related to the uncertainty will be examined in detail in the next chapter. Now it can be anticipated that larger uncertainties about the main reference quantities regarding the evaluation of the flow velocities and, to a lesser extent, of the water depth. Indeed, the velocity is locally subject (inside the computational grid) to abrupt and relevant variations, which are very difficult to be foreseen, even by means of hydrodynamic model physically based and at high resolution. Main causes of the uncertainty are related to: (1) level of detail and precision of the topographic survey supporting the numerical hydrologic-hydraulic models, (2) high sensitivity of the mathematical 62 6 Hydrodynamic Criteria for Impact Evaluation models—even if they are 1D (monodimensional), pseudo 2D or 2D (bidimensional)—in comparison to the parameters of the resistance to the flow in the floodable areas. An additional cause of uncertainty, besides the previous ones, is the estimation of the flood waves, above all in terms of flood volume and peak flow. Moreover, the results of the hydrological and hydraulic modelling of the flooding flows in urban areas may differ, sometimes a lot, because of the different schematization, spatial resolution, boundary conditions and—last but not least—the technician working on the problem. Those remarks justify the adoption of adequate tolerance values, as it will be discussed later in this paragraph. As a homogeneous implementation of the risk bands at a regional scale is a fundamental need for an effective planning at that scale: It is also worth exploring if a simpler methodology, although approximated, could be able to ensure an appropriate robustness to the procedure. In a while, a simplified procedure will be described, based on the definition of the thresholds in terms of the relationship “water depth–slope”.Itis meant to avoid the estimation of the local velocity, using the slope in the place of the velocity, under the condition that the slope could be read in maps at an appropriate resolution. In this sense, it is also interesting to remember that the slope also has a certain importance to find the threshold for the stability of the humans (Abt et al. 1989; Maijala 2001). In fact, the experiments show that, for a given flow (velocity), the threshold tends to decrease when the slope is increasing, as mentioned before.

6.3.3 Hydrodynamic Threshold Water Depth–Slope

According to the Chézy equation, where the friction losses term is expressed through the Gaucker-Strickler-Manning formula, the slope of a steady stream ﬂow having a cross section with a width much higher than the water depth is:

À À4 ¼ ¼ 2 2 3 ð : Þ i J U ks h , 6 4 where J is the friction slope, in m/m, and ks is the Gaucker-Strickler roughness coefﬁcient, measured in m1/3 sÀ1. Putting the value of U obtained from the energy equation:

U2 E ¼ h þ ) U2 ¼ 2gEðÞÀ h , ð6:5Þ 2g into the expression (6.4), it comes out, for E ¼ (2S/γ)1/2: pffiffiffiffiffiffiffiffiffiffi À À4 À À4 À À4 ¼ 2 2 3 ¼ ðÞÀ 2 3 ¼ =γ À 2 3 i U ks h 2gE h ks h 2g 2S h ks h , that is: 6.3 Implementation of Hydrodynamic Thresholds 63

h ¼ hEðÞi : ð6:6Þ

In the same way, from the equation of the total dynamic force:

1 S gh S ¼ ρhU2 þ γh2 ) U2 ¼ À , ð6:7Þ 2 ρh 2 it is possible to obtain:

2 ¼ U ¼ S À g i 4 7 1 , 2 3 ρ 2 3 2 3 ks h ks h 2ks h that is:

h ¼ hSðÞi : ð6:8Þ

Then, imposing the condition:

h ¼ hiðÞ¼min½hSðÞi ; hEðÞi for a given roughness coefficient ks, the curves of Fig. 6.4 can be obtained. Such a solution looks quite sensitive, especially in the field sloped higher than 2‰, to the value of the roughness coefficient ks, as shown in Fig. 6.5. On the contrary, the thresholds are less sensitive to the roughness coefficient ks when the values of the slope are lower than 1‰. Moreover, such sensitivity increases when the tolerable total hydrodynamic force increases.

ks = 25 m^(1/3)s^(-1) 1.20 1.10 Force (N/m) 1.00 1000 0.90 1500 0.80 0.70 2500 0.60 5000 0.50 0.40 0.30 Water Depth (m) Water 0.20 0.10 0.00 0.01 0.1 1 10 100 Slope (%)

Fig. 6.4 Relationship between water depth and ground slope for a given total hydrodynamic force conditioned to the total head 64 6 Hydrodynamic Criteria for Impact Evaluation

The reference scheme based on the relationship h ¼ h(i) neglects a number of factors, like backwater effects of flood waves and the complexity of the unsteady flow in the flooded areas; at least in theory, such effects are (implicitly) considered by a threshold like h ¼ h(U). Moreover, the definition of the relationship h ¼ h(i) requires an a prior evaluation of the reference roughness, which is quite variable in real situations. Pertaining to it, it is possible to remark that in flooded urban areas the evaluation of the local roughness in detailed hydraulic models is subject to a (relevant) uncertainty, also because of the contemporary presence of relatively smoother surfaces (like, for example, paved roads) and important macroroughness (like irregular ground cover and street furniture). Yet, a criterion based on the relationship between water depth and slope of the flooded area has also some advantages, too: • The curves h ¼ h(i) are less sensitive to subjective evaluations from the technicians in comparison to the curves h ¼ h(U); • The curves h ¼ h(i) allows to keep into account explicitly the ground slope, which has a direct influence on the threshold of the human stability, as shown by the experiments about this issue; • In comparison to the criterion h ¼ h(U), a criterion h ¼ h(i) is easier to be implemented on the basis of the already prepared studies about the evaluation of the absolute risk; • A criterion h ¼ h(i), if implemented with slope classes, offers a definition that is simple and easy to understand, because the reference quantity is just the water depth. Those advantages are not negligible and therefore this approach deserves a certain considerations and can be implemented in the framework of expeditious study, (aimed) for example to find select the areas where it is better to focus detailed studies.

6.3.4 Use of Hydrodynamic Thresholds on the Basis of the Tolerance of the Results of Hydraulic Studies

For practical purposes, the deﬁnition of thresholds of either low or high relative risk requires an evaluation of the uncertainty margin of the main quantities (water depth, velocity and slope). The issues (relinked) to the uncertainty are discussed in the next chapter, where the different causes of the uncertainties are presented in the framework of the complex procedures for the evaluation of the hydraulic risk. In particular, when deﬁning the practical implementation of the thresholds, some reasonable safety margins must be added to the different reference quantities. If it is assumed that the tolerance in the evaluation of the stream velocities is equal to 0.5 m/s while 10 and 20 cm about the water depths, then the results are the thresholds h ¼ h(U) represented, for example, in Fig. 6.6. To determine those thresholds, the following hypotheses has been adopted: 6.3 Implementation of Hydrodynamic Thresholds 65

S = 1500 N/m 1.20 1.10 1/3 -1 k , m s 1.00 s 0.90 70 0.80 50 0.70 35 0.60 0.50 20 0.40 0.30 Water Depth (m) 0.20 0.10 0.00 0.01 0.1 1 10 100 Slope (%)

S = 2500 N/m 1.20 1.10 1/3 -1 k , m s 1.00 s 0.90 70 0.80 50 0.70 35 0.60 0.50 20 0.40 0.30 Water Depth (m) Water 0.20 0.10 0.00 0.01 0.1 1 10 100 Slope (%)

S = 5000 N/m 1.20 1.10 1/3 -1 k , m s 1.00 s 0.90 70 0.80 50 0.70 35 0.60 0.50 20 0.40 0.30 Water Depth (m) 0.20 0.10 0.00 0.01 0.1 1 10 100 Slope (%)

Fig. 6.5 Sensitivity of the hydrodynamic threshold water depth–slope to the ground roughness 66 6 Hydrodynamic Criteria for Impact Evaluation

• The tolerable value of the total hydrodynamic force, below which the relative risk is low, is equal to 1500 N/m; • The tolerable value of the total hydrodynamic force, above which the relative risk is high, is equal to 2500 N/m; • The ﬂow conditions with velocities above 2 m/s are very risky anyway, as reported by the literature about the safety of the buildings; • That the water depth threshold below which the relative risk is modes, is equal to 30 cm, as indicated by FEMA (2002); • That the mapping of the water depth is carried out for classes of the water depth, with a resolution equal to 10 or 20 cm.

Hydrodynamic Threshold in Terms of Water Depth - Velocity 1.00 h = h (U ) Force 0.90 Spinta (N/m) 0.80 alta High 1500 0.70 pericolositàRelative 0.60 relativaRisk 2500 0.50 0.40 0.30 Water Depth (m) bassa 0.20 Lowpericolosità Relative 0.10 relativa Risk 0.00 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Velocity (m/s)

Hydrodynamic Threshold in Terms of Water Depth - Velocity 1.00 h = h (U ) 0.90 SpintaForce (N/m) 0.80 alta High 1500 0.70 pericolositàRelative 0.60 relativa Risk 2500 0.50 0.40 0.30

Water Depth (m) Depth Water bassa 0.20 Low pericolositàRelative 0.10 relativaRisk 0.00 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Velocity (m/s)

Fig. 6.6 Discretized hydrodynamic thresholds expressed in terms of water depth and stream velocity: ΔU ¼ 0.5 m/s, minimum signiﬁcant water depth 30 cm, Δh ¼ 0.1 m (up) and Δh ¼ 0.2 m (down) 6.3 Implementation of Hydrodynamic Thresholds 67

When the focus passes to the water depth–ground slope criterion, it can be assumed that the water depths are estimated with a tolerance (for example 10 or 20 cm). In this case, it is also necessary to establish a signiﬁcant value of the roughness, and this assumption creates a remarkable approximation in respect to a possible real ﬂooding situations. Examples of practical thresholds with h ¼ h(i) shape are reported in Fig. 6.7. To determine such thresholds, again the following hypotheses have been assumed:

SOGLIA di PERICOLOSITA' RELATIVA (a) Discretized Hydrodynamic Thresholds of Relative Risk

1.00 0.90 Tolerable total hydrodynamic force:S S, N/m(N/m) 0.80 Modest relative risk: 1500 m

, 0.70 o

c Significant relative risk: i 0.60 2500 r d

I 0.50 e t 0.40 n a

r 0.30 i T

Water Depth (m) 0.20 0.10 0.00 0.01 0.1 1 10 100 Pendenza,Slope (%) %

(b) DiscretizedSOGLIA Hydrodynamic di PERICOLOSITA' Thresholds RELATIVA of Relative Risk

1.00 0.90 Tolerable total hydrodynamic force:S S, N/m(N/m) 0.80 Modest relative risk: 1500 m

, 0.70 o

c Significant relative risk: i 0.60 2500 r d

I 0.50 e t 0.40 n a

r 0.30 i

T 0.20 Water Depth (m) 0.10 0.00 0.01 0.1 1 10 100 Pendenza,Slope (%) %

Fig. 6.7 Discretized hydrodynamic thresholds in terms of water depth and ground slope of the flooded area: the tolerable total hydrodynamic force, below which the relative risk is modest, is equal to 1500 N/m, while the tolerable total hydrodynamic force, below which the relative risk is significant, is equal to 2500 N/m; the minimum significant water depth in terms of relative risk is assumed to be 30 cm, as indicated by FEMA (2002); the resolution for the classes of water depth is respectively Δh = 0.1 m (a) and Δh = 0.2 m (b) 68 6 Hydrodynamic Criteria for Impact Evaluation

• The value of the tolerable total hydrodynamic force, below which the relative risk is modest, is equal to 1500 N/m; • The value of the tolerable total hydrodynamic force, above which the relative risk is significant, is equal to 2500 N/m; • The reference roughness (according to Gauckler-Strickler formula) is equal to 50 m1/3 sÀ1; • The flow conditions with stream velocities higher than 2 m/s are very risky, anyway, as indicated by anyway, as reported by the literature about the safety of the buildings; • That the water depth threshold below which the relative risk is modest anyway, is equal to 30 cm, as indicated by FEMA (2002); • That the mapping of the water depth is carried out for classes of the water depth, with a resolution equal to respectively 10 cm (a) or 20 cm (b). Classifying the areas at a different relative risk level in terms of just water depth conditioned to the ground slope, it can be observed that the discretization, which is necessary to define compact and robust norm guidelines, also provides in this case classes of ground slope which are easy to recognize. This kind of approach is therefore useful to carry out preliminary studies in a quick way. Finally, to implement the proposed method, it is necessary to take into account the results of the experiments on humans. They indicate that the stability threshold is U Á h ¼ 0.6 m2/s for the humans. As it will be shown later, the condition U Á h > 0.6 m2/s concerning the stability of the humans, in addition to the hypothesis already assumed, can further influence the value of the threshold.

References

Abt SR, Wittler RJ, Taylor A, Love DJ (1989) Human stability in a high flood hazard. Water Resour Bull 25:881–890 Black RD (1975) Flood proofing rural residences. A Project Agnes Report, Pennsylvania New York State College of Agriculture and Life Sciences, Ithaca. Prepared for Economic Development Administration, Washington, DC Office of Technical Assistance Cacioli Paciscopi G (1999) L'asportazione idrodinamica degli autoveicoli in sosta nelle inondazioni urbane. Tesi di Dottorato di Ricerca in Ingegneria Idraulica. Università degli Studi di Firenze Economic and Social Commission for Asia and the Pacific (ESCAP) of the United Nations (1991) Manual and guidelines for comprehensive flood loss protection and management Federal Emergency Management Agency (FEMA) (2002) Guidelines and specifications for flood hazard mapping partners, February Maijala T (2001) RESCDAM: development of rescue actions based on dam-break flood analysis. Final report, grant agreement no. Subv 99/52623 Community Action Programme in the field of civil protection. Finnish Environment Institute, Helsinki New South Wales (NSW) Government (1986) Floodplain development manual. Australia Témez JR (1992) Control del desarrollo urbano en las zonas inundables. CICCP monographs. Madrid, Spain Chapter 7 Flood Proofing Methods

Alluvial plains and coastal areas are often the most fertile areas on Earth, along with soils of a volcanic origin. They are for this reason optimum areas for human settlements and urban construction because of their gentle topography. When speaking of alluvial terrain, it must be noticed that alluvium (from Latin: alluvies-ei or alluvio-onis: flood; etym., Latin: ab-luo: to wash and abolitus: cancelled, or even ab (Iove) pluvio: from rainy Jupiter1—Ancient Greek: ἀνα-λύω or ἁλλύω/ἁνλύω: to melt or to destroy; from ἁνά: above, and λoύω: to wash) indicates that this land was formed by floods and the associated river bed migration through millennia. There- fore, one often denotes the area as a floodplain.2 The coastline or a seashore is the portion of Earth where the land meets the sea or ocean, and the coastal area is the region where the interaction of the sea and land processes occurs. One must not blame our ancestors who founded present-day cities if some unsuitable location was chosen. Water being vital for all known forms of life, they exploited the abundant water resources available in alluvial areas, so accepting a certain degree of risk that extreme events could hit the urban settlement for all the advantages water gave. In ancient times transportation over water bodies, rivers and oceans, provided the major way of connecting people. We are told that ancient Rome originated from the flood that conveyed the cradle of two twins, Romulus and Remo, downstream the river to get the current city location. Around 50 floods were recorded in Rome from 753 BCE to the fall of the Western Roman Empire in 476 CE when Odoacer deposed the Emperor Romulus. In the first century CE Pliny the Elder wrote (Naturalis Historia, III, 55) that “Even

1Significantly, this defines inherent fatalism as an aspect of the common approach to such disasters both at that time and sometimes today. 2It is also interesting to see the connected etymology of flood: from Proto-Germanic floduz and Gothic flodus (verbal stem pleu,aspluvial, coming from Latin pluvius: rainy); from ancient Greek πλεω: to navigate and ἀπoλoύω: to wash (once again). Before: Sanskrit plavate: to navigate and Armenian luanam: to wash. Similarly deluge, from Latin diluvium and diluo (from dis-luo). Etymology may indeed be useful to understand present situations.

© Springer Nature Switzerland AG 2019 69 D. F. Bignami et al., Flood Proofing in Urban Areas, https://doi.org/10.1007/978-3-030-05934-7_7 70 7 Flood Proofing Methods though the Tiber river valley is prone to flash floods, there is no area in the valley where floods are as large as in Rome”. It seems that humans shall always live with the risk of floods, so they should assess the acceptable level of flood risk under their current social and economic standards. Defence measures are thus needed to reduce risk levels where and when these levels exceed those acceptable according to the above standards.

7.1 Overview

The previous chapters provide us with operational considerations on possible hydrodynamic criteria for assessing flood impacts that are due to the mechanical action of streams in terms of pressure and energy load onto building elements. As already mentioned, such reflections allow for the development of some specific recommendations that complement general criteria for land management and territorial policies. Among the most important issues are included infrastructure as well as urban and architectural planning, design and renovation, in regards to flood risk reduction, while also providing the inherent requirements and services. Such recommendations, in promoting Disaster Resilient Communities (DRC), may allow, as part of “hazard mitigation and preparedness management” actions (Pine 2015), for long term decisions in respect of territorial layout—e.g. in Italy via the River basin planning, which was established by Law 183/89 (and confirmed by subsequent Law 152/2006); or in France via the Plans de Prévention du Risque d’Inondation, established pursuant to Code de l’Environnement, (Law 565/1987) or via the Programmes d’actions de prevention contre les inondations (PAPI 2010). In parallel, during a flood event they enable civil protection services to undertake real time operations management. As an example, Italy adopted some Operating guidelines on organizational and functional management of national and regional early warning systems for civil protection against hydrogeological and hydraulic risks—Prime Minister Directive of 27 February 2004 and subsequent amendments. More in general, not only does it this occur at the EU Member State level, as provided for by Directive 2007/60/EC on the assessment and management of flood risks, but it is also provided by many other different national regulations according to their levels of territorial administration in many parts of the world. Within this framework, flood proofing methods and techniques are therefore a potentially solid reference in increasing resilience levels, as a factor among others, both for long term planning and emergency management of anthropic areas, in a perspective of increased adaptive capacity (Klein et al. 2003) and improved response preparedness (UNISDR 2015), respectively. 7.1 Overview 71

7.1.1 Alternative Ways of Protecting Urbanized Lands from Floods

From both standpoints (long term planning and emergency management), flood proofing techniques are meant as a focused micro-scale support to the community in defending itself from floods through an effective early engagement (not only a public but also a private one), working simultaneously to reduce mortality rates and to control the economic (and cultural) damages due to disasters (Chou and Wu 2014; Pine and Guillot 2015). All this mainly relates to rivers and lakes, yet it also applies to various situations in marine and coastal areas, such as storm, high-water and tsunami protection systems. Flood proofing comprises a series of actions with the aim of reducing local flood impact on human settlements. Since aseismic (or earthquake proof) buildings exist and are even built in areas with a high or very high risk of earthquakes, or, similarly, since houses can be improved to be fire-resistant in case of wild fires,3 we can construct flood-proof buildings as well, or, if possible, renovate or defend existing buildings or building compounds to that end. As a first example we note that in US risk areas it has been demonstrated since many years that, if wisely constructed, buildings are able to lessen flood impact by reducing the connected risk, thus influencing significantly the flood safety (see USACE 1995). Such risks are, obviously, to be considered as the expected losses—whether economic or not—in the reference time unit—usually one year—with regard to hazard, vulnerability and exposed value (see Fournier d’Albe 1979). In the framework of The US National Flood Insurance Program managed by The Federal Emergency management Agency, the definition of: “floodproofing” is “any combination of structural and non-structural additions, changes, or adjustments to structures which reduce or eliminate flood damage to real estate or improved real property, water and sanitary facilities, structures and their contents” (www.fema. gov/floodproofing). More explicitly, as mentioned in UNESCO’s document “Guidelines on non-structural measures in urban flood management” (UNESCO 2001)—probably the most acknowledged definition of flood proofing—It states that it identifies “the use of permanent, contingent or emergency techniques to either prevent flood waters from reaching buildings and infrastructure facilities, or to minimize the damage from water that does get in”. Correspondingly, but more technically, the UK Environmental Agency, in its document, “Temporary and Demountable Flood Protection Guide” (Ogunyoye et al. 2011), while speaking of a “portfolio of measures for managing flood risk”, gives the following categories of flood protection systems (as a synonym of flood proofing techniques): “Temporary, Demountable, Permanent”.

3See, for instance: https://www.ﬁresmartcanada.ca/ 72 7 Flood Prooﬁng Methods

In France, similarly, the ministries of Égalité des Territoires et du Logement and of Écologie, du Développement durable et de l’Énergie fixed the usefulness of retrofitting flood prevention works in existing and inhabited built environment by offering to professionals a specific guide (Fournier and Blas 2012)withthe aim of summarizing the possible adaptation measures to be applied to existing buildings to protect people, to reduce potential damages, and shorten rebuilding or refurbishment time. Generally speaking, flood proofing encompasses a broad range of possible actions to reduce direct flood damage to buildings, settlements, infrastructures or entire neighbourhoods. It comprises techniques of different kinds and complexity, to be deployed in accordance with the local properties of a potential flood (water level, flow velocity, soil nature, etc.) and to the territorial context of application. To date, the best-known techniques are those developed, adopted and promoted by the USA FEMA (Federal Emergency Management Agency). The UK has an approach that is equally good, but it is mainly focused on systems which remain distant or detached from single properties, while in France the devised systems are nearly always directly connected with buildings. In most cases, as far as urbanized territorial contexts are concerned, the American systems (in USA, but also in Canada4) cannot be directly adopted by most European and Asian countries, because they often need to be reconsidered or even reformulated, owing to the differences in the urban, industrial, hydrographic/ hydrogeological/climatic and geomorphological/geographical contexts. Later in this paragraph and in Sect. 7.2, some examples of flood proofing will be presented taken from the (extant) American literature, which so far has definitely been considered the most reliable state of the art in this field. Such descriptions will be rationally integrated throughout the present work, especially in order to originally define some variation strategies in the continental European contexts (and similar ones on other continents). The cited France and UK systems, from another point of view, are clearly more directly exploitable, albeit if partially, because of a necessary selection of use cases.5

7.1.2 Flood Prooﬁng Role

It is indeed a fact that in the last few years in Europe—and generally in the more mature economies—following a number of ﬂoods that affected almost all its

4See for instance Environment and Climate Change Canada web site, Reducing flood damage section: https://www.ec.gc.ca/eau-water/default.asp?lang¼En&n¼72FDC156-1 5Such a work of analysis (including Chaps. 7, 8 and 9) could be exploited in teaching programmes (it is, for instance, since 2015 part of the course of Land planning for environmental risk management of the Master of Science of Architecture of the built environment taught by Daniele F. Bignami and in the course of Hydrogeological risk and civil protection of the Master of Science in Environmental and Land Planning Engineering at the Politecnico of Milan). 7.1 Overview 73 countries (Barredo 2009; Lugeri et al. 2010), a new awareness and therefore an innovative connected industry and a rising market have taken hold simultaneously (White et al. 2016). Hence, these phenomena have started to influence the construction types in continental Europe, due to the increasing pressure caused by the significant damage that was caused by recent weather and climate events (Guha- Sapir et al. 2016). Europe today is less convinced that urbanized lands can be protected against floods only by means of massive public works like retention structures or flood detention basins, the availability of which, in terms of free land and of acceptability on a local basis, are becoming quite difficult. Likewise, massive structural works could be short-lived, since they disregard the uncertainties arising from the interactions with the flooded land, and the vulnerability of structures and infrastructures at risk (sometimes an ever-increasing risk). These measures reduce the frequency of inundations, but they do not affect flooding damages and losses once a plain is flooded. Structural defences are calculated to accommodate floods not exceeding a given magnitude, but they are highly inefficient when they have to cope with capacity-exceeding floods, especially when such defences were designed many years before, using insufficient data sets, which do not consider soil uses modifications and climate-change scenarios (Blöschl et al. 2015;Alfieri et al. 2016). Furthermore, Europe realized that population centres cannot be relocated (save in specific and limited portions), both because of the quantitative side of the issue—today, roughly, 20% of European cities with a population over 100,000 inhabitants are included in flood hazard zones (EEA 2012; Santato et al. 2013)—and often because those centers, hundred- or thousand-year-old settlements, rich in historical, cultural and artistic values, in many cases are a defining part of European identity itself—e.g. Florence, Rome and Genoa, Paris and Grenoble, Valencia and Barcelona, Lisbon, London, Glasgow and Sheffield, Dresden and Hamburg, Prague, Krakow, etc. (Cf. http://floodlist.com/europe). As regards the purpose of the present work, which focuses on reducing flood risk by defending properties, flood proofing techniques and systems offer a set of complementary actions, which, if compared to traditional strategies, are more flexible and of which the economic feasibility is easier to achieve, as shown, for instance, in the case of Bisagno river in Genoa (Cf. Bignami and Biagi 2018). This special point of view is given not only as an option to be pursued if the feasibility of large scale permanent protection systems is not adequate (Ogunyoye et al. 2011), but also as a realistic convincement regarding our future, because the economic, social and environmental sustainability of many kinds of large scale systems is more and more difficult to be achieved, at least within a reasonable time frame. Consequently, the traditional approach to flood-control must be integrated and completed adding new options, (in a framework of a bottom-up approach resilience-oriented), shifting flood-resistant actions towards a wider and complete “flood-adaptation” strategy. In other words, flood proofing techniques can represent the prevailing (multi-speed) dynamic component of a strategy not solely based on static solutions. Nonetheless, also flood risk reduction through flood proofing techniques can obviously result in partial, limited or relative values, especially if working unaided 74 7 Flood Proofing Methods by other strategies, particularly if compared to the usually expected performances of traditional works, such as artificial levees or other kinds of permanent structural measures. Therefore, coherently with our approach, Alexander (2002) suggested that communities should include citizens in risk reduction new processes (as asked by the EU), proceeding from nonstructural to structural measures, not vice versa; adding that no amount of investment in physical infrastructure, in related environmental assessments and in stakeholders participation will succeed in reducing risk to an acceptable level without a strategy integrated with other forms of risk management (as nowadays also stated by UNISDR in the Sendai Framework for Disaster Risk Reduction 2015–2030).

7.1.3 Flood Prooﬁng Options and Disciplinary Relations

Each flood proofing technique is obviously to be performed accordingly, whether the operation concerns the protection of new urbanizations from water or existing heritage buildings, respectively. Consequently, for presentation purposes flood proofing options will be divided into two main categories: Permanent techniques (also called passive) and Temporary techniques (also called active). The latter will then be divided into: – Removable (mobile and transportable, completely removed after flood event) solutions, – Pre-arranged/Pre-located (partially transportable and removed, partially pre-installed and fixed) solutions, – Demountable (fixed and liftable, but fully pre-installed; capable of being folded and unfolded) solutions, whereas the former (the permanent ones) will be complemented by several ‘smaller scale’ techniques. The former, i.e. permanent (or passive) solutions, are flood proofing works that are permanently arranged and undertaken in order to be lasting and do not require extra action before or during flooding (except for maintenance actions or surveillance which would alert the concerned authorities in case of failure). They usually act on risk factors such as vulnerability and value at risk for each building, on one side, and local hazard for building sites on the other. As mentioned below, attention should be paid to the fact that traditional large scale structural measures for flood control, such as embankment or flood wall improvement for the main sections of watercourses, detention (storage) basins or the naturalistic restoration of mountainsides, diversion channels do act on the hazard as well, although they should be normally considered to be protecting a vast area in lieu of individual buildings or neighbourhoods (in local contexts). These kinds of heavy permanent measures, not to be confused with the abovementioned permanent flood proofing techniques, are community or common infrastructures ones, basically public goods; flood proofing 7.1 Overview 75 permanent techniques, on the contrary, are often private or accessory properties, being linked to a specific edifice or to a small group of buildings. The latter, i.e. temporary techniques (or active), are divided into removable, pre- arranged/pre-located and demountable, and are activated during the event—but before water reaches those structures in need of defence or water rises to the lowest permanent defence level—by seizing as quickly as possible the chances provided by early warning against such disasters. After the event they are either removed (removable and pre-arranged/pre-located) or deactivated (demountable)—e.g. closed—thus revealing a protective function that is exclusively provisional and hinges on decisions made upon the circumstances. Hence, they mainly act on the factors of local hazard and vulnerability, rather than on value at risk. It should be noted that demountable (being fixed and liftable) solutions may also be deemed as a sort of semi-permanent solution (or active permanent solutions, considering as passive those we already referred to as permanent). They are installed or arranged permanently before it is known that a possible disaster is going to occur—during the preparatory period,amongterritorial equipment activities (see next chapter for a deeper analysis). They actually become operational only in case of need through more or less automatic (or manual) deployment mechanism, such as the raising of shields, which has to be integrated in the construction solutions. We do list demountable solutions among temporary techniques, as their effectiveness only relies upon the timely activation of the inputs by the monitoring systems that are supplied by the civil protection warning services (through their forecasting and alert capabilities) or by specific dedicated sensors detecting the unusual presence of water. They are generally more expensive than other techniques and are usually placed in high-risk and prestigious contexts—or, where there might be someone more inclined to invest (even if, generally speaking, the amount of such an effort must commensurate with the level of risk, in particular when public funds are involved). For this reason and for their dependence on higher or lower human response, temporary techniques, removable, pre-arranged/pre-located and demountable, seldom result in a change concerning flood hazard zones regulations—with the related building opportunities—and are incompatible, unlike some permanent flood proofing techniques, with some provisions which grant permission to build in relative risk zones—only on the basis of strict warranty conditions imposed by warning services (Cf. Ligurian Basin Authority 2005). Conversely, they happen to be particularly fit for the protection of existing properties which have turned out to be ill-advised in their position, unshielded or inadequately protected with structural measures for flood control (in particular when demolitions and/or relocations appear as unrealistic solutions). To complete this opening on different kinds of flood proofing techniques, we have to state also the possibility, in some cases, of implementing small permanent changes on buildings and infrastructures, which may be considered as an halfway solution between the two approaches (permanent and temporary), since they need smaller investment, similarly to of temporary techniques. 76 7 Flood Proofing Methods

Table 7.1 The different types of flood proofing techniques grouped by main categories following the classification shown above Flood proofing techniques: main categories (reducing local/micro-scale risk, additional or alternative to public structural measures acting at large/macro-scale) Permanent Small Perma- Temporary (building nent (build- Demountable Pre-arranged/Pre- Removable level) ing’s compo- (liftable and fully located (partially (mobile, trans- nent/feature pre-installed/fixed— transportable, portable, level) also called semi- partially pre-installed completely permanent) and fixed) removed after flood event) Not requiring extra action Put up during the event (active) during floods (passive)

Table 7.1 summarizes the different types of ﬂood prooﬁng techniques according to the main categories that we will discuss. From left to right, we go from permanent to fully mobile techniques. To achieve large scale dissemination and application as it would be desirable, the former group, i.e. permanent measures, and demountable (liftable) measures, among the latter, require new cross-connections aiming at long-term safety for the territorial layout as well as disciplinary and professional exchanges—in Europe as well as in other parts of the world—between hydrologists and, in general, experts in natural hazard defense (such as geologists, agronomists, forest scientists, etc.), on one side, and town planners, urban designers, architects and public work designers on the other. Particularly, as far asa possible contribution to planning and emergency management is concerned, the latter group, i.e. temporary measures, also require the abovementioned categories to establish a continuous, professional dialogue with experts in risk reduction as well as safety techniques and praxis, which are applied during the warning protection and emergency actions—therefore ‘real-time’—performed by different branches of the civil protection services. Figure 7.1 illustrates the scheme of the desired new disciplinary cross-connections.

7.2 First Level Classiﬁcation (Strategic Planning)

The main flood proofing techniques can be classified, coherently to what has been described in the previous paragraph, according to the following categories with regard to the strategy adopted in defending buildings: A. Relocation of the buildings, B. Elevation of the buildings, C. Floodwalls or levees, D. Dry flood proofing (external predisposition of a construction), 7.2 First Level Classification (Strategic Planning) 77

Fig. 7.1 Cross-disciplinary collaborations of flood proofing techniques which need to be improved to trigger the large scale spread of their applications in defending urban lands from floods

E. Wet ﬂood prooﬁng (internal predisposition of a construction). In addition to such categories, principally belonging to the ‘American school’,it is also possible to add a new, pioneering technique, under investigation or already under experimentation in various parts of the world: F. Floating. Furthermore, we can add another solution, recently focalized, acting on local morphology of the land where buildings have been constructed: G. Ground lowering/levelling of free land for waterway diversion and/or local storage. Permanent measures, hereinafter essentially described, provide solutions that are referable to each of these categories. The other measures described later, the temporary ones, will only provide some of the categories mentioned above.

7.2.1 Permanent Techniques

A. The Relocation is the safest strategy, as it eliminates the risk factor of exposed value.6 However, it is also, probably, the most expensive one: although it

6See the introduction to find the definitions of hazard, vulnerability and exposed value. 78 7 Flood Proofing Methods

Fig. 7.2 Symbolic scheme (left) and an example (right) of the ﬂood prooﬁng techniques of relocation (drawing of Elda Proietti)

reduces the emergency management public costs (in some cases also including insurance premiums) and damages that might be caused by a flooding. This requires the whole constructions to be removed in advance of the occurring of a flood and then relocated into a safe area (for instance out of the floodplain toward higher ground that is not exposed to flooding) and obviously a new site must be procured to replace the building. In addition, it is the only way to prevent any building from being, even if only partially isolated by water during a disaster, thus ensuring its full functional continuity. Such a technique can be applied both at the individual building and neighbourhood levels, allowing to free up land and therefore convert it back to its natural function or to a more suitable one for a floodplain (for instance sport activities). In the American context such a technique has sometimes evolved into spectacular solutions—like the transport on specific vehicles of whole buildings after literally detaching it from the ground (see for instance www.iasm.org, the International Association of Structural Movers web site). On the contrary, due to the abovementioned difference among the regions of the world in terms of construction types, the application of such a technique in Europe does not generally involve the repositioning of a structure but its demolition7 and rebuilding in a safer site, with all the related implications on costs, the disposal of non salvageable materials and the construction time (Fig. 7.2). B. The Elevation technique keeps all habitable and usable floors of a building above the maximum flood level. Such a “retrofitting” technique can be used on individual buildings whose structure and facilities prove to be solid and safe at the end of work—well anchored to the ground, hence with a very low residual vulnerability if compared to earlier conditions (considering flow velocity, waves, erosion, debris flow, etc.). In the American context, this technique quite often deals with positioning a structure that was previously placed on the ground on

7Some authors and institutions consider Demolition as another specific flood proofing technique, to be used in case of already damaged buildings, thus signalling and suggesting the option and the chance of rebuilding elsewhere, in safer places (Cf. Fema 2007—FEMA 543, Design Guide Risk Management Series). 7.2 First Level Classification (Strategic Planning) 79

Fig. 7.3 Symbolic scheme (left—drawing of Elda Proietti) and an example (right) of the ﬂood prooﬁng techniques of elevation

piers—or piles, posts and columns—or partially external closed foundations (on walls or on fill). It is obviously more difficult to use this strategy on masonry or reinforced concrete buildings, compared to buildings made of wood or other light materials. Particularly: in areas with a high level of seismic activity or wind, it can only be applied with great caution. Such a solution expects the building to remain isolated during the flood, unless some ‘overhead’ connections are set up with other buildings or higher grounds. From the functional and aesthetic (architectural) points of view, this technique may not be pleasing to the eye (Fig. 7.3). C. The installation of total or partial perimeter floodwalls,orlevees, prevents water from getting to the vulnerable parts of a structure by keeping it away from the exposed goods and reducing the site’s local hazard. Possible permanent works of this kind of technique (sometimes also called as belting) are small levees or berms (compacted fill with 2:1 or 3:1 slope) or walls (both placed on grounds with limited drainage). Local detailed orography permitting, these floodwalls can be applied only to some of the building’s sides, sometimes preventing the building from being totally isolated. As with relocation, this strategy can be adopted both at the individual building and neighbourhood levels. Its implementation, especially on this latter scale, demands being particularly cautious (as in the case of many flood control solutions to protect vast areas) while assessing that the obtained waterway diversion should not worsen the situation of other nearby—or connected—buildings, whether upstream or downstream (third party concerns) (Fig. 7.4). D. Dry flood proofing is obtained by sealing, structurally reinforcing and waterproofing a building—including its foundations—at least up to a range reasonably higher than the expected flood height (thus including the freeboard) to avoid flood waters from entering the buildings. Applying this usually less costly technique, protection may be provided by using shields for openings, sealants over the walls (polyethylene films, asphalts, new masonry layers, etc.) or even buttressing external partitions. In anyway, not only will such building types be isolated during the flood, but also partially submerged in water. In this case too, from the aesthetic (architectural) point of view, this technique may not be a desirable solution. A way to choose between this strategic option and the 80 7 Flood Proofing Methods

Fig. 7.4 Symbolic scheme (left) and an example (right) of the flood proofing techniques of floodwalls (drawing of Elda Proietti)

Fig. 7.5 Symbolic scheme (left—drawing of Elda Proietti) and an example of dry ﬂood prooﬁng technique (new masonry layer)

previous one (floodwalls) is to compare the forecasted pressure and level of the flood with the structural resistance of the buildings perimetrical surfaces (not easy in case of flood depths exceeding 1 m). E. Wet flood proofing, which supports the natural equalization of water pressure against a construction’s structures and walls (internal and external), is obtained by modifying individual buildings in order to allow water to flow in and out without causing significant damage—i.e. structure and infill restoration. This is possible, for instance, substituting carpets and wood planks with ceramic or unglazed tiles in rough finish, choosing aluminum, PVC and concrete for furniture, doors, etc., using elastomeric paint to walls (Figs. 7.5 and 7.6). It is important to emphasize that this latter technique, i.e. wet flood proofing, reflects a strategy of flood hazard management on individual buildings that follows a resilient approach (Lamond and Proverbs 2008)—which we will be defined hereinafter as locally resilient—implying the introduction of significant cultural and social changes in the way of living and conceiving the internal 7.2 First Level Classification (Strategic Planning) 81

Fig. 7.6 Symbolic scheme (left—drawing of Elda Proietti) and two examples (middle and right) of the flood proofing techniques of wet flood proofing

environments of a building (for instance transferring delicate components to a floor higher than the maximum flood level, including, if possible, most part of power and electrical plants) and the availability of an adequate warning time; furthermore, not often, a building could be inhabitable for a length of time or contaminated by chemicals, sewage or other materials. On the contrary, the previous techniques (relocation, elevation, floodwalls and dry flood proofing) are conceived as an approach resistance-oriented (Palliyaguru et al. 2014), which tends to be shared more quickly in the cultural and social domains by those people using a building, as its habitability and status are not compromised. Both dry and wet flood proofing works, though, reduce the vulnerability of a building to the action of water. Two of the above-mentioned techniques, i.e. floodwalls and dry flood proofing, can merge into a “hybrid” application, which allows an application at a neighbourhood level on perimeters where the external facades of the neighbourhood are waterproofed and the open spaces in between are connected by dedicated barriers. F. Floating, which is the most recent and experimental technique, adopts two main types of schemes, both with the aim of granting degrees of freedom of movement to individual buildings through water pressure: 1. ‘Continuous’ floating, which occurs because the building is not anchored or resting on the ground but lays directly on water, being positioned on a pre-existing stretch of water from the start. During the flooding, this building type has the same degrees of freedom of movement as a docked boat (but it is not a boat, obviously not being able to sail); 2. ‘Intermittent’ floating, which occurs only during the flooding. In this case the buildings foundations are designed to act as a piston (or a system of pistons), raising due to the hydrostatic pressure generated by the water that flooded their compartment—thus having only one degree of freedom that allows vertical movement along the height axis (extendable foundations). As a result, the building has a value exposed to the flooding that is close to zero as well as a reduced risk of suffering damage or losses during the flooding. 82 7 Flood Proofing Methods

Fig. 7.7 Symbolic scheme (left—drawing of Elda Proietti) and an example (right) of the flood proofing techniques of floating (www.bacahomes.co.uk)

This is also an example of a locally resilient approach of risk reduction, since the flooding occurs and affects the building—changing its status—but the building is soon ‘operational’ again. The former of the two sub-cases can better provide the building with some solutions connecting it to other buildings, constructions or grounds that might minimize its isolation during the flood. Logically, this technique (a hybrid between passive and active) is not apt to be used to retrofitan existing building, but has been devised to be applied to the conception of projects of new constructions (not buildable elsewhere, due to the rules and restriction of flood prone areas) (Fig. 7.7). Being this a new flood proofing strategic category, it is interesting to briefly show a couple of real cases.8 The first one is a European case, located on an island of the Thames (Buckinghamshire, UK), designated as Flood Zone 3b, where usually development should not be permitted. The building is famous as the UK’s first Amphi- bious House (Baca Architects). This kind of family home (named “formosa”) looks like a normal house in the most part of the year, but, when flooded, it shows its fully floating structure, exploiting an excavated “wet dock” made to allow water to enter and discharge naturally. The lower ground floor, internal and resistant to water pressure, is detached from this concrete structure, in this way letting Archimedes’ principle act when a flood event occurs, protecting the building up to two and half meters (level based on worst-case scenario of Environmental Agency). Services (electricity, water and sewage) are flexible, but four vertical posts (tested pumping water in the “wet dock” every 5 years) let the building gently ascend in a well-balanced manner when the river level rises, keeping habitable spaces safe above the flood level (www.bacahomes.co.uk). The second is an Asian case, studied for Thailand’s National Housing Authority to offer a solution to the recurrent floods affecting Thailand, in areas where to build homes with stilts or as rafts is not logical (because areas are far

8A hybrid case has been conceived in Netherlands: river homes with stilts are equipped with the possibility of floating up to 5.5 m of water level difference (anchored to mooring posts) when water rises at the liveable floor; this happens thanks to the action of hollow concrete bodies positioned immediately below (Koekoek 2010). 7.2 First Level Classification (Strategic Planning) 83

from rivers or sea and houses are built along roads). The amphibious houses designed by the Thai architect Chuta Sinthuphan (Site Specific Co. Ltd) are only inspired by stilts and rafts. The solution is modular and prefabricated (based on steel framing), to be lighter than traditional construction; it is based on four kind of building uses: residential, commercial, hybrid residential-commercial (common in many areas of Thailand) and civic. Under every kind of prefabricated building there is not a habitable part of the building, but a trench containing the floatation device, exploiting guideposts and pontoons filled with Styrofoam, devices able to let the building gently rise up to three meters (the forecasted maximum level of flood in the area where a “test-home” has been built) (asitespecificexperiment.worldpress.com) (Fig. 7.8). Similar, but on a bigger scale, is the case of the 2016 conceptual study by Third Nature called “Pop-Up”, an underground garage, actually not yet built, using an underlying reservoir to push it above ground as the reservoir fills with rain water (www.tredjenatur.dk/en/portfolio/pop-up/). G. Ground lowering/levelling of free land in proximity to those buildings or neighbourhoods in need of protection can be planned both for flow deflection purposes and for the storage of small volumes or streams of flooded water (even underground). Such a solution, which can be accompanied by the elevation of buildable areas and setbacks of property lots (for instance obtaining a defensive slope), stands out as a resistant solution that reduces the risk by basically acting on local hazard. Normally it does not cause the isolation of buildings when floods occur. Compared to previous solutions, its effectiveness depends more on flooded water volumes, on local land morphology and, in general, on the territorial and environmental contexts. This type of technique is easily inferable from the construction of levees or floodway channels, as, in a planar represen- tation, the latter is mainly characterized by a one-dimensional or linear surface, while in this case the geometrical structure is two-dimensional. However, it differs from flood detention basins for its small scale and the broad variety of land use. This solution is more suitable for various contexts of small European drainage basins9 rather than North-American great basins, where the first five solutions mentioned above were technically formulated. Its implementation, especially for outdoor living areas at the neighbourhood level through proper works of grading and excavation, once again demands caution while assessing that the obtained waterway diversion does not worsen the situations of other nearby buildings, whether upstream or downstream (Fig. 7.9).

9As an example of regulatory implementation of this technique, in Italy the River Po Basin Authority stated that in “B flood prone areas” (fixed expected level of flood) it is forbidden to perform ‘actions resulting in a significant reduction or partialization of basin capacity, unless such actions entail an equal increase in the basin capacity of other hydraulically equivalent areas’ (Article 30, Implementing rules of Hydrogeological Setting Plan of 26 April 2001, pursuant to Article 17 of Italian Law 183/1989). 84 7 Flood Proofing Methods

Fig. 7.8 The amphibious houses designed by the Thai architect Chuta Sinthuphan (Site Speciﬁc Co. Ltd)

In this case too, being this a new flood proofing strategic category, it is interesting to briefly show real cases of its use. The application of the latest technique above mentioned has been tested in a recent real case, the Rotterdam water square; there the technique was integrated from the start with the initial stages of the design process. Rotterdam presents itself as the first city in the world to have a full-scale water square: “When it is dry, the square offers nice spots for basketball and skating. During heavy rainfall, the square’s basins retain water from the square and the surrounding rooftops, at approximately 1.7 million litres. This water is retained, keeping it away from the sewage system, preventing urban floods” (Benthemplein page in Rotterdam Climate Initiative web 7.2 First Level Classification (Strategic Planning) 85

Fig. 7.9 Symbolic scheme (left—drawing of Elda Proietti) and an example (right) of the ﬂood prooﬁng techniques of Ground lowering/levelling of free land

Fig. 7.10 Benthemplein (Rotterdam) full-scale water square (De Urbanisten 2011–2013, www. urbanisten.nl): the square’s basins retain water from the square and the surrounding rooftops (top: renderings when weather is good, on the left; and when it is rainy, on the right; down: square’s water flow scheme, on the left; and the square as it recently was at the webcam) site http://www.rotterdamclimateinitiative.nl). In this specific case the project is designed having nearby sewers adapted to optimise the square’s water function: the drainpipes from the surrounding buildings are detached from the sewage system, the water at present flows from the buildings to the central basins. In other situations and contexts, this type of solution could also be applied to divert (or to temporaneously store) water flows coming from upstream locations (Fig. 7.10). Similarly, we can mention the case of the “Waterside park” at Villeneuve-le-Roi (Val-de-Marne, Grand Paris, Île-de-France), beside the Seine, recently realized by Florence Mercier. The park, having a surface of 0.85 ha, is not only a lively place for inhabitants and a slice of nature in an urban environment, but it also has a function of collecting and regulating the local runoff in case of storm water, thanks to the “finely 86 7 Flood Proofing Methods

Fig. 7.11 Rubattino, Milan: an industrial area under decommissioning which is located in a C near to B flood-prone area characterised by small differences in height: a hypothesis of an off-site soil levels lowering/modelling to be potentially carried out to reduce flood local hazard (Politecnico di Milano, Laboratory of Urban Design of professors G. Goggi, R. Rosso and D.F. Bignami) tuned” topographic works on the different ground levels (http://www.fmpaysage.fr/ en/projets/parc-du-quartier-du-bord-leau/). This type of approach has also been conceived to work on the urban regeneration of “Rubattino” area,10 in Milan, Italy, an industrial area in the East of the city, under decommissioning. Rubattino is located in a C (catastrofic level) near to B (fixed expected level) flood-prone area of the Lambro river, part of the Po River Basin Authority. Several real estate development projects of the area have been proposed, every time substantially neglecting the fact that the surfaces of the area are characterised by small differences in height among themselves. Our suggested hypotheses include an off-site (or even an on-site) soil levels lowering/modelling to be carried out to reduce flood local hazard and to store and deflect forecasted water flows. This integrated urban intervention idea could be named “Urban Water Park” (the area is included in the Po river Hydrogeological Setting Plan and in the new flooding areas mapped on the basis of the new EU flood directive) (Fig. 7.11).

10Works were developed during the Laboratory of Urban Design of the Politecnico of Milan (Master on Architecture) coordinated by G. Goggi, during which, as far as ﬂood problems were concerned, the students supervision was responsibility of R. Rosso and D.F. Bignami. 7.2 First Level Classiﬁcation (Strategic Planning) 87

Fig. 7.12 San Donato Milanese (Milan): urbanized C and B ﬂood-prone areas: a hypothesis of soil levels lowering/modelling to be potentially carried out to reduce ﬂood local hazard [Politecnico di Milano, course of Land planning for risk management (Master of Science on Buildings Archi- tecture) taught by D.F. Bignami]

Such an approach has been similarly hypothesized also along the Lambro river, while working on the local disaster risk reduction strategies for the urban regeneration of San Donato Milanese11 (also near Milan) (Fig. 7.12). Another interesting example, although more technical and less innovative from an urbanistic point of view, is that of Toronto. In that city some important public

11Works were developed during the course of Land planning for risk management of the Politecnico of Milan (Master on Buildings Architecture) taught by D.F. Bignami. 88 7 Flood Prooﬁng Methods

Fig. 7.13 Toronto: public works on underground storage tanks designed to face overloaded urban sewer systems and overland drainage routes (city of Toronto Basement Flooding area 37 Display Boards) works on underground storage tanks are already under way or planned to face cases when urban sewer systems and overland drainage routes can become overloaded to act as temporary detention and slow release to the receiving sewer, reducing the potential flooding (city of Toronto Basement Flooding area 37 Display Boards, Published on May 4, 2016—slideshare.net). Similar is the case of Tokyo, even if at infrastructural level, where, contemporaneously, guidelines are distributed suggesting solutions to the private owners to protect permanently their underground cellars in residential buildings and ground level shops, and a giant public network of underground tunnels and caverns has been built and anti-inundation measures for underground stations of Metroto has been undertaken (Aoki et al. 2016) to keep the city safe during extreme storms and floods (Figs. 7.13, 7.14 and 7.15). Remarkably interesting is also the case of Bordeaux (France), where the urban community is vulnerable to the variations of the Garonne river as well as to ocean tides and storms from the Atlantic. To prevent flood risk, a waste water management system called RAMSES (Régulation de l’Assainissement par Mesures et Super- vision des Equipements et Stations), actively manages runoff storage in the numerous dedicated structures (pumping station, collectors, relief ponds, etc.) and fights against floods evacuating millions of cubic meters of stormwater. Recently, the system has been improved by new water gates, built to prevent stormwater from being released into the Garonne, and by new underground storage and pump systems, integrated in the net of defense (Fig. 7.16). The two following tables outline the main features of the abovementioned strategies with regard to both operational and analytical attributes (Tables 7.2 and 7.3). 7.2 First Level Classification (Strategic Planning) 89

Fig. 7.14 Tokyo: guidelines of the solutions to permanently protect underground spaces

Fig. 7.15 Tokyo: a cavern part of the giant public network of underground storage net built to keep the city safe during extreme floods (https://interestingengineering.com/tokyos-futuristic-under ground-flood-system) 07FodProo Flood 7 90 fi gMethods ng

Fig. 7.16 Bordeaux: a new portion of the water management system built to protect the city from ﬂoods (www.bordeaux-metropole.fr, 2016) 7.2 First Level Classiﬁcation (Strategic Planning) 91

Table 7.2 Summary of operational features upon application of permanent flood proofing techniques Permanent flood proofing Summary of operational attributes Isolation during Individual Neighbourhood Technique flooding building level level A. Relocation No Yes Yes B. Elevation Yes Yes No C. Floodwalls According to local Yes Yes morphology D. Dry flood proofing Yes Yes No E. Wet flood proofing Yes Yes No C/D. “Floodwalls—Dry flood According to local No Yes proofing” Hybrid morphology F. Floating Yes Yes No G. Ground lowering/levelling of No (If correctly Yes Yes free land applied)

Table 7.3 Summary of analytical features upon application of permanent flood proofing techniques Permanent flood proofing Summary of analytical attributes Risk reduction action Approach to local Technique (factor) territorial safety A. Relocation Exposed Value 1-Flood-resistant B. Elevation Vulnerability 1-Flood-resistant C. Floodwalls Local Hazard 1-Flood-resistant D. Dry flood proofing Vulnerability 1-Flood-resistant E. Wet flood proofing Vulnerability 2-Flood-resilient C/D. “Floodwalls—Dry/Wet flood Local Hazard and 1-Flood-resistant proofing” Hybrid vulnerability F. Floating Exposed Value 2-Flood-resilient G. Ground lowering/levelling of free Local Hazard 1-Flood-resistant land

7.2.2 Temporary Techniques

The main temporary actions include even more techniques, which are put in place by finding a quick solution set-up and are used upon activation of specific alert phases by the locally assigned warning service of civil protection (including both forecasting and alert processes). Such actions are aimed at obtaining the same results as permanent flood proofing techniques, especially those oriented to a resistant approach and risk reduction through a decrease of the local hazard and vulnerability factors (never through a decrease of the exposed value). Although some performances are partially reduced or engender a relatively higher uncertainty of results, 92 7 Flood Proofing Methods they have a number of other qualities; notably, for instance: they are generally less expensive than permanent ones, even though they are able to avert significantly greater losses than their actual implementation costs; they have a lower impact on landscape and architecture—building aesthetics and functionality; they require few changes in the status and use of locations and their related constructions—for these two reasons they are more suitable than permanent ones to protect cultural heritage buildings; they are moveable, though only partially in the case of demountable ones, whereas pre-located and removable techniques are also transportable and even reusable in different sites or multiple cases; they are gradually/partially implementable, thus in many cases allowing flexible tactics of defense. In particular, such techniques are essentially based on the following selection of the strategic classes presented above: – C. Floodwalls, namely: Removable groups C.R.1, C.R.2, C.R.3, C.R.4 (Floodwalls Removable groups 1, 2, 3 and 4), Pre-arranged/Pre-located group C.P.1 (Floodwalls Pre-arranged/Pre-located group) and Demountable group C. D.1 (Floodwalls Demountable group) of the list in the following paragraph; – D. Dry flood proofing, namely: Removable groups D.R.1, D.R.2 (Dry flood proofing Removable groups 1 and 2), Pre-arranged/Pre-located group D.P.1 (Dry flood proofing Pre-arranged/Pre-located group) and Demountable group D.D.1 (Dry flood proofing Demountable group) of the list in the following paragraph; – C/D. Combination of both, group C/D.1 of the list in the following paragraph. – E. Wet flood proofing, namely: Removable group E.R.1 (Wet flood proofing Removable group) of the list in the following paragraph. – G. Ground lowering/levelling of free land, namely: Removable group G.R.1 (Ground lowering/levelling of free land Removable group) of the list in the following paragraph. In detail, the sub-classes or groups we here suggest to group the increasing variety of temporary flood proofing techniques, as shown in Chap. 9, are C.R.1 (Floodwalls Removable group 1)—Stacking of individual base units filled with solid materials acting on gravity, including traditional emergency dikes made of sandbags—which are a sort of benchmark of our classification—temporary dikes containing reinforced earth/loose soil, as well as bags filled with innovative absorbent materials; C.R.2 (Floodwalls Removable group 2)—Supportive/juxtaposed use of fluid containers, including modular tubes or containers to be filled with air or water (temporary barriers); C.R.3 (Floodwalls Removable group 3)—Self-deploying or self-supporting mobile barriers, including self-inflating barriers or barriers with a reticular structure; 7.2 First Level Classification (Strategic Planning) 93

C.R.4 (Floodwalls Removable group 4)—Emergency dikes and/or berms of loose solid material, including temporary earth levees/dikes and barriers of stone/ concrete blocks; C.P.1 (Floodwalls Pre-arranged/Pre-located group 1)—Temporary barriers/ shields with especially crafted anchoring (temporary waterwalls), including temporary anchored vertical barriers (shields, gates and panels); C.D.1 (Floodwalls Demountable group 1)—Fixed retractable barriers including some automatic vertical gates (barriers); D.R.1 (Dry flood proofing Removable group 1)—Full dry flood proofing of buildings, including the wrapping and the packing of vertical walls with waterproof sheets (panels); D.P.1 (Dry flood proofing Pre-arranged/Pre-located group 1)—Selective dry flood proofing with customized watertight protections, including temporary shields or panels, watertight seals to prevent potential water seepage into the buildings (one-piece or sectional, thus more innovative than wooden boards); D.D.1 (Dry flood proofing Demountable group 1)—Selective dry flood proofing with demountable watertight protections, precisely and permanently customized, including watertight doors and windows and some automatic vertical shields; D.R.2 (Dry flood proofing Removable group 2)—Complementary dry flood proofing of buildings by means of removable universal apparatus, composed by industrially produced devices thought to seal the most of common openings; C/D.1—Mixed solutions and special cases, either cooperating—supporting one another—or collaborating—working side by side (including techniques to protect special outdoor goods). E.R.1—(Wet flood proofing Removable group 1) Hydro-repellent sacs or similar protections systems for indoor movable goods, as big sealable plastic bags; G.R.1—(Ground lowering/levelling of free land Removable group 1)—Water diversion temporary activated pipes or bridges, composed by devices which do not stop but deviate water.

7.2.3 Small Permanent Techniques

To complete the previous statements on the main objective of this work, we now mention what could be defined as a sub-category of techniques, which is represented by a series of solutions based on small permanent changes to buildings and infrastructures (and their adjacencies), which may be considered a halfway solution between the two approaches. Such operations are classified in the following four categories of permanent measures: floodwalls (C), dry (D) and wet (E) flood proofing, ground lowering/levelling of free land (F). However, both for their limited dimensions and because they do not produce any radical changes to the positioning or to the features of the building itself, it is assumable that they can be performed 94 7 Flood Proofing Methods through as important investments as those required for temporary techniques, and therefore they can be a potential alternative or in closer synergy with them. Sometimes such actions cannot be applied for technical rather than for economic reasons. Likewise, they sometimes are only partially—however usefully—effective (as in the case of vast areas flood control solutions), while in other cases, like temporary techniques, they alone can prevent quite significant losses, sometimes significantly greater than their actual implementation costs. Here are some instances of ‘smaller scale’ permanent measures: C. Small permanent Floodwalls Small elevations (berms) made of soil or other materials (concrete, bricks), just in front of building entrances (doors, basement window, etc.) or of transport infrastructures; light sea walls made of wood, glass or other materials (both techniques are considered special kinds of floodwalls); D. Small permanent Dry flood proofing Air-bricks that under flood conditions uses the rising water to automatically shut off12; concrete, brick and (external) masonry waterproofing-sealer or hydro-repellent paints or protectors; waterproof non-opening windows made with glass blocks or with reinforced glass; back-flow (non-return) valves in sewage/drainage systems, for instance with flaps floating up to block back-flow from sewers (as a special kind of dry flood proofing); E. Small permanent Wet flood proofing Dual function flood vents that counterbalance the pressure on internal and external walls of buildings; hydro-repellent paints or materials on internal walls; elevation of critical appliances and electrical outlets (these techniques are among the principles on which permanent wet flood proofing is based). F. Small permanent Ground lowering/levelling of free land Artificial drainage channels and slopes diverting water from buildings; moving flaps (sometimes to be opened when necessary) or drainage preferential ways favoring the water flows, avoiding stagnation (as a special kind of ground lowering/levelling of free land) (Figs. 7.17, 7.18 and 7.19). The following table outlines the different floodproofing options, connecting categories with possible strategies (Table 7.4).

7.3 Design and Assessment Principles: Introduction

In practical terms, the choice of the best flood proofing technique should consider multiple factors. In short, the most considerable factors include the types of building, foundation and construction materials as well as the features of the chosen site, such as soil type, gradient and permeability. The real conditions of hydraulic risk are of the utmost importance, especially water level, flow velocity, flood speed and the

12This technique is assigned to the group of the small permanent ones, as back-flow valves, because it does not require human action in case of need, nor energy supply (as it is necessary to supply in the case of automatically actioned demountable (liftable) flood proofing solution). 7.3 Design and Assessment Principles: Introduction 95

Fig. 7.17 Small elevations (also designed to possibly set up flood-gates) at the entrance of the new Milan underground line (M5—Piazzale Istria), near the Niguarda district, designed for handling the problems of the flood-prone area which are caused by the floods of the Seveso river

Fig. 7.18 The new Milan underground line (M5) during a 2014 Seveso flood. Small elevation “in action”, showing its efficacy in avoiding huge damages to railways 96 7 Flood Proofing Methods

Fig. 7.19 Example of street furniture bike stand as small permanent technique of raising ventilation grates to reduce subway ﬂooding risk in case of storm (Source: MTA NYC Transit)

Table 7.4 Summary of floodproofing choices between categories and strategies options P. Temporary D. R. Pre- Temporary Small Temporary arranged/ Demountable Category\Strategy Permanent Permanent Removable located (liftable) A. Relocation X –– – – B. Elevation X –– – – C. Floodwalls X X C.R.1, C.R.2, C.P.1 C.D.1 C.R.3, C.R.4 D. Dry flood proofing X X D.R.1, D.R.2 D.P.1 D.D.1 E. Wet flood proofing X X E.R.1 –– F. Floating X –– – – G. Ground lowering/ X X G.R.1 –– levelling of free land presence of debris flow. In the case of temporary defenses, other factors are also to be considered, such as forecasting, flood alert and mobilization systems. For instance, in the United States, the U.S. Corps of Engineers (USACE 1995) created the so-called Flood Proofing Matrix to report a summarized version of the potential records for practical use situations of flood proofing construction techniques (see Fig. 7.20 where the flood proofing matrix by the FEMA, in an updated version, is displayed). On the basis of the most significant project variables, the matrix suggests which types of flood proofing measures are appropriate for 7.3 Design and Assessment Principles: Introduction 97 individual structures and can be implemented. This chart is obviously just for reference, so the effective decision must be considered on a case-by-case basis, particularly on account of the properties of the target site and for the specific applicable legislation. Moreover, the matrix applies specifically to American lands, whose characteristics are often different, for instance, from European and Asian ones in terms of land morphology and characteristics of flood events (for an Italian case of application, see Bocchiola and Rosso 2006, and Fig. 7.20). In Italy—but not exclusively—in some regions such as Liguria (Ligurian Basin Authority 2005) the regulations on soil usage in flood-prone areas have introduced the concept of relative hazard. This implies a preliminary hazard model which is addressed to identify those zones where (permanent) flood proofing measures may be an acceptable solution, being able to match the needs of territorial development with those of efficient flood defense activities. As already mentioned, for such a purpose the assessment of water levels and flow velocities in the event of a flood is essential to plan efficient and effective actions (see Fig. 7.21).

Fig. 7.20 Centa River at Albenga (Image by satellite ASTER®) and Map of applicable Flood Prooﬁng techniques. Buildings with a social or administrative function are highlighted 98 7 Flood Prooﬁng Methods

Fig. 7.21 Flood Proofing Matrix (USACE 1995, updated 2012). N/A, not advisable; 1 Special protections to withstand erosion; 2 No time for human intervention; these measures must perform with basement openings unobstructed and big enough to promptly restore the balance of hydrostatic pressures; watertight protections (sluices, etc.) permanently in operation; no last-minute measure in case of wet flood proofing. 3 Protection against percolation below walls and foundations. 4 Ice and debris loads should be considered and accounted for in the design of foundations and floodwall/ levee closures. 5 Temporary relocation in case of renovation. 6 Not advisable in this situation, unless a specific engineering solution is developed to address the specific characteristic or constraint (image from Engineering Principles and Practices for Retrofitting Flood-Prone Residential Struc- tures (Third Edition) FEMA P-259/January 2012) 7.4 Temporary Flood Proofing as an Emerging Strategy for Adaptation and... 99

Thus, the development of flood proofing techniques (permanent and temporary) entails a more detailed and complex knowledge of floodings, since the possible behaviour of the system should be forecasted with fine spatial detail (see Fig. 7.20). It therefore envisages a new generation of hydrological studies and demands research to make an effort towards a deeper knowledge of how water can interact with land and, above all, with the built environment and human defensive reactions. It is a new frontier of scientific investigation, which we feel confident in facing thanks to the current observation and calculation tools even in the most complex European context, which is morphologically and urbanistically different from the land where the American school of thought emerged, and thanks to an enhanced degree of innovation applied to the civil protection planning activities. In addition, one can easily note that this matrix does not distinguish between permanent and temporary techniques, as they are presented in this book. Logically, the usefulness of the matrix is still relevant in the context where was created concerning, the United States floodplains. Differently, it is not always likely to have the possibility to consider every alternative in other regions and countries of the world. In particular, to choose permanent techniques it is frequently impossible—for instance: as already said, it is not possible in Europe, due to the heaviness of the building components; nor is it possible in many parts of Asia and Africa, due to construction techniques based on materials that are not strong enough to preserve themselves from the action of water.

7.4 Temporary Flood Prooﬁng as an Emerging Strategy for Adaptation and Regional Resilience

The necessary assessments to choose among the available temporary flood proofing techniques encompass all the introductory factors that have just been mentioned above. More will be illustrated in the following pages. First of all, it is important to know that strategies like the one presented in the map of Fig. 7.20, which is noticeably based on permanent techniques, do represent case studies situations that are helpful for raising considerations on the issue, considerations which can be used to break through some sort of inertia towards action. Nonetheless, we could define them as ‘ideal’, not indeed for the risk that they must deal with but for the hypothesis of a response to risk that has been formulated without any real budget and implementation time limitations—considering the extent of the territorial scale and the large amount of operations that need to be performed at the building scale. In most cases, if such a strategy could be economically achievable, it would most likely be on the basis of long-term plans only—for several decades. All the same, these plans do involve transitional periods of implementation that should last long enough, if compared to the recurrence intervals of the floods 100 7 Flood Proofing Methods from which we seek protection (starting from a return period of 2–5 years13), to require a massive use of temporary protection mobile measures. In accord to these considerations, but not only, this text will emphasize, in the next pages, temporary rather than permanent measures. More generally, on the basis of these considerations, this work wishes to point out that the first step towards the proper use of flood proofing solutions is not a matter of picking up a technique, but the defining of a defence strategic planning of flood risk reduction measures through flood proofing techniques, a plan that not only aims at correctly identifying a framework for implementation— starting with the choice between permanent and temporary measures—from a mere practical point of view, but also at times, economic and performance levels—along with the inevitable decisions on risk acceptability (and its thresholds). It is therefore easier to understand the specific goals of the following part of our work, which is mainly to foster knowledge of temporary flood proofing techniques to be promptly deployed during urgent situations. This would imply a cultural action which might raise the awareness of risk situations and then spread responsibility as concerns the need to adopt measures to reduce them. Such cultural action is the necessary precondition to encourage a better implementation of flood proofing solutions, both at a technical level, to allow for its appropriate use according to different exposure and response situations, and at an effectiveness level, depending on the relationships between the needs and the available resources. The intended target is to foster the innovation of management methods for these types of disasters in the European contexts and in similarly developed countries, especially by enhancing the current real-time risk reduction capacity of the operational sections of civil protection. In doing so, more favourable conditions would be generated for the post- disaster recovery capacity of lands by the increase of their regional resilience (or of a wide area), since their event-related losses have been reduced through specific actions, which are undertaken to broadly improve local resistance and resil- ience14—namely at individual building or neighbourhood levels. It would be fundamental to achieve results in this respect in order to provide more modalities of protection for the population centres located in the most significantly urbanized lands in a context of lack of available public resources. This is due to both extensive structural measures of soil protection, traditionally well-accepted by the populations

13This is the first stage of recurrent cases of floods caused in urban areas through heavy pluvial events, falling on inadequate sewer systems which being overloaded, may fail owing to inadequate maintenance or poor levels of renewal investment. 14On the varied characteristics according to the territorial action level for the concepts of resilience and resistance, see also Bignami (2010) and Palliyaguru et al. (2014). Here it should be noted that the broad improvement of local resistances has improving effects on general, or wide-ranged, resilience. 7.4 Temporary Flood Proofing as an Emerging Strategy for Adaptation and... 101

(Werrity et al. 2007), measures which sometimes cannot even be implemented,15 and to massive, more compatible relocations with a sustainable use of soil, often objectionable for the residents. Such measures, which belong to strategies based on the regional resistance approach (or of wide area), are no longer able to meet, as already said the population’s legitimate expectations. The ultimate objective is to provide, at regional-level, decision makers with a new ‘weapon’ to overcome flood-related effects, above all having in mind the goals of enhancing adaptation and risk reduction actions as we find in the frame given by the Sendai Framework for Disaster Risk Reduction 2015–2030 (UNISDR 2015, https:// www.unisdr.org/we/coordinate/sendai-framework). Coherently, in this work, and precisely in the next chapter, we will focus on these temporary techniques, namely flood proofing techniques to be implemented during a civil protection operation in the event of a flood emergency (involving citizens actions). We will therefore attempt to provide their ‘categorization’ according to the varied peculiarities in respect to scenarios, potential performances as well as technical and time preconditions of application—during the warning or alert phases. As we shall see, they offer the ideal features to stand out as a protection tool for many European contexts (and similar), especially (but not only) in environments that have been urbanized far beyond the limits, even more so in a scenario of climate change which appears to be, with a certain probability, more and more worrying.16 Such limits would indeed have been respected, if the necessary risk analysis, at this stage essential to plan flood proofing operations, had been promptly internalized, for instance, in public and private real estate investment or construction projects and plans (Brugmann 2012; Bignami 2014; MM Council 2016). Nevertheless, the owners and managers of buildings in flood hazard areas do often find the implementation of risk adaptation measures almost or quite unnecessary (Grothmann and Reusswig 2006; Quade and Lawrence 2011), even from a mere economic point of view—notwithstanding the fact that Intergovernmental Panel on Climate Change recently affirmed that “The severity of the impacts of climate extremes depends strongly on the level of the exposure and vulnerability to these

15Impossibility due not only to economic reasons, but also because, sometimes, great losses and significant damages could come in very small basins caused by very modest watercourses, where extensive structural measures are often not feasible. 16In the Special Report of the Intergovernmental Panel on Climate Change “Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation—Summary for Policymakers”, is reported: “There have been statistically significant trends in the number of heavy precipitation events in some regions. It is likely (66–100% probability) that more of these regions have experienced increases than decreases [...]”. “Economic losses from weather- and climate-related disasters have increased, but with large spatial and interannual variability (high confidence, based on high agreement, medium evidence)” (IPCC 2012). 102 7 Flood Proofing Methods extremes (high confidence)17” (IPCC 2012). For this reason, too, this book aims to be of some use not only for technical advancement, but also for the growth of cultural awareness, avoiding the most common mismatches between Disaster Risk Reduc- tion (DRR) and Climate Change Adaptation (CCA) (Birkmann and von Teichman 2010). CCA actions certainly include DRR ones, but many other times CCA local engagements, acting on a global or large scale, do not directly nor immediately decrease disaster scenarios of the same communities or citizens, but are effective only in the long period and if only widely applied.

7.4.1 Defending the Value of Property Investment

A well-established use of these techniques is hindered by the, basically incorrect, idea that implementing measures to protect buildings from flood events would lower their market value, thus revealing the risk condition in an indirect manner. Still, these techniques essentially defend the value of their investment. The ostensible paradox is explained by considering that, because of a failure in market and land renting mechanisms, real estate appraisals quite often do not incorporate the negative externality caused by mistaken building placements and/or mistaken land management with regard to water cycle. In our days, the time has come to fix such a failure and this could not be delayed much longer. From this point of view, we would like to highlight that real estate often suffers from a technical and cultural backwardness if compared to other industrial sectors—a state of affairs that needs to be remedied. In particular, this is due to the fact that in most cases builders are not going to make use of their constructions. As an example, in 2009 the International Standard Organization (ISO) issued the regulation “Risk management—Principles and guidelines; reference number: ISO 31000:2009”, where, among other things, it is pointed out that risk management “creates and protects value, is part of decision making, explicitly addresses uncertainty and is transparent and inclusive”. The time has come to sweep away the last hesitations. The territorial management of disaster risk reduction for real estate assets is soon to be approached in a more modern and integrated way; for instance by choosing to put in place flood proofing measures to protect some of them. This decision would constitute a proactive approach to territorial safety, which is consistent with the principles stated by the regulation ISO 31000; if applied, these principles are able to improve efficiency, effectiveness and efficacy in “disaster” risk management. The growing dissemination of temporary flood proofing techniques, the use of which draws upon the same inputs as permanent techniques, is both our easiest step

17Moreover: “Closer integration of disaster risk management and climate change adaptation, along with the incorporation of both into local, sub-national, national, and international development policies and practices, could provide beneﬁts at all scales (high agreement, medium evidence). Addressing social welfare, quality of life, infrastructure, and livelihoods, and incorporating a multi-hazards approach into planning and action for disasters in the short term, facilitates adaptation to climate extremes in the longer term [...]” (IPCC 2012). 7.5 Insurance Discount, Premium Reduction and Tax Handle 103 towards a real, quantitatively measurable leap in reducing the risk, as well as in many cases a transitional step which can be taken with many synergies to have territorial assets made permanently safer.

7.5 Insurance Discount, Premium Reduction and Tax Handle

Temporary flood proofing techniques would also contemplate some protection alternatives that may integrate different solutions to pursue objectives of local resilience; for example, some insurance tools are expressly dedicated to cover flood-related damage—not to be confused with property floods caused by plumbing breakdowns—whereas some weather financial derivatives depend on more or less complex rain or water level indexes (Gropello and Gionta 2004; Monti et al. 2009). The options of flood disaster risk treatment (shown in Table 7.5) available to a decision maker (who is unable to opt, or, in any case, who decides not to opt for permanent risk reduction measures, either on a large or on a local scale, in this second case by means of permanent flood proofing techniques), are split between what is still (or residually) ‘physically manageable’ in real time and what is ‘transferred’, being unaffordable for decision makers alone, to financial markets through insurance contracts—in their turn often covered by reinsurance contracts. Finally, after the necessary risk analysis, only the part regarding the option of retaining by informed decision (Chmutina et al. 2014) has not been ‘covered’—namely not faced by using any of the two mentioned strategies. However, here we would especially like to underline how insurance regulations on refunding flood-related damage could be economically more sustainable and favourable—whether they are based on private, public or mixed systems, both for the community and for individuals—if floods could be less destructive when hitting lands. A widespread use of temporary flood proofing techniques in urbanised lands could then make it possible to trigger a virtuous circle through the possible combination with insurance tools, since well-structured policies may encourage the use of flood-proofing techniques. Thus, insurance tools may be less onerous and, through the convergence of the two strategies, they may obtain a long-term reduction of the

Table 7.5 Schematic synthesis of the hydraulic risk treatment options Flood risk treatment options Retaining by Temporary risk Insurance informed Permanent risk reduction measures reduction measures contracts decision Large scale Local scale (Perma- Physically man- Not physically Not physically flood control nent public/private and ageable in real time manageable, manageable (public Small permanent (Temporary Flood but economi- and economi- Structural Flood proofing proofing cally cally not measures) techniques) techniques) transferable transferable 104 7 Flood Proofing Methods negative effects of hydrological disasters while protecting the community heritage and assets, thus also ensuring more economic stability. Such tendencies to a combined protection against disaster effects puts into practice the wishes of the European Commission, when stating: “in hazard-prone areas, property owners will have to invest even more in property-risk reduction measures” (EC 2013).18 In too many countries, not only in the European Union, today people do not compensate for the risk they produce by living in exposed areas. Consequently, The EU poses many questions concerning the adequacy and availability of suitable disaster insurance in the European Union, including: “Could risk-based pricing motivate consumers and insurers to take risk reduction and management measures? [...] Do insurers in general adequately adjust premiums following the implementation of risk prevention measures?” (EC 2013). The possi- bilities of combining the use of temporary flood proofing techniques with well-reasoned insurance provides for quite an encouraging answer. If, with equal floods, e.g. in terms of water height, the eventual damage is reduced by the implementation of temporary flood proofing techniques, insurers shall reim- burse lower amounts for the accidents. As a result, they could consider whether or not to ask for lower yearly premiums from policyholders. These simple remarks can bring about a few more considerations. As we will better see in the next chapter, temporary flood proofing techniques can be applied, possibly in a knowingly integrated and coordinated way, both by the community as a whole—intended as a neighbourhood, an individual administration and an associated group of administrations—and by individual property owners or managers from a perspective of economic and operational effectiveness. In this way their application contributes to the success of urbanized lands in building resilience—both from the point of view of adaptive capacity and response preparedness—on the basis of a combined set of strategies founded on the flexibility and the inclusiveness of defence systems at the individual, household and community levels (Wamsler and Brink 2014). An additional consideration envisages another modern approach to disaster protection, an approach that is made possible by the widespread use of temporary flood proofing techniques. Insurance companies and suppliers of protection equipment that abide by temporary flood proofing methods could set up operations by way of service contracts towards the installation of temporary protections, following the example of private security companies that provide inspection and guard services in public and private buildings. This approach would also solve the problem of buildings unattended for long periods every year—e.g. holiday resort homes. If coordinated with policy contracts, this option would entail a loss reduction and therefore a lower chance of maximum expected loss for the companies, at the same time generating quality jobs as this would require high-level technical skills.

18Green Paper on the insurance of natural and man-made disasters, Strasbourg, 16/04/2013. 7.5 Insurance Discount, Premium Reduction and Tax Handle 105

To encourage the spread of complementary operations joining insurance solutions and the use of temporary flood proofing techniques, it should also be considered that local and national administrations might be interested in drawing upon tax handle. By foregoing a part of potential revenue that is currently uncollected—since today these policies are not or scantily on the market—administrations would acquire lands with less losses and therefore be able to recover more quickly from flood- related damages. At the same time, other than loss of life, injuries, loss of memora- bilia and psychological distress, states would reduce losses caused by: direct damage, owing to water pressure against private structures—damage to private buildings and contents; business interruption inside the flooded area; clean up costs; direct damage to their structures—e.g. schools, public offices, cultural heritage, roads, etc.—as well as the expenses for evacuation and rescue measures; indirect damage, both tangible—disruption of public services outside the flooded area; induced production losses to companies outside the flooded area; loss of tax revenue due to migration of companies in the aftermath of floods—and intangible—trauma or loss of trust in authorities (Merz et al. 2010). As many countries provide for tax relief in respect of some insurances, it could be the same for measures ‘protecting’ heritage instead of just ‘refunding’ it, as occurs with temporary flood proofing operations (Lamond and Proverbs 2008). Outside Europe it is interesting, as an example, the case of Calgary. Indeed, after the largest flood in Alberta history, in 2013 in the new designated flood fringe zones, homeowners must floodproof if they want to obtain governmental aid after future floods. The provincial government says it will help people rebuild or repair only this last time, except the cases that homeowners who live in flood fringe zones have taken also appropriate precautions and not just refurbished the properties. Logically, at the same time, authorities announced (as in many other countries) the ban of new development in floodways—the areas subjected to the most destructive flows in the so-called ‘100-year floods’. To sum up, the implementation of temporary flood proofing techniques, which we will see as extensively possible only in a framework of emergency planning integrated by appropriate warning or alert measures, should be deemed as the contribution to a wider, all-round defense strategy to be deployed together with long period structural measures for flood control, permanent flood proofing techniques and possible insurance or mutual forms of preventive reserve of resources, in order to cover inevitable damage, at least partially. In extant literature, a similar approach (but considered from a geographical point of view) has been recently identified as Multilayered Safety (MLS) in flood risk management (Hoss et al. 2013). In our work, the more or less dominant role of all various options is determined by reasoning on the effective resource allocation, with regard to the protection targets that are set and/or actually attainable. In any case, there is no doubt that among such options, temporary flood proofing techniques will play an always greater and greater role as urban safety layer. 106 7 Flood Proofing Methods

References

Alexander D (2002) From civil defence to civil protection – and back again. Disaster Prev Manage 11(3):209–213. https://doi.org/10.1108/09653560210435803 Alfieri L, Feyen L, Di Baldassarre G (2016) Increasing flood risk under climate change: a pan- European assessment of the benefits of four adaptation strategies. Clim Change 136:507–521. https://doi.org/10.1007/s10584-016-1641-1 Aoki Y, Yoshizawa A, Taminato T (2016) 15th International scientific conference “Underground urbanisation as a prerequisite for sustainable development. Anti-inundation measures for underground stations of Tokyo Metro, Elsevier, 2016. Proc Eng 165:2–10 Barredo JI (2009) Normalised flood losses in Europe: 1970–2006. Nat Hazards Earth Syst Sci 9: 97–104 Bignami DF (2010) Protezione civile e riduzione del rischio disastri. Maggioli, Sant’Arcangelo di Romagna Bignami DF (2014) Towards a territorial multi-disaster buildings’ resistance certification. SpringerBriefs in environmental science. Springer, Milan. ISBN: 978-88-470-5223-9 Bignami DF, Biagi E (2018) Flood resilient districts: integrating expert and community knowledge in Genoa, pp 257–265. In: Smart, resilient and transition cities – emerging approaches and tools for a climate-sensitive urban development, 1st edn. Elsevier, 320 p. ISBN: 9780128114773 Birkmann J, von Teichman K (2010) Integrating disaster risk reduction and climate change adaptation: key challenges – scales, knowledge, and norms. Sustain Sci 5(2):171–184. https://doi.org/ 10.1007/s11625-010-0108-y Blöschl G, Gaál L, Hall J, Kiss A, Komma J, Nester T, Parajka J, Perdigão RAP, Plavcová L, Rogger M, Salinas JL, Viglione A (2015) Increasing river floods: fiction or reality? WIREs Water 2:329–344. https://doi.org/10.1002/wat2.1079 Bocchiola D, Rosso R (2006) Convivere con rischio inondazione: un’introduzione alle tecniche anti-inondazione. Il progetto sostenibile 9 Brugmann J (2012) Financing the resilient city. Environ Urban 24(1):215–232. https://doi.org/10. 1177/0956247812437130 Chmutina K, Bosher L, Coaffee J, Rowlands R (2014) Towards integrated security and resilience framework: a tool for decision-makers. In: 4th International conference on building resilience, building resilience 2014, 8–10 September 2014, Salford Quays. Proc Econ Financ 18:25–32 Chou J, Wu J (2014) Success factors of enhanced disaster resilience in urban community. Nat Hazards 74:661–686 Di Gropello G, Gionta G (2004) Manuale di riassicurazione, Lint Editoriale, ISBN: 888190201X EC – European Commission (2013) Green paper on the insurance of natural and man-made disasters. Strasbourg. COM 213 final, 16 Apr 2013 EEA, European Environment Agency (2012) Climate change, impacts and vulnerability in Europe. An indicator-based report. EEA report no 12/2012. ISSN: 1725-9177 FEMA (2007) FEMA 543, Design Guide Risk Management Series FEMA (2012) Principles and practices for retrofitting flood-prone residential structures, 3rd edn. FEMA, p 259 Fournier M, Blas M (ed) (2012) Référentiel de travaux de prévention du risque d’inondation dans l’habitat existant, Ministère de l’égalité des Territoires et du Logement Ministère de l’écologie, du Développement durable et de l’énergie, Republique Française. http://www.cohesion- territoires.gouv.fr/inondations Fournier d’Albe EM (1979) Objectives of volcanic monitoring and prediction. J Geol Soc Lond 136:321–326 Grothmann T, Reusswig F (2006) People at risk of flooding: why some residents take precautionary action while others do not. Nat Hazards 38:101. https://doi.org/10.1007/s11069-005-8604-6 Guha-Sapir D, Hoyois P, Wallemacq P, Below R (2016) Annual disaster statistical review 2016 – the numbers and trends. Centre for Research on the Epidemiology of Disasters (CRED) Institute of Health and Society (IRSS) Université catholique de Louvain, Brussels References 107

Hoss F, Jonkman SN, Maaskant B (2013) A comprehensive assessment of multilayered safety in flood risk management – the case study of Dordrecht. IAHS, Tokyo, p 357 IPCC (2012) Managing the risks of extreme events and disasters to advance climate change adaptation. In: Field CB, Barros V, Stocker TF, Qin D, Dokken DJ, Ebi KL, Mastrandrea MD, Mach KJ, Plattner G-K, Allen SK, Tignor M, Midgley PM (eds) A special report of working groups I and II of the intergovernmental panel on climate change. Cambridge University Press, Cam- bridge, 582 p Klein RJT, Nicholls RJ, Thomalla F (2003) Resilience to natural hazards: how useful is this concept? Environ Hazards 5:35–45 Koekoek MJ (2010) Connecting modular floating structures: a general survey and structural design of a modular floating pavillon. http://eproofing.springer.com/books_v2/index.php?token= EsEO1jrCYWkxR8KdVGdT21-hbJ1WBcto Lamond J, Proverbs D (2008) Flood insurance in the UK: a survey of the experience of floodplain residents. In: Proverbs D, Brebbia C, Penning-Rowsell E (eds) Flood recovery, innovation and response. WIT Press, Southampton, pp 325–334. ISBN: 9781845641320. Available from: http://eprints.uwe.ac.uk/16531 Ligurian Basin Authority (2005) (Autorità di Bacino di Rilievo Regionale), Criteri per la defi- nizione degli ambiti normativi delle fasce di inondabilità in funzione di tiranti idrici e velocità di scorrimento, Allegato 1 alla DGR 250/2005 Lugeri N, Kundzewicz Z, Genovese E, Hochrainer-Stigler S, Radziejewski M (2010) River flood risk and adaptation in Europe – assessment of the present status. Mitig Adapt Strateg Glob Change 15:621–639. https://doi.org/10.1007/s11027-009-9211-8 Merz B, Kreibich H, Schwarze R, Thieken A (2010) Assessment of economic flood damage (Review article). Nat Hazards Earth Syst Sci 10:1697–1724 MM Council (2016) An addendum to the white paper for developing pre-disaster resilience based on public and private incentivization. Multihazard Mitigation Council & Council on Finance, Insurance and Real Estate, National Institute of Building Sciences, Washington, DC Monti A, Hastings W, Envt’l LNJ, Pol’y (2009) Climate change and weather-related disasters: what role for insurance, reinsurance and financial sectors. HeinOnline Ogunyoye F, Stevens R Underwood S (2011) Temporary and demountable flood protection guide. Environment Agency, Bristol. ISBN: 978-1-84911-225-3. http://evidence.environment/agency. gov.uk/FCERM/Libraries/FCERM_Project_Documents/flood_protection_guide.sflb.ashx Palliyaguru R, Amaratunga D, Baldry D (2014) Constructing a holistic approach to disaster risk reduction: the significance of focusing on vulnerability reduction. Disasters 38(1):45–61 Pine J (2015) Hazards analysis. CRC Press, Boca Raton. ISBN: 9781482228922 Pine J, Guillot SL (2015) Risk communication. In: Pine J (ed) Hazards analysis. CRC Press, Boca Raton. ISBN: 9781482228922 Programmes d’action de prévention des inondations (PAPI) (2010) De la stratégie aux programmes d’action – Cahier des charges. Ministère de l’Écologie, du Développement durable, des Trans- ports et du Logement. www.developpement-durable.gouv.fr Quade D, Lawrence J (2011) Vulnerability and adaptation to increased flood risk with climate change—Hutt Valley household survey, report 06 October 2011. The New Zealand Climate Change Research Institute – NZCCRI, Victoria University of Wellington Santato S, Bender S, Schaller M (2013) The European floods directive and opportunities offered by land use planning. CSC report 12, Climate Service Center, Germany UNESCO (2001) Guidelines on non-structural measures in urban flood management UNISDR Annual Report (2015) 2014–15 Biennium Work Programme Final Report, United Nations Office for Desaster Risk Reduction (UNISDR) 9-11 Rue de Varembé, 1202 Geneva, Switzerland USACE (1995) Flood proofing regulations. U.S. Army Corps of Engineers, Washington, DC 20314-1000. EP 1165-2-314 108 7 Flood Proofing Methods

Wamsler C, Brink E (2014) Moving beyond short-term coping and adaptation. Environ Urban 26(1):86–111. https://doi.org/10.1177/0956247813516061 Werrity A, Houston D, Ball T, Tavendale A, Black AR (2007) Exploring the social impacts of flood risk and flooding in Scotland. Social Research Environment Group, University of Dundee White I, Connelly A, Garvin S, Lawson N, O’Hare P (2016) Flood resilience technology in Europe: identifying barriers and co-producing best practice. J Flood Risk Manage. https://doi.org/10. 1111/jfr3.12239 Chapter 8 Temporary Flood Proofing Techniques Planning

Despite the generosity of public special forces and the passion of volunteers, the necessary and timely action during a flood event requires collaborative joint and coordinated technical efforts, especially when the population is involved; yet this is currently achieved in very few places throughout the world. This much needed communal effort does not occur in spite of a number of complex regulations which are already applicable in many countries, above all in the most advanced ones, notwithstanding the increasingly widespread economic problems and the sometimes correlated frequent delays of economic public intervention in supporting the ‘post-event’ restoration of normal life conditions in disaster-stricken areas; these areas, consequently, need and ask the decision-makers to provide additional on-time-readiness. Such situations should be enhanced by improved preparedness for coping with disasters and averting damage, on account of the difficult reparability of possible flood events, which does not exclusively concern merely economic issues, but also social, environmental as well as historical and artistic protection.

8.1 Approach to Arrangement and Activation

After considering the strategic planning of flood risk reduction measures through flood proofing techniques—see previous chapter—according to the technical assessments they will be provided with, decision makers will define the risk reduction objectives that they wish to pursue through the different possible operations based on every viable temporary—rather than permanent—flood proofing techniques. These should be organized rationally in a relevant systematic document which should be part of the local emergency planning, in order to link the operations to other provisions contained therein. In regard to creating defensive measures out of evidence from warning and territorial surveillance activities on hydraulic risk by different sections of civil protection services, temporary flood proofing techniques can ensure good services,

© Springer Nature Switzerland AG 2019 109 D. F. Bignami et al., Flood Proofing in Urban Areas, https://doi.org/10.1007/978-3-030-05934-7_8 110 8 Temporary Flood Proofing Techniques Planning which we are going to analyse in this chapter on a case-by-case basis. Good services, especially, if compared to the often-deceiving situations produced by current performance of emergency measures, which shows a lack of resources and, particularly, of operational alternatives, however these could be undertaken by motivated personnel. The already improved capabilities of risk identification and event forecasting, though often improvable, are not enough to avoid damage if they do not give rise to tangible and timely actions. As Sir John Keegan—British military historian, 1934–2012—wrote in his book “Intelligence in War”1 in 2003: A wise opinion would be that intelligence, while generally necessary, is not a sufficient means to victory. [...] Intelligence is only as good as the use made of it [...] War is not an intellectual activity but a brutally physical one, Similarly, we could argue that, since water action can be equally brutal, unfortu- nately, monitoring, surveillance and advance warning—our field ‘intelligence’ of civil protection operations—are not enough to protect urbanized lands from floods. In order to obtain significant results and reduce losses, it is essential to better exploit collected data being prompt by either physically avoiding water action or opposing its energy. Within this framework, temporary flood proofing techniques should be cautiously approached to tap their full potential, since they are one means to possibly achieving slightly better results in countering floods. Obviously, the various techniques do not differ only in the mechanisms chosen to offset floods, but also in the way of their use, as mentioned in the previous chapter, following an increasingly high number of factors that reflect the developed techniques available on the market. On one hand, some factors or characteristics influencing the use of flood proofing techniques may be understood in a sufficiently intuitive manner. On the other hand, some others need to be briefly shared, namely some illustrative and interpretative schemes of the sequential dynamics of risk reduction real-time action which is performed in civil protection operations during a flooding, plus some basic use patterns of temporary flood proofing techniques. Choosing a risk reduction strategy based on temporary flood proofing means making use of a great deal of potential which might be offered by different types of know-how and skills of disaster risk management: designing tools—industrial, too—reconstructing scenarios, promptly collecting essential information, planning complex safety measures, mastering operational methods and techniques, being prepared to cope with inevitable and unexpected events. As with the most advanced search and rescue operations, such knowledge requires a tight inter- weaving of decisions and measures to be adopted long before the events, when

1“Intelligence in War: Knowledge of the Enemy from Napoleon to Al-Qaeda”, by John Keegan, Alfred A. Knopf Publ., New York, 2003. 8.2 Decision Factors: The SENSO Model 111 they are about to come and when they occur.2 All EU countries should consider these in Flood risk management plans as provided for by the aforementioned Directive 2007/60/EC.3 After the references of a general discussion, in this chapter and in the following one, going into those factors which influence the choice of temporary flood proofing techniques and a description—broadly formulated, yet not comprehensive—of the most widely shared and interesting floodproofing approach and techniques, we will offer a new reasoned interpretation scheme of the way of using temporary flood proofing techniques which might be of practical use for both planning operational solutions with regard to real-time defense against floods and as support and reference for research and development focusing on the investigation and modeling of flooded surfaces at increasingly detailed scales.

8.2 Decision Factors: The SENSO Model

As anticipated, many factors need to be evaluated to make the right choice among temporary flood proofing techniques. An accurate considering of such factors along appropriate lines is necessary to identify the most suitable technique—or combination—to be used in the territorial context being protected. This is why we suggest a logical organisation which may allow for a rational selection, as happens today for other types of functional choices applied to buildings or blocks about desired performance, e.g. concerning heating and cooling in terms of energy saving, brightness and healthiness of indoor environments, liveability in public open spaces, intrusion security and so on. For this purpose, we developed a decision scheme model: the proposed model was called “SENSO—Socio-economic context, ENvironment and event Scenarios, field Operations”. Factors can be sorted into groups referring to each of these three domains: the socio-economic context which temporary flood proofing techniques shall be applied to; the environment in which they shall be implemented, strictly connected with the event scenarios; the characteristics of necessary or possible field operations to opt for different solutions. Once the implementation framework through the SENSO model is defined, decision makers will find it quicker to make their choices in respect of the use of different temporary flood proofing techniques.

2In addition to what we already recalled in the previous chapter, according to ISO standard 31000, since 2009 (2018 second edition) risk management should be: systematic, structured and timely (comprehensive); based on the best available information; tailored (customized) on the basis of context and risk profile; taking human and cultural factors into account; dynamic, iterative and responsive to change. 3In Italy, for instance, all such decisions should entail the professional and operational growth of territorial protection activities in accordance with Prime Minister Directive of 27 February 2004 on the national warning system for flood and landslide risks. Indeed, this is how we could envisage the best possible cooperation and operational synergy. 112 8 Temporary Flood Proofing Techniques Planning

The first group of factors being taken into consideration by the SENSO model and described in the next paragraphs are those pertaining to the reference Socio- economic context; this mostly take into account resources which are effectively usable for the protection strategy, particularly regarding: I. (C1) Available budget with regards to the area being protected; II. (C2) Availability of trained workforce and/or possible self-employment for private individuals; III. (C3) Availability of suitable means of transport and auxiliary equipment for operational purposes. Then, the factors contemplated in the SENSO model to make the best choice among temporary flood proofing techniques in respect of the reference Environment and event scenarios allow selecting techniques on the basis of the physical-natural and anthropic conditions of the areas being protected, via the assessment of: IV. (E1) Solution performances in relation to water level h, flow velocity v and solid transport values—i.e. in relation to the different event scenarios which may occur; V. (E2) Extension and type of span (or spans) being protected; VI. (E3) Need for preliminary studies and site preparation depending on detailed ground morphology; VII. (E4) Building types, ranging from foundations to construction materials, as well as urban characteristics of the constructions being protected. Lastly, another group of factors within the SENSO model that helps to distinguish among temporary flood proofing techniques on the basis of various aspects of the field operations needed to put them in place—both in terms of operational manoeuvres and logistical implications; the aspects are the following: VIII. (O1) Speed of installation and deployment according to event frequency and the time made available by the warning system, as well as to the size and weight conditions of the defense line being arranged; IX. (O2) Potential reuse and multipurpose use, in different flood events or for alternative purposes; X. (O3) Preliminary territorial equipment and possible minor requirements for territorial infrastructures or buildings to use or install the identified solutions; XI. (O4) Availability of materials and additional apparatus in case of need; XII. (O5) Removability and induced residual environmental impact at the end of the flood event; XIII. (O6) Quality and quantity of storage areas, when not in use; XIV. (O7) Maintenance requirements, operating times and potential repairs in case of damage, even when operational. The 14 decision factors assembled in the SENSO model will be the starting point for a technical and reasoned description of an inevitably partial, even though large, selection of many important temporary flood proofing techniques, which we are going to present in the next chapter. 8.3 Temporary Flood Proofing Response Planning 113

8.3 Temporary Flood Prooﬁng Response Planning

In order to fully comprehend the proposed categorisation and to better know temporary flood proofing techniques and decide for the best strategy to be adopted for defending lands from water, it is first necessary to recall and highlight some ideas as possible absolute references on time development of disasters, according to human response in adopting countermeasures. The evolution and establishment of temporary flood proofing techniques goes hand in hand with the enhancement of monitoring, forecasting and warning techniques, and their connection should be closely coordinated. Each overall strategy of disaster risk reduction requires some operations or preliminary phases: the use of temporary flood proofing techniques is no exception. Firstly, it is essential to undertake a thorough identification of potential threats which might affect a territory—namely the event scenarios. Secondly, a possible quantitative risk analysis should be performed on them in order to allow for an assessment (Cf. Pine 2015). On one hand, depending on such assessments and the available resources, it will be possible to realize how to work on factors like hazard (through prevention activities), vulnerability (through protection activities) and exposed value (through mitigation activities), whose combination provides for risk values—(see Fournier d’Albe 1979; Granger 2003; Grünthal et al. 2006; Kron 2005). On the other hand, it will be possible to determine which risk elements to handle with permanent measures and which with temporary measures—often applicable in the case of transitional periods, when permanent works are carried out. These phases should be completed within the strategic planning of flood risk reduction measures through flood proofing techniques—see previous chapter. Once the above mentioned strategic plan has been adopted, emergency planning can be elaborated and approved. One of its sections, when flood risk is the question, shall be expressly dedicated to event response by means of temporary flood proofing techniques, which we will call: Temporary flood proofing response planning. Consistently, at a later stage it will be necessary to conclude trial operations, including monitoring and warning networks, once procurement and territorial equipment actions in respect to the chosen defence apparatus are complete and the first essential staff training activities are put in place. As a whole, these make up the preparatory period for the activation of civil protection services. The end of such activities is the only key to the actual operational period, namely starting with the disaster monitoring activity which concerns professional civil protection services (Bignami 2010). To utilise temporary flood proofing techniques, procurement and territorial equipment actions are particularly important—including practice, other than training, which is always significant for each civil protection activity. As already mentioned and illustrated hereinafter, if compared with our benchmark, i.e. ‘sandbags’, all innovative 114 8 Temporary Flood Proofing Techniques Planning

flood proofing techniques do require a preliminary preparation for the intended solution, which must be supplied in advance—through purchased shared, or rental systems, procurement and so on—and, if necessary, must be ready-made in advance—installation, ground or building anchoring, modelling and/or land clean-up, etc. If the ‘sandbags’ can be deemed a resource with basically ‘infinite’ availability, suitable for ‘all purposes’ scenarios, being relatively easy to use—though preferably after appropriate training courses—and easy to find, this is not the case for the most advanced techniques of temporary flood proofing. Such availability and advantages of sandbags, however, should not result in underestimation. While in almost all cases temporary flood proofing techniques offer better performance in many respects, they demand greater organisation and preparation efforts before the events—which can be exclusively made in a very limited or planned manner during the events. These efforts are principally to be synthetized in the above introduced Temporary flood proofing response plan, which includes, among other things, sites and times of installation, selected techniques, workforce, means and ways of transport, auxiliary equipment available, etc. As already described, once the preparatory period activating the civil protection services is over, the next operational period becomes effective in a more or less long waiting period, in which civil protection services limit themselves to monitor,to organize exercises (to drill) and to perform functional maintenance on all apparatus—although these should not be undertaken in periods with higher frequency of disasters during the so-called ‘advance warnings’. When significant weather events occur, watching can trigger the so-called warning ‘sub-period’, which depending on the event dynamics—e.g. rain intensity, basin concentration and flood formation times, snow melting, etc.—can be generally divided into phases called pre-alert, alert and alarm. It is in such phases that temporary measures for risk reduction are implemented, obviously including temporary flood proofing techniques. These phases entail the eventual deployment of different types of barriers and apparatus, according to the arrangements and provisions of the Temporary flood proofing response plan. In this connection, an articulated set and control role should be played by a Temporary flood proofing special service divided into teams, each of which is responsible for the installation and/or checking on the correct arrangement of the barriers. These will be organised either on a territorial basis—e.g. a neighbourhood—or according to the degree of specialisation in operating specific equipment rather than other. The aforementioned issues can be summarized, using the disaster cycle model (Alexander 2000), as shown in Fig. 8.1, where it is possible to find the crucial operational steps for planning the use of temporary flood proofing techniques: preparation for use before going ‘on duty’ (in emergency planning) and timely deployment during a disaster (in warning phases). Additionally, it should be underlined how the figure includes permanent flood proofing techniques in risk reduction phases, which must be concluded in time in order to be corroborated in emergency planning. 8.4 Defence Lines 115

Fig. 8.1 Time frame of ﬂood prooﬁng techniques within the disaster cycle (drawing of D.F. Bignami)

8.4 Defence Lines

Another essential element influencing the choice among the available basic use patterns of temporary flood proofing techniques is the needed, preliminary positioning of water defence lines to be carried out through temporary flood proofing techniques. Such lines should be located as quickly as possible to timely anticipate any hydraulic disasters, as well as appropriately incorporation in the Temporary flood proofing response plan by using relevant schemes which we will call: Defense line maps.

8.4.1 Positioning

Not surprisingly, defense lines are firstly required to connect points whose heights are at least at the expected flood level, according to event scenarios, by means of barriers exceeding such levels at any point. To reach this goal, designers must be concerned to correctly draw up, regarding specific sections: the barrier height profiles and must check that at any point it exceeds the maximum expected flood level, obtained by applying the right safety coefficients to compensate for the stochasticity of the hydrological, morphological and human variables which may affect floods 116 8 Temporary Flood Proofing Techniques Planning

Fig. 8.2 Determination of barrier height proﬁle with regard to maximum expected ﬂood level (drawing not in scale); depending on the form and type of the supporting surface, two types of barriers are represented

(in particular, in the likely event of agitated water surfaces, flood levels need to be overestimated to obtain the necessary correct freeboard). Such configuration is illustrated in Fig. 8.2. According to the importance of the defense line and available resources, the positioning could take place by using the information obtained from the Digital Elevation Model—DEM, and/or through field topographic tools during specific—yet essential—inspections. Ideally, this should happen with reference to high-detailed maps (at least 1:1000). As chosen by the designer, the positioning of defense lines decisively affects the resulting water heights. For this reason, it is useful to bear in mind that possible positioning types of defense lines4 can be classified according to the action they can ensure in pursuing risk reduction objectives: • ‘Advanced’ or ‘Outer’ line, namely very close to or opposite the source of threat—e.g. watercourse or lake embankments—in order to protect the whole ‘sheltered’ land (for this reason it is also called ‘areal’); • ‘Intermediate/Middle’, ‘block’ or ‘deflection’ line, if it does not prevent water from overtopping levees or embankments but protects only portions of land being either strategic or considered of overriding importance—or sometimes easier to protect, as far as detailed altimetry is concerned; this line too is often considerable acting as ‘areal’, other times as ‘sub-areal’ or ‘selective’ (when defending only the most relevant exposed goods); • ‘Inner’ line, if it focuses only on protecting individual buildings and lets water invade the remaining land; this line can also be conceived as a closed ring—particularly, in the cases of closed floodwalls and dry flood proofing (in this case this type of line is also called ‘single building’).

4The names of the possible types of defence lines have been coherently chosen having also in mind the ﬁrst results of the exchange of best practices in the approaches to address common vulnerabilities and climate change risks, downscaling the outcomes from a regional to a local level. See for instance Piet Dircke at “NAP Expo 2015: Realizing the NAP process, Bonn, 14–15 April 2015” (Dircke 2015). 8.4 Defence Lines 117

The first one and the second one, being ‘areal’, are not always easy to put in place, being strongly influenced by the morphology of the sites. However they are often very functional in contexts characterized by altimetric variations. The third, also called ‘single building’, is almost always possible to be deployed and is often the most useful in plain urbanized areas, where deflecting water expansion is a difficult task. In the first case, the advanced line will act by specifically reducing the hazard—trying to counter the flooding; in the third case, the inner line will focus on reducing vulnerability—trying to avert damage once the flood has struck. The second case is clearly halfway between the two others. According to these categories, the choice of the best defense line should take different contextual factors into account, as mentioned at the beginning of the chapter. It will certainly have a decisive impact on the choice of temporary flood proofing techniques, because some of their actions are specially conceived to match only with certain types of defense lines. The joint effort should be adjusted on available resources, proportionally to the significance of land and goods being protected, and could be subject to technical or morphological restrictions. Thus, in most complex cases, to rightly position defense lines, it should first be useful to mark preliminary defence lines, to select alternatives to be assessed during the design workflow. As an example, the water height and related stream flow near a levee could require the use of ‘weighty’ temporary flood proofing techniques that cannot be deployed on a long levee section in due time, owing to the time interval given by the available forecasting system and, perhaps, also because they are too onerous or demanding if compared to the targets being protected. In that case, it could be wiser to protect individual targets, with the advantage of leaving land (almost) ‘naturally free’ to store part of the flood volumes—benefiting downstream lands, too, which would encounter a less severe flood. Moreover, defending a levee which flanks and protects a roadway could mean preserving a vital way of communication and not leaving population centres isolated. Any decisions should therefore be made by civil protection authorities5 and decision makers, on the basis of assessed and chosen strategies, and provided as detailed input to designers. Figures 8.3 and 8.4 show a schematisation of defense line positioning within a (simplified) hypothetical territorial context being protected. Furthermore, an additional strategy is possible, or sometimes necessary, given the uncertainty of event scenarios which might take place, or given the complex varying altimetry or mountainsides in some situations. It consists of positioning a specific number of consecutive defense lines (making a sort of flood defence corridors or

5In Italy, such decisions should be incorporated in the plan section called ‘planning outline’, according to the Augustus Method (DPC 1997), or ‘planning outline and operational strategy’ in 2007 Operation Manual (DPC 2007). 118 8 Temporary Flood Prooﬁng Techniques Planning

Fig. 8.3 Hypothetical territorial context being protected through temporary flood proofing techniques and possible scenario of levee-overtopping flood (drawing not in scale) cells), which can be defined as multiple defense lines, either when water tightening provided by advanced defense lines is supposed to only be partially effective and inner lines alone are unable to bear the consequences of the whole event, or when pressurised water can force floodways and drainage pipes and channels to reverse, circumventing the defence line and ‘take it’ in rear.

8.4.2 Water Reaction Assessment and Connected New Flood Prone Areas

It is also important to emphasise that the positioning of a defence line will generate a new territorial element that will change the natural trend of water distribution on the free, i.e. defenceless, surfaces which may be located beneath the new open water height produced by, for instance, the position of temporary dikes—in other words, ﬂood volumes that will not undergo lamination due to the fact that such line will be affecting other sites, for which it should also be assessed whether they need or deserve to be protected, if assuming a unitary logic. Hence, the main or primary defense line may require complementary/additional/supplementary or secondary 8.4 Defence Lines 119

Fig. 8.4 Defence line options: 1—Advanced or Outer line; 2—Intermediate/Middle line; 3—Inner line (drawing not in scale) defense lines, whose presence is made necessary because of the existence of the main/primary ones, in order to offset water ‘reaction’ following the unpredicted obstacle to its natural outflow—clearly enough, all primary and secondary lines could be multiple lines, too (with the goal to reach higher safety levels thanks to this redundancy). In addition, it should be pointed out that, obviously, both primary and secondary lines can be advanced, intermediate and inner lines. Figure 8.5 illustrates land positioning of main (primary) and complementary (secondary) defense lines within a hypothetical territorial context being protected. As far as land and urban planning is concerned, the above situation is especially significant for giving rise to the consideration of the reliability of flood-prone areas and connected authorised land use. Flood proofing techniques can be used to protect ill-advisedly urbanized lands, even though, for instance, no abuse might have occurred because structures had been erected before regulations on floodplain occupation were approved. In such cases, not only could the above situation take place for the implementation of complementary/additional/supplementary defence lines, but these could also be arranged for sites which would lie outside the limits of land use in cases of flooding (occurring without an upstream main defence line), thus generating quite a thorny situation if such areas would in future be developed rather than remaining free. In these cases, safeguard measures, connected with the land for the positioning of temporary flood proofing techniques, could be required. 120 8 Temporary Flood Proofing Techniques Planning

Fig. 8.5 (A) Naturally ﬂooded areas—hypothetical event scenario; (B) Flooded areas induced by positioning a main defense line; (C) Flooded areas induced by positioning a complementary/ additional/supplementary defense line (drawing not in scale)

8.4.3 Deployment

When positioning a defense line, some additional elements expressly regarding its deployment must be taken into account. From a geometric point of view, when positioning a defense line, it should first be remembered that its direct and induced surface areas must not be underestimated. The former, i.e. direct surface area, is related to the actual ‘footprint’ of the defensive apparatus on the ground, including any support sealing equipment. In regards to the intended line for holding back water, specifically the actual defence ‘line’, it is therefore necessary to draw the following elements in an appropriate scale on a map updated on the real conditions of the sites, whose relief shall be period- ically updated: one front edge and one back edge, which are essential to assess the actual overall surfaces areas of the temporary flood proofing equipment designated for operations, in order to assess their effective usability with regard to possible land obstacles—trees, boulders, poles, benches, low walls, pavement, manhole covers, etc.—and design their specific use, however hastily it is done. In fact, the defense line is not one-dimensional line, but a two-dimensional zone (like a sort of stripe) with a non-neglectable surface area comparable to a footprint—being the defence line included in, as it is the limit reachable by the rising water. Some techniques demand another geometric assessment of direct surface area. In such cases, the shape and size of each module (both horizontally and vertically) are assessed, yet some of them, due to other modules, may not be ‘flexible’ or ‘small’ 8.4 Defence Lines 121

Fig. 8.6 Direct (actual footprint) and induced (precaution zone) surface areas of a defense line (drawing not in scale) enough to fit and to be used through all degrees of freedom of movement (3D) which are normally allowed on a free plane, since they may be subjected to relative restrictions in order to ensure the line’s general tightness. The latter, i.e. induced surface area, is related to the establishment of a necessary “hindmost line” on the side opposite to the water, aiming at outlining a protection and precautionary evacuation zone behind the defense line. During floods, such zones are often put in place even in conjunction with permanent levees. Their ‘depth’ or distance from the defense line is included in, or corresponds to, the estimated limit of natural water expansion without any defence line. Figures 8.6 and 8.7 illustrate the geometric surface area of defense lines based on temporary flood proofing techniques and the overall shapes of individual pieces of equipment. Finally, a proposed basic check-list to assess any defense line6 to be deployed on the ground (and included into the Temporary flood proofing response planning) should always include, after the evaluation of direct and induced surface areas, additional criticalities that every project designer should take into account:

6Note that here we are treating about a defense line, not a single kind of flood proofing technique, a defense line being potentially composed by several different kind of techniques. 122 8 Temporary Flood Proofing Techniques Planning

Fig. 8.7 Horizontal (plan) geometric shapes of individual ‘sections’ or modules combined into various defense lines. The shape on the left cannot complete the curve or ﬁt into the space made available by the building (the apparatus not being ﬁtting nor overlayable); the one on the right succeeds by changing techniques for the curve (drawing not in scale)

– ‘Weightiness’ of the chosen technique with regards to flow velocity and transported materials. For instance, some temporary flood proofing techniques cannot withstand the pressure or the flow of a torrent during flooding, or when being struck by tree trunks, furniture or garbage containers—not to mention vehicles—in the same way they can offer different response to low rising lake water levels; – Support base geometry: flat, smooth, asphalted surfaces or grasslands are the optimum support base for a defense line, unlike sloping, curved or stooped grounds—or uneven pavements, traffic islands, parapets, rails and so on. In these conditions, the establishment of defense lines becomes much more complicated and sometimes cannot be achieved. – Promptness in moving mobile obstacles: vehicles, waste containers, dumpsters, mobile street furniture in general, gazebos, and so on, must be timely removed to allow the positioning of the defense lines (and to avoid the possibility of water pressure and flow that can push them against the defense lines themselves). – Discontinuities: for reasons related to the establishment of the defense line it might be necessary to employ different techniques at the same time, placed side by side, because a change in the ground surface (such as asphalt changing into sandy ground, the two having different permeability). Such points of discontinu- ity or juncture should be avoided as much as possible. If they cannot be avoided, special attention must be paid to their implementation since they can be regarded as a potential ‘weak point’ of the line—, situations that not always are included in the solutions provided by the equipment manufacturers (because the large number of cases). Similarly, sudden shifts in direction, e.g. when right-angled junctions are required, may turn into less advantageous situations as to flood proofing action, depending on the technique; understandably, this criticality is more important for advanced and intermediate defense lines (the areal ones) since, as it will be better shown in the next chapter, often it is less severe in single buildings, when using some pre-arranged/pre-located or demountable temporary flood proofing solutions. 8.4 Defence Lines 123

– End connections: like in the previous case, they constitute a potential ‘weak point’ of the whole line, as they definitely need to be implemented ‘on-site’ depending on actual conditions, which sometimes are unpredictable or cannot be controlled beforehand, and are often ‘under pressure’; as before this criticality too is growingly important for advanced and intermediate defense lines. – Accessibility, on-site surveillance and impact on mobility and public services: another operational aspect that deserves consideration in the design phase is the promotion of the fastest and most protected line supervision by authorised personnel during the events, so that they can intervene—e.g. for either reparation purposes or monitoring to warn about potential overtopping or line breaks. Locations which are inaccessible (during the flood, due to the raising water) or too large to be controlled with the available personnel can result in insufficient surveillance and originate severe accidents (in case of embankment failure, collapse or overtopping); sometimes, in case of large inundations, even access roads to the defense lines that are available for deployment could be interrupted; in case of such critical scenarios, more prompt action has to be considered, so as to assess the redundancies of access ways, until line positioning is reconsidered. – Needs of water-scooping (draining) pumps (machines): when the situation is critical and it may be necessary to integrate or complement the action of the defense lines. – Additional steps of preparation to prevent back-flow of floodwater through plumbing or drainage systems (public or private sewer, inside or outside buildings): during a flood sewer can be a preferential way of water circulation beyond the positioned barriers on the ground, due to the Archimedes’ principle effect (see Fig. 8.8); the disregard of this aspect of the connection of “ground and underground” waters could result in a failure of your defensive scheme.

Fig. 8.8 The back-ﬂow effect scheme that is to be prevented 124 8 Temporary Flood Prooﬁng Techniques Planning

Fig. 8.9 Temporary ﬂood prooﬁng comprehensive logical scheme

8.4.4 Comprehensive Logical Scheme for the Use of Temporary Flood Prooﬁng

To summarize different phases enabling the most suitable use of temporary flood proofing techniques, the following figure shows the logical scheme elaborated to recapitulate and help in fixing the described path of previous paragraphs (Fig. 8.9).

8.5 A Notable Requirement Case: Pisa (Italy)—Or Where, Probably, the Modern Temporary Flood Prooﬁng Was Started

The town of Pisa is situated very close to the Mediterranean coast of Tuscany and is crossed by the river Arno. In the year 1966, Pisa was hit by a huge flood—the same destructive flood that simultaneously struck Florence. Since then, to protect the town and the historical city centre, which is very rich in artistic treasures, the construction of an important floodway has been completed (although the possible role of a hydraulic construction such as this had been considered of crucial importance for 8.5 A Notable Requirement Case: Pisa (Italy)—Or Where, Probably... 125 the flood defence of the city since the end of the Second World War, when it was only a project): the spillway canal that is located upstream from the town, not far beyond the small town of Pontedera, can deviate, today, a volume of water up to 600 m3/s (although it theoretically could reach a capacity of 1400 m3/s—a capacity it cannot today achieve due to problems of sand accumulation at the mouth of the river). Long before that, however, in 1920, the strategy against floods had started and was based on another typology of defence: that is the positioning, when substantial flood flows were expected, of wooden flood gates all along the riverbanks of the historical city centre (Fig. 8.10a, b). In all probability, Pisa’s wooden flood gates can be claimed to mark the date of start of modern techniques of temporary flood proofing (incidentally, the centenary of the wooden gates introduction is now near). The system, based on wooden gates put in place only when necessary, is still in use today, precisely to integrate the defense provided by the deviation of water supplied by the spillway canal. The efficacy of defences put in place in Pisa in 2014, both the action of the derivation of the Arno river discharge and wooden flood gates, is proved by an estimation of the damages avoided in Pisa, based on an urban flood damage model assuming the city with or without defences: without water diversion and flood gates damages would have amounted to 100 million euros, with them damages amounted to 0 € (Arrighi et al. 2013; Arrighi and Castelli 2014). Because of the historical interest in the wooden gates system, its relevance as far as quantitative/dimensional aspects are concerned, the strength (and stability) of its well-tested procedures (and components), we offer below a comprehensive account of an instance of temporary flood proofing technique, choosing the punctual narra- tion of the reconstruction of its most recent utilization in 2014. We do that believing that an in-depth description is altogether useful to understand the complexity of temporary flood proofing.

Fig. 8.10 Old town centre of Pisa: left—Lungarno Galileo Galilei (1920), before the introduction of flood gates; right—Lungarno Pacinotti (1947), flood gates in action (courtesy of Provincia di Pisa 2014) 126 8 Temporary Flood Proofing Techniques Planning

On Wednesday 29 January 2014, the Operations Room of the Tuscany Region issued a Level-2 weather alert for the two following days. At 2:30 a.m. of 31 January 2014, the Arno River Flood Management Service declared that the first watch status had been initiated due to raising water levels. As a result, on the same night the Emergency Rescue Coordination Centre (in Italian Centro Coordinamento Soccorsi—CCS) for the Province of Pisa convened at the Prefecture and decided to install stoplogs all along both embankments of the Arno river (“Lungarni”) throughout the old town centre of Pisa. At 5:00 a.m. the first alert threshold of 4 m above gauge datum (or zero level) was exceeded. At 5:50, while teams trained for the purpose made up of volunteers, firefighters and troops—72 soldiers from Folgore Parachute Brigade—were assembling barriers, the floodway channel was opened at a flow rate of 600 m3/s. A flood of over 2500 cubic metres per second was expected to arrive after 9 a.m. and last for some hours. At 6 o’clock on that very morning, 10 min later, 30 m of the Etruscan walls collapsed on account of heavy rains in Volterra, a town in the Province of Pisa. In the meanwhile, at 7:20, the town centre of Pisa was fully closed to traffic, 37 roadblocks were placed throughout the street network and later, at 8:40, those residents living on the ground floor within the Arno embankment areas were asked to move to upper floors or outside the “red zone” (Fig. 8.11). At 9:30 the Arno river reached 4.75 m above gauge datum, exceeding the second alert threshold of 4.70 m. At 11:10 the flood reached 4.84 m, then got as high as to a peak of 4.91 m and kept up such rate until 4:40 p.m., when it went back to 4.87 m.

Fig. 8.11 Old town centre of Pisa, the red zone alongside the Arno river (Comune di Pisa, Piano di Protezione civile 2010) 8.5 A Notable Requirement Case: Pisa (Italy)—Or Where, Probably... 127

At 8:30 p.m. the Arno river receded to 4.78 m, at midnight to 4.69 m and continued dropping. From a technical point of view, the CCS decided to position a double defense line alongside the Arno river, i.e. establishing one line on each embankment, which consisted of tar-coated wooden gates dating back to around 19207 that were placed on the left bank (Lungarno Galilei, Gambacorti and Sonnino, 1.4 km), and those made of galvanized steel shields on the right bank (Lungarno Mediceo, Pacinotti and Simonelli, 1.3 km). After being reinforced with sandbags to obtain improved weightiness for the following flood of 11 February 2014—having a lower flow rate but also an adverse sea level, thus having similar gauge heights and a peak of 4.98 as well as a floodway channel at a 400 m3/s flow rate—shields were positioned in order to raise the river embankments as an ultimate measure to avoid overflowing (Figs. 8.12, 8.13 and 8.14). Each of them was part of an advanced line following a floodwalls pre-arranged/ pre-located technique—with no closed ring—which made use of built for the purpose anchoring rings—pre-existing since 1920, when the former works were carried out—on masonry parapets of river embankments. Such anchoring occurs by means of ‘chair-shaped’ holders, which are vertical elements made of cast-iron or steel whose aim it is to secure shields together through their ‘double-C’ shape, as

Fig. 8.12 Pisa (old town centre, Lungarno Galilei), tar-coated wooden gates were placed to rise the embankments of the Arno river (winter 2014)

7Wooden gates were built during the reconstruction of the Arno parapets in the summer of 1920, following a break in 1919 and a ﬂood in 1920. Now they are only present on the left bank, on the inner downstream side of the river, where water levels and pressure are expected to be lower than on the outer side. 128 8 Temporary Flood Prooﬁng Techniques Planning

Fig. 8.13 Pisa (Lungarno Galilei), tar-coated wooden gates reinforced with sandbags were placed to rise and increase watertight seal of embankments against the incoming Arno ﬂood (picture of D.F. Bignami) well as to consolidate their connection and create a continuous line. Luckily, there was no need, just for few centimeters, for this line to function, although it was timely assembled and kept on-site until 16 March 2014—gates and shields were removed by a company assigned without emergency procedures during the nights from 17 March to 21 March—owing to a warm and rainy winter. Such anchoring needs constant maintenance and is one of the line’s criticalities in terms of stability and watertight sealing, especially due to the ‘gap’ between the gates, perpendicular to downstream, and below them. This tightness, which basically cannot be assumed, is currently excluded from the declared objectives of Pisa Civil Protection Service, as it is not essential for human safety and for protecting goods—it should also be considered that during a ﬂood event it is not important whether streets get wet. 8.5 A Notable Requirement Case: Pisa (Italy)—Or Where, Probably... 129

Fig. 8.14 Pisa (Lungarno Mediceo), assembling of metal shields (web)

End connections by means of sandbags near crossings are another criticality (Fig. 8.15). Moreover, if compared to wooden gates, metal shields do ensure height uniformity of the defense line—60 cm against variable heights of 30, 40 and 65 cm—however both lines are distinguished by their weightiness and the low manageability of identified solutions. Nonetheless, on February 13 a wooden flood gate was missing—and was then immediately replaced with another gate. Due to a prompt deployment and availability of river officers, in order to access warehouses, as well as that of operational teams and vehicles, and due to working double shifts, often performed in bad weather for such burdensome tasks, in 7 h, 3 h before the needed time to assemble the gates, Pisa Civil Protection Service has been able to install a total of 1334 gates of 2 m in length, 1287 of which were vertical elements, as well as other special components and 9156 sandbags—around 7 for each gate. These materials are stored in three warehouses that are located very close to the Arno banks (Guadolongo, Discesa Soarta and Sostegno), with double entrances enabling lorries to reduce their loading times. A total of 12 lorries are available for operations and each of them is provided with 6 operators working in shifts of 2/3 hours. First, they pick up, transport and assemble the vertical elements. Then, they pick up, transport and assemble the gates. Finally, they pick up, transport and place sandbags—which are stored already filled and are placed on pallets to facilitate their handling. 130 8 Temporary Flood Proofing Techniques Planning

Fig. 8.15 Pisa (old town centre) criticalities of defence lines: on the left (Lungarno Pacinotti), the beginning of the metal shielded line downstream of “Ponte di Mezzo” (central bridge), connected with the bank through sandbags (picture of D.F. Bignami); on the right (Lungarno Galilei), wooden gates anchored to masonry parapets and their connection (picture of D.F. Bignami); at the bottom (Lungarno Gambacorti), the missing gate on February 13 (web)

What was achieved in Pisa has certainly been an extraordinary practice of a civil protection service acting in real time by making efficient use of complex and tested solutions, according to procedures built for the purpose that are rightly connected with monitored, studied and modelled event dynamics for warning purposes. While this experience helps illustrate the feasibility and the economic advantages of such operations and therefore the importance to spread such an approach, it also highlights that it could be made technically easier and its performance could be even more 8.6 Effectiveness Analysis: A Path Towards Better Design Procedures 131 positive, although at present it proves a ‘field-tested’—yet not certified—efficiency, which shall be thoroughly assessed before being changed.

8.6 Effectiveness Analysis: A Path Towards Better Design Procedures

It is now clearer that flood proofing techniques to be deployed in the operational period by a civil protection service require less technical improvisation and a deeper analysis of site conditions by emergency planners; especially when compared to traditional practices of defensive measures, which are essentially based on the (anxious, because often not planned) use of sandbags, wooden boards and panels, in better cases—and not much more, e.g. metal plates—and last-minute evacuation. These protective measures being implemented during warning phases are still quite often untimely in protecting individuals and goods, and often do not meet the goal. This does not mean that such solutions should be excluded from operational options. In fact, being intuitive and quite widespread, they are an important first step towards more advanced competences—as shown by Pisa’s notable example, which is an excellent one from many points of view. Furthermore, in our case they have also allowed for the present discussion and served as a valid benchmark in a comparison to other recent temporary flood proofing techniques. It could be ascertained that these techniques generally offer improved tightness and lower costs, particularly over the medium term, although each temporary flood proofing technique or solution should be mainly assessed through adequate hazard analyses of individual event scenarios (Fig. 8.16).

Fig. 8.16 Milan (Viale Stelvio): a “non-professional/handcrafted” yet apparently efﬁcient water protection of a ventilation systems (picture of D.F. Bignami) 132 8 Temporary Flood Prooﬁng Techniques Planning

It must be pointed out once more that defensive solutions using such temporary flood proofing techniques do not usually involve changing soil usage in flood prone areas. Indeed, these solutions are indicated for the defense of existing heritages rather than new buildings. Essentially, they are more suitable for being used in Management plans of flood risks and less suitable for deciding on possible soil use. As a premise for using temporary flood proofing techniques in the emergency planning, a basic framework has been consequently provided of both time development of risk reduction measures during floodings and the overall multifaceted creation of water defense lines. Hence, it is now possible to focus on those criteria which allow choosing for effective results on the ground—following different aspects of effectiveness and efficiency. It is necessary to consider all these factors appropriately toattainanoptimalsolution—or the most suitable combination—towards a rational use in the specific context that is in need of protection. Such factors are not always of immediate intuition for decision makers, yet a better knowledge of them could surely foster their dissemination. The three following tables show their categorisation according to organisational elements of the SENSO model—Socio/economic context, Environment and event Scenarios, field Operations. Sometimes, these elements hinge on each other—or are intertwined—sometimes they become nearly independent variables; this is obvious, considering the magnitude of the options offered by the market. The first group of factors taken into account by the SENSO model are those regarding the reference “Socio-economic context” of the land chosen to be sheltered. This calls for economic, technical and human resources that can be deployed and made available for a specific defensive strategy option (Table 8.1). As provided for in the SENSO model, the second group of factors regards the reference “Environment and event Scenarios”. These factors allow selecting defense lines depending on the physical and natural context of the lands being sheltered, as well as on the expected flood event scenarios (Table 8.2). The third group of factors within the SENSO model helps to choose among temporary flood proofing techniques according to various aspects of the needed “field Operations” to put them in place, both in terms of operational manoeuvres and logistical implications (Table 8.3). 8.6 Effectiveness Analysis: A Path Towards Better Design Procedures 133

Table 8.1 The three categories of factors influencing the choice among temporary flood proofing techniques with regard to the SENSO model attribute of Socio-economic context Decision factors for using temporary flood proofing techniques—SENSO model Socio-economic context factors table S1—Available budget with regard to the area being protected. This could appear as the most obvious of all of the presented factors, however it must not be taken for granted. Indeed, not only do temporary floodproofing techniques involve a procurement cost, but also operational and maintenance costs (sometimes including costs of definitive dismantling and disposal of waste). These costs may also vary considerably based on to the available options. The use of temporary floodproofing techniques should consider the readily available budget for the intended purpose of implementation, taking into account the device’s life expectancy, in the framework a cost-benefit analysis; logically, this kind of assessment firstly depends on a calibrated choice of the importance of the targets being shielded, starting from main specific cases as priceless, i.e. human lives, and assets of historical and artistic value, which presumably will entail the use of the most effective techniques regardless of the economic implications. In general, decision makers have to consider costs reduction both in case of flood event (disaster relief, emergency costs, reduction in damages to public infrastructures and lifelines, etc.) and in insurance costs reduction, taking into account the probability functions in the considered period of time. Their integration in planning and emergency procedures will occur only once their availability and feasibility are effectively ensured, not exclusively upon planning of future purchases. Opting for a defensive strategy based on temporary flood proofing, and then implementing it partially due to economic reasons, means potentially incurring in a double mistake. When a defence line is only partially operational, its defence capability often does not drop proportionally, but totally, owing to water ‘mobility’. What is more, this would be a waste of time and money, since partial defenses would prove to be glaringly inefficient and stakeholders would be mislead about risk reduction within the land being sheltered. If purchased, operational/installation and storage/maintenance costs, as well as their safe useful life expectancy, are quite relevant concerning decision-making. Decision makers assessing expenses must not forget to take into consideration some aspects of further potential saving, medium-range, or multifunctional cost-effectiveness, such as reusability factors—with the same or any other event scenario—alternative use and the option of property-sharing. On this matter, see the different factors related to the Operational aspects (from O1 to O7). The available land positioning options of defense lines often impose technical choices that differ from the barriers being applied. Each different line will thus offer a different potential reduction of damage. The combination of such degrees of freedom shall be considered while evaluating the different economic aspects of the different options, with the result of sometimes increasing which their overall number. As far as this factor is concerned, it can be generally asserted that removable and pre-arranged/pre- located—or mobile—techniques could be less expensive than demountable techniques, although they depend on physical and morphological contexts as well as on event scenarios. Generally, the former are classified, according to the total cost, as “high”, “medium” and “low” on the basis of the following evaluation elements: 1. Procurement 2. Assembly/Disassembly, transport and clearance operations 3. Maintenance/storage (when not in use) 4. Reusability (in more than in one flood event) 5. Alternative use S2—Timely availability of trained workforce and/or possible self-employment for private individuals. The use of the most advanced temporary flood proofing techniques requires adequately qualified or trained work forces, however in many cases their numbers are only moderately high. (continued) 134 8 Temporary Flood Proofing Techniques Planning

Table 8.1 (continued) Decision factors for using temporary flood proofing techniques—SENSO model Socio-economic context factors table Most of these techniques are performed by private or public special services—firefighters or civil protection services—as well as volunteers, in cases of alert or alarm. Still, some techniques may provide for the self-employment of private individuals on their own—families, companies and so on. Such workforce or action capabilities should be promptly available in time of need. Such availability cannot be assumed, due to a number of socioeconomic parameters—community size, territorial distribution of population, second home owners, income levels, elderly population, etc. In fact, the choice of employing such techniques implies promptly ensuring their inherent action capability. By disregarding this factor, thus being incapable of using these techniques, the efforts made to acquire them might be fruitless; if a shop needs to manually position flood gates for protection, it has two options: either the advance warnings are issued sufficiently in advance for the shopkeeper to install them—public holidays may be particularly critical—or a public or private service should be appointed to install them for the shopkeeper. In this respect, pre-arranged/pre-located and above all demountable techniques generally—but not always—require less workforce for installation, deployment or on-site surveillance purposes during the events. The training complexity level to reach full action capability with flood proofing techniques could be listed as follows: 1. Specific training courses are required; 2. Technical (generic) skills at a professional level are required; 3. Self-employment is possible for private individuals (only for short line of defense); 4. Automatic solutions do not involve workforce—except for regular scheduled maintenance and surveillance. In this case also, the evaluation elements, in certain cases, could be classified according to a “high”, “medium” and “low” (need of workforce). S3—Availability of auxiliary means of transport and equipment. Many flood proofing techniques need the aid of vehicles to transfer waterway damming or diversion apparatus, as well as auxiliary or operational equipment for deployment at the intended sites—tools, air compressors, water pumps, power generators, cables, stay bars and so on. All this equipment should be effectively available at the very moment of need, both in terms of figures and in regard to suitability for transport and use—loading capacity and overall size, passableness of non-asphalted roads with heavy rain, fog, leaves, branches or other debris, sufficient power or voltage, etc. Without all this, as in the previous section, the whole real-time operational strategy and purchased goods would have been unproductive. The fact of being a necessity obviously implies taking them into account in the costs schedule in C1 factor. The availability of these tools can often be obtained through strong synergies with other technical and administrative bodies of public authorities. It is a fact that some techniques, in spite of an easier installation or better performance in damming water, may be bulkier or more complex than others, and conversely. Again, while making their choice, decision makers shall be asked to solve such trade-offs according to their own objectives. It should be clearly pointed out that this factor does concern demountable techniques only peripherally, apart from transport operations to reach the intended defense line as determined by the personnel designated for their activation and surveillance. Hence, temporary flood proofing techniques are divided in categories according to following properties: 1. Need for heavy auxiliary equipment and/or specific means of transport; 2. Need for light auxiliary equipment; 3. Need for specific means of transport (more than those related to the surveillance personnel); 4. No need for auxiliary equipment or specific means of transport. 8.6 Effectiveness Analysis: A Path Towards Better Design Procedures 135

Table 8.2 The four categories of factors influencing the choice among temporary flood proofing techniques in regard to the SENSO model attribute of Environment and event Scenarios Decision factors for using temporary flood proofing techniques—SENSO Model Environment and event scenarios factors table E1—Performances in relation to water level h, flow velocity v and solid transport values—i.e. event scenarios. The performances of a defense line based on temporary flood proofing techniques should be mainly assessed through a number of flooding characteristics, such as: water level h, flow velocity v and solid transport values—or floating materials—which they are able to withstand with a certain safety margin. Each temporary flood proofing technique indeed ensures different performance aspects, to be taken into account in comparison with those of different event scenarios which may occur. These types of use hinge on a number of elements, some of which are inherent to aspects of geometry, mass, inertia—which is able to oppose water action—resistance of used materials and deployment of specific apparatus. Thus, the event scenario to be addressed is vital to obtain the right solution. As regards to temporary flood proofing, the abovementioned parameters could be classified according to the following scheme, which is more detailed than the one presented in the previous Chap. 7, as it goes into details deeper than FEMA National Nonstructural Committee (FEMA 2012), since it moves from strategies to techniques. Water level: – Very low < 30 cm (1 ft.) – Low (30–60 cm) (2 ft.) – Moderate (60–90 cm) (3 ft.) – Elevated (90–120 cm) (4 ft.) – Very elevated (120–150 cm) (5 ft.) – High (>150 cm) Flow velocity: – Low (<0.9 m/s) – Moderate (0.9–1.5 m/s) – Rapid (>1.5 m/s) Solid transport and floating materials: – Low—sand or suspended soils, branches and other light floating materials – Medium—garbage containers, benches, tree trunks, furniture – Heavy—cars, motorbikes and electrical appliances – Boulders (rocks with size greater than 0.25 m in diameter) – Ice and Debris flows E2—Extension and type of span to be protected. The action of temporary flood proofing techniques consists in damming and deflecting water flow in order to shield areas at times very large, ranging from local (building) scale to territorial scale— which involves more than one municipality. As we already pointed out, their use normally involves linking points which at least equal the operational height of the chosen solutions—for example, through closed ring configurations—to avoid compromising technical performance. According to their positioning and the width of the defense line, some techniques may be more or less favourable in terms of laying time, resistance to water flow, needed personnel for on-site surveillance, cost-effectiveness—line length vs. goods or land being protected—and so on. As far as this factor is concerned, it can generally be pointed out that demountable techniques are usually more usable on shorter lines. For these reasons, their suitability for each possible type of defence line shall be assessed, as follows: – Advanced line – Intermediate line (block or deflection) (continued) 136 8 Temporary Flood Proofing Techniques Planning

Table 8.2 (continued) Decision factors for using temporary flood proofing techniques—SENSO Model Environment and event scenarios factors table – Inner line – Inner line forming a closed ring And/or their suitability to different lengths, namely: – Long – Medium – Short Given that each of the four options from the former group can match with one property from the latter. E3—Need for preliminary studies and site preparation depending on detailed ground morphology. The choice of a temporary flood proofing technique may be affected by different uneven soil surfaces, obstacles—such as trees, poles, fences, pavements, traffic dividers and so on—soil permeability, site orography—gradients and detailed heights (that is slope)—etc. Also, these elements may call for preliminary morphological preparation or adaptation/treatment of the specific ground designated for laying and using the intended solutions. Ideally, defense lines should be placed on reasonably levelled and empty soils—or at least compatible with the overall surface areas of selected or usable barriers—so that the barriers could adhere as tightly as possible to soil. This aims at ensuring maximum impermeability for the line, which seldom reaches levels of total impermeability—many times, in contexts of heavy rain, such goals constitute no critical or significant issue (since small water leaks are normally harmless), which nonetheless can be tackled by means of water pumps, if necessary. Erodible soils should be generally avoided, namely sandy, melted or marshy soils. Permanent meadows and vehicular surfaces such as asphalt, tarmac, concrete or pavé are preferred instead. In the territorial planning phase, if necessary and no valid alternative is available, territorial equipment activities can entail minor public works focused on soil arrangement for placing the chosen solutions on defence lines. Temporary flood proofing techniques are consequently classified in categories according to the following properties: – Suitable for levelled and empty hard surfaces, to be selected or prepared (techniques apt to work only on hard, flat and reasonably smooth surfaces—asphalt, concrete, etc.); – Suitable for almost all types of reasonably levelled and empty surfaces, to be selected or prepared (techniques apt to also work on relatively irregular surfaces (grassy ground, uneven or stony ground, etc.). – Suitable for almost all types of reasonably levelled and empty surfaces and apt to be a component of a ‘reserve unit’ of intervention in case of unexpected events occur to the defence system. E4—Building types, ranging from foundations to construction materials, as well as urbanization context of the constructions being protected. The range of available alternatives may be influenced by foundation types, construction systems and materials, as well as the local urbanisation context—this is particularly valid for European contexts, where blocks with adjacent buildings are more often found. As an example, soils can give different responses to floods; some may be saturated and liquefy, therefore in the zone where the stability of buildings is at stake this must be avoided by disregarding impermeabilisation options and aiming for alternatives that might keep water away. Moreover, walls can oppose or help withstand water action differently, according to their general state of maintenance or materials. Project designers shall therefore assess whether it is appropriate to utilise them in resisting water flow and pressure. Given the huge variety of building types and construction techniques, for this factor it is not possible to provide a comprehensive classification as to the choice of temporary flood proofing techniques. However, it is rational to at least consider: (continued) 8.6 Effectiveness Analysis: A Path Towards Better Design Procedures 137

Table 8.2 (continued) Decision factors for using temporary ﬂood prooﬁng techniques—SENSO Model Environment and event scenarios factors table – The more suitable to be used set/propped against concrete or masonry buildings; – The more suitable to be used set/propped against every kind of buildings (wood or light buildings included; crawlspace foundations excluded); – The more suitable to be used set/propped against cultural heritage buildings – The more suitable to be used away from buildings.

Table 8.3 The seven categories of factors influencing the choice among temporary flood proofing techniques in regard to the SENSO model attribute of field operations Decision factors for using flood proofing techniques—SENSO model Field operations factors table O1—Speed of installation and deployment. This factor is crucial as it regards event frequency and the time made available by the warning system, as well as to the size and weight conditions of the defense line being arranged. Indeed, the time needed for positioning and deploying the equipment is essential not to nullify the planned operations. As we already mentioned, some techniques require preliminary preparatory activities that cannot be undertaken during flood events, particularly, but not only, in respect of demountable techniques. Time consideration for these techniques corresponds to their deployment, given that they are already arranged and positioned. As for temporary techniques, the time span of reference will be that of full installation, even though soil arrangement and transport time are not included. Apart from the considerations made so far on the factors regarding the socioeconomic context and those pertaining to the environment and the event scenarios, there is no doubt that shorter times of installation or deployment per each linear metre of defense line are an advantage. Furthermore, temporary flood proofing techniques may require very different times of installation and deployment. Similarly, short times and more easiness of dismantling (often of the same order of magnitude of what asked for the installation) could simplify precautional decisions of use, giving more chance of a correct flood defense policy. To this aim, we intend to further detail the content of Fig. 7.20 in regard to “Flash Flooding” by specifying the available time for the installation (performed by two workers with the available equipment) of a standard barrier (or, in case, at most of 20 Â 1 m) into the following categories: – None/instantaneous (also feasible in the presence of a water sheet, even if not desirable) – <1h – 1–3h – 3–6h – 6–12 h – 12–20 h – >20 h O2—Potential reuse and multipurpose use, in different flood events or for ‘alternative’ purposes. When choosing whether to utilise a solution to oppose a certain flood event, knowing about reusability chances and criteria for goods that are about to be acquired could be a matter of the utmost importance for decision makers. The first significant aspect to be considered is the degree of ‘mobility’ of barriers, that is their usability on different defense lines—which is extreme for some techniques, sometimes ‘unlim- ited’—to meet the requirements of different event scenarios. As far as this factor is concerned, it goes without saying that demountable techniques do not have such features, unlike removable (continued) 138 8 Temporary Flood Proofing Techniques Planning

Table 8.3 (continued) Decision factors for using flood proofing techniques—SENSO model Field operations factors table flood proofing techniques. The mobility of the latter, in regard to overall dimensions, weight and potential anchoring, is not necessarily agile in all possible cases. In addition, some temporary flood proofing techniques may be useful for other types of civil protection and public security operations, such as building water basins for fighting against forest fires, retaining water and air pollutants, creating blockades to restrict car and pedestrian access to specific areas, etc. Thus, they can generate operational synergies and savings. Hence, here is a classification to evaluate this factor, namely: – Non-mobile apparatus, non-usable for different purposes – Non-mobile apparatus, possibly usable for blocking pedestrians or vehicles – Light mobile apparatus, non-usable for different purposes – Heavy mobile apparatus, non-usable for different purposes – Light mobile apparatus, reusable and usable for different purposes – Heavy mobile apparatus, reusable and usable for different purposes – Mobile apparatus requiring anchoring O3—Preliminary territorial equipment and possible minor requirements for territorial infrastructures. Some temporary flood proofing techniques provide for preliminary action prior to their use and for possible minor requirements for territorial or building infrastructures in order to be placed and deployed as planned in the identified defense lines (this need is not to be mismatched with site preparation). The choice of specific techniques implies necessary action to carry out anchoring operations or even light territorial infrastructural measures, such as the locking devices secured to small foundations and rails, or even the implementation of control systems, sometimes automatic— especially for demountable techniques—as in the case of a number of collapsible (liftable) solutions that are lodged directly by the defense line. Such needed action affects costs and mobility for reuse purposes on different defense lines that are designed to respond to different event scenarios. Hence, here is a classification to evaluate this factor, namely: – Apparatus requiring ‘heavy’ territorial equipment – Apparatus requiring ‘light’ territorial equipment or building arrangements – Apparatus which does not need any territorial equipment O4—Availability of materials and additional apparatus. The reconstruction of event scenarios is always subject to uncertainty. The equipment needed to put together the defense lines may be partially estimated, although the procurement phase can be undertaken with an appropriate safety margin. Unexpected sub-events may always occur—collapsed bridges obstructing sections of watercourses, landslides, riverbeds clogged up by bulky waste, and so on. When necessary, at the moment of need the chosen apparatus is nonetheless available only to a limited extent. While choosing the right defensive technique, timely availability of additional provisions therefore should be assessed and, similarly, the related availability of trained personnel and suitable equipment for transport and use. Concerning this, it can be clearly inferred that a protection strategy utilising only defense lines based on demountable techniques are firmly anchored and quite resistant, whereas some more flexible techniques may hardly be available in real time or cannot be installed due to a lack of infrastructural measures at a territorial level. In pre-arranged/pre-located cases, more arrangements, rails and connections can be designed and positioned in many land points—within different municipalities, in case of a cooperation—compared to barriers—this decision should be taken only with independent and mutually exclusive (not occurring in any case at the same time) event scenarios. Hence, here is a classification to evaluate this factor, namely: (continued) 8.6 Effectiveness Analysis: A Path Towards Better Design Procedures 139

Table 8.3 (continued) Decision factors for using flood proofing techniques—SENSO model Field operations factors table – Additional apparatus not available in real time – Additional apparatus easily available in real time from specialist suppliers, yet requiring territorial equipment – Additional apparatus easily available in real time from specialist suppliers – Additional apparatus easily available in real time from normal suppliers O5—Removability and induced residual environmental impact at the end of the flood event. At the end of an event, any leftover abandoned on land induces a residual environmental impact. Solutions might have different impacts in this sense, so their removability can sometimes be decisive from an economic and social point of view. In this regard, demountable techniques certainly have a permanent impact on soil, however known and taken into account since the beginning (being self-stored and aesthetically designed to be unobtrusive when not in use against flood). Some solutions leave significant residuals—especially solutions whose lifetime is equivalent to a single use—while other solutions do not leave any. Hence, here is a classification to evaluate this factor, namely: – Light apparatus leaving no residuals (fully removable) – Heavy apparatus leaving no residuals (fully removable) – Apparatus leaving considerable residuals – Apparatus inducing reduced permanent changes to premises – Apparatus inducing significant permanent changes to premises O6—Quality and quantity of storage areas, when not in use. Temporary flood proofing techniques call for the use of apparatus which needs to be stored or lodged in suitable areas when not in use, according to quality and quantity requirements. Moreover, it must be easy to access, open, monitor or protect, inspect and handle. Storage areas, if possible, must be chosen among alternatives near the associated defence lines to shorten time-to-action. As concerns demountable techniques, such areas correspond to the same site where barriers are positioned on land (being self-stored). As for pre-arranged/pre-located and removable techniques, they depend on properties such as collapsibility or compaction—allowing for different storage of linear metres of barriers per cube metres of occupied storage volume—lifetime perishability of materials or time-related deterioration of the technical features of some components—gaskets, waterproofing seals and so on—in proportion to weather and environmental conditions, either indoors or outdoors. Hence, here is a classification to evaluate this factor, namely: – Visible apparatus stored in (along) the defence line – Fold-up apparatus stored in (along) the defence line – Collapsible mobile apparatus requiring no safe storage against atmospheric agents – Non-collapsible mobile apparatus requiring no safe storage against atmospheric agents – Removable apparatus requiring safe storage against atmospheric agents – Removable apparatus requiring no safe storage against atmospheric agents – Collapsible apparatus requiring safe storage against atmospheric agents – Non-collapsible apparatus requiring safe storage against atmospheric agents O7—Maintenance requirements, operating times and potential repairs in case of damage, even when operational. Temporary flood proofing apparatus often requires regular maintenance operations in order to keep its technical performances effective as long as possible. Sometimes it may be damaged during events and therefore require, if possible, to be repaired while operational in the defence line. Even good sense says that equipment that is idle for most of its lifetime may be ‘forgotten’ between events. This is less likely to occur if it can serve multiple uses; inspection, maintenance and regular replacement programs help particularly if they are part of ordinary operations, to avoid unsatis- factory performances. Logically, needs of frequent maintenance could be heavy to be organized, (continued) 140 8 Temporary Flood Proofing Techniques Planning

Table 8.3 (continued) Decision factors for using flood proofing techniques—SENSO model Field operations factors table less frequent needs could be often preferable. In case of partial failure or damage, some apparatus may allow for repair in spite of being operational on the defensive line, whereas some others may allow for partial on-site replacement of damaged components, under specific conditions. Here is a classification to evaluate this factor, namely: – Apparatus reparable/replaceable on-site, requiring frequent and regular maintenance – Apparatus reparable/replaceable on-site, requiring sporadic and regular maintenance – Apparatus reparable/replaceable on-site, requiring no maintenance – Apparatus non-reparable/non-replaceable on-site, requiring frequent and regular maintenance – Apparatus non-reparable/non-replaceable on-site, requiring sporadic and regular maintenance – Apparatus non-reparable/non-replaceable on-site, requiring no maintenance

References

Alexander DE (2000) Confronting catastrophe. Oxford University Press, New York Arrighi C, Castelli F (2014) A ‘what if’ scenario: Pisa, February 2014, without existing flood protection. In: Resilienza delle città d’arte alle catastrofi idrogeologiche: successi e insuccessi dell’esperienza italiana. Accademia Nazionale dei Lincei, Roma, 4–5 novembre Arrighi C, Brugioni M, Castelli F, Franceschini S, Mazzanti B (2013) Urban micro-scale flood risk estimation with parsimonious hydraulic modelling and census data. Nat Hazards Earth Syst Sci 13:1375–1391 Bignami DF (2010) Protezione civile e riduzione del rischio disastri. Maggioli, Sant’Arcangelo di Romagna Dircke (2015) NAP Expo 2015: realizing the NAP process. Bonn, 14–15 Apr 2015. http://www. adaptation-undp.org/nap-expo-2015 DPC – Dipartimento della Protezione Civile presso la Presidenza del Consiglio dei ministri, Repubblica Italiana (2007) Manuale Operativo per la predisposizione di un piano comunale o intercomunale di protezione civile, ottobre DPC – Dipartimento della Protezione Civile presso la Presidenza del Consiglio dei ministri, Repubblica Italiana, a cura di Elvezio Galanti (1997) Metodo Augustus. In: DPC INFORMA – Periodico informativo del Dipartimento della Protezione Civile, Numero 4 Maggio-Giugno FEMA (2012) Principles and practices for retrofitting flood-prone residential structures, 3rd edn. FEMA P-259/January 2012 Fournier d’Albe EM (1979) Objectives of volcanic monitoring and prediction. J Geol Soc Lond 136:321–326 Granger K (2003) Quantifying storm tide risk in cairns. Nat Hazards 30:165–185 Grünthal G, Thieken AH, Schwarz J, Radtke KS, Smolka A, Merz B (2006) Comparative risk assessments for the city of cologne—storms, floods, earthquakes. Nat Hazards 38:21–44 ISO 31000:2018 (en) Risk management – guidelines, 2nd edn Keegan J (2003) Intelligence in war: knowledge of the enemy from Napoleon to Al-Qaeda. Alfred A. Knopf, New York Kron W (2005) Flood risk ¼ hazard Á values Á vulnerability. Int Water Resour Assoc—Water Int 30 (1):58–68 Pine J (2015) Hazards analysis. CRC Press, Boca Raton. ISBN: 9781482228922 Provincia di Pisa (2014) Panconi per il sovralzo delle spallette dei lungarni di Pisa, Dipartimento del Territorio, Servizio Difesa del Suolo – U.O. Opere idrauliche e marittime (nota per il Politecnico di Milano) Chapter 9 Temporary Flood Proofing Devices Analysis

9.1 Recapitulating

As we have already pointed out, temporary flood proofing techniques include a broad variety of solutions. To capitalise on their potential, it is necessary to be familiar with some use-related criteria, as suggested by the SENSO Model, shown and deeply described in Chap. 8. Indeed, as already said, these real-time defence measures need to be undertaken following the establishment of specific warning phases or instructions as provided by the local monitoring and territorial civil protection services (Bignami 2010). Their widespread use as a customary and significant waterproofing strategy cannot be left up to chance. Rather, it should be examined, promptly arranged and illustrated in a dedicated section of the civil protection contingency plan, i.e. the Temporary flood proofing response plan. Clearly focusing on defence line maps, its implementation should involve professionals or specifically selected and trained operators as part of the Temporary flood proofing special service (at least to supervise the programmed defence action of citizens in their property). Such measures are aimed at risk reduction, mainly through a resistant approach, by acting on the local hazard of different areas as well as the vulnerability of buildings. In so doing, at an urban scale, the cooperation of many local resistant actions triggers a resilience strengthening of the flood prone communities (Chou and Wu 2014). Moreover, they can be divided into three main sub-categories, i.e. removable, pre-arranged/pre-located and demountable (liftable) techniques. The first techniques are fully mobile, promptly transported and/or assembled on the defence line (including “last minute” planning) only when necessary and completely removed after the flood event; the second techniques, partially pre-installed, partially removable, are transported and/or assembled on the planned and laid defence line only when necessary; the third techniques are secured to the ground or to the buildings, play a permanent role within the defence line (where they are stored) and are simply triggered or deployed when necessary (fully pre-installed).

As anticipated, our discussion about temporary flood proofing will concern techniques that are primarily based on strategies such as Floodwalls C and Dry flood proofing D, and only secondarily on Wet flood proofing E and Ground lowering/levelling of free land G—which can also be used in an integrated form, and if needed in several adjoining defence lines. In particular, they have been grouped as follows: C.R.1 (Floodwalls Removable group 1)—Stacking of individual base units filled with solid materials acting on gravity, including traditional emergency dikes made of sandbags—which are a sort of benchmark of our classification—temporary dikes containing reinforced earth/loose soil, as well as bags filled with innovative absorbent materials; C.R.2 (Floodwalls Removable group 2)—Supportive/juxtaposed use of fluid containers, including modular tubes or containers to be filled with air or water (temporary barriers); C.R.3 (Floodwalls Removable group 3)—Self-deploying or self-supporting mobile barriers, including self-inflating barriers or barriers with a reticular structure; C.R.4 (Floodwalls Removable group 4)—Emergency dikes and/or berms of loose solid material, including temporary earth levees/dikes and barriers of stone/ concrete blocks; C.P.1 (Floodwalls Pre-arranged/Pre-located group 1)—Temporary barriers/ shields with especially crafted anchoring (temporary waterwalls), including temporary anchored vertical barriers (shields, gates and panels); C.D.1 (Floodwalls Demountable group 1)—Fixed retractable barriers including some automatic vertical gates (barriers); D.R.1 (Dry flood proofing Removable group 1)—Full dry flood proofing of buildings, including the wrapping and the packing of vertical walls with waterproof sheets (panels); D.P.1 (Dry flood proofing Pre-arranged/Pre-located group 1)—Selective dry flood proofing with customized watertight protections, including temporary shields or panels, watertight seals to prevent potential water seepage into the buildings (one-piece or sectional, thus more innovative than wooden boards); D.D.1 (Dry flood proofing Demountable group 1)—Selective dry flood proofing with demountable watertight protections, precisely and permanently customized, including watertight doors and windows and some automatic vertical shields; D.R.2 (Dry flood proofing Removable group 2)—Complementary dry flood proofing of buildings by means of removable universal apparatus, composed by industrially produced devices thought to seal the most of common openings; C/D.1—Mixed solutions and special cases, either cooperating—supporting one another—or collaborating—working side by side (including techniques to protect special outdoor goods). E.R.1—(Wet flood proofing Removable group 1)—Hydro-repellent sacs or similar protections systems for indoor movable goods, as big sealable plastic bags; 9.2 Description of Temporary Flood Proofing Proposed Classes 143

G.R.1—(Ground lowering/levelling of free land Removable group 1)—Water diversion temporary activated pipes or bridges, composed by devices which do not stop but deviate water. The purpose of such a variety of strategic classes of measures is to underline the differences among the numerous types of temporary flood proofing techniques that are mostly available to decision makers and civil protection services, as well as to individual citizens. Obviously, this is not intended to be an exhaustive list of all techniques which can be found on the market.1 On the other hand, it aims at showing the complexity of an evaluation process that should gradually result in a more informed choice, according to the various warning and response services by the civil protection, physical and social characteristics of the lands in need of defence and future event scenarios. The objective, thanks to the SENSO model application to each of these classes and their main declinations/variations, is to provide some independent methodological support which might be easily updated and used to make a careful distinction among many different measures, even considering those factors that are not included in this work—inevitably, thanks to research and development processes, techniques will evolve after the publication of this work—and analysing any specific issues or service/product innovations that may be released on the market in the future. Below is the reasoned exposure of the different classes (or groups).

9.2 Description of Temporary Flood Prooﬁng Proposed Classes 9.2.1 C.R.1 (Floodwalls Removable Group 1): Stacking of Individual Base Units Filled with Solid Materials Acting by Gravity

This group includes traditional emergency dikes made of sandbags—which are, as already stated, the benchmark of our classiﬁcation—temporary dikes built of containers of reinforced or loose soil, as well as bags ﬁlled with innovative absorbent materials. Clear reference is made to measures where elements either act individually or, more often, are juxtaposed, stacked up or overlaid in several rows. These act as a sort of shielding bricks, sometimes even substantial in size, and can comprise a huge number of base units. Essentially, such basic elements are able to counter water action due to their mass or the sliding friction placed on them by gravity, which

1Hence, neither has any substantial quality assessments been given for the different products and/or solutions available on the market by specific companies, nor any advice has been implied by the authors on specific techniques with regard to others not included in this work—despite the notable research effort. 144 9 Temporary Flood Proofing Devices Analysis allows them to oppose the incoming water pressure since either the level of tightness is exceeded or water has already overflowed—(according as the defence line is advanced or not.) The measures offered by this group generally call for the installation of rather heavy defence lines and large footprint surface areas.

9.2.1.1 C.R.1.1: Sandbags

Bags made of hessian (otherwise hemp, canvas, propylene or similar materials) and filled with sand (or soil) are the most well-known temporary flood proofing solution because of their basic concept, their easy availability and their relatively simple use; a familiarity that is also a reflection of their popular use for military purposes. Bags are definitely inexpensive and are easy to get and store. They do not take up too much space and are lightweight for easy transportation. Sand or soil are often found on the spot where the defence line is installed or are obtained from the usual suppliers through common established practices—though sometimes onerous and beyond the desired time frame. Their use only requires great availability of untrained workforces and tools in order to fill the bags one at a time. For such reasons, these bags have traditionally been an easier option to manage critical situations, where military forces or untrained volunteers have often been summoned or involved to intervene and join the effort of public administration and civil protection services whose resources had turned out to be partially inadequate. In spite of these pros, the use of such labour intensive techniques happens to be complicated on a large scale and often ill-timed manner Also, it is recommended only for people in great physical shape. Things can get worse when sand needs to be carried to the defence lines by means of suitable means of transport, such as lorries or vans. For instance, Pisa’s civil protection service stores filled sandbags in specific warehouses for such reasons, a solution which surely lowers the response time but demands wider storage areas—see previous chapter. In addition, stacking bags up may seem rather easy, yet if performed in an unprofessional manner—without prior appropriate training—it could result in dikes whose height and/or degree of water tightness and stability differ from what is expected, thus jeopardising the whole defence operation. Dikes made of sandbags cannot stand long operational periods, as the action of water and atmospheric agents may cause them to deteriorate and disassemble to a certain extent, thus declining defence performances. In the event of polluted waters (e.g. by hydrocarbons or sewage, which is fairly common during a flood), the already onerous operation to dismantle a dike becomes even more complicated owing to the necessary, proper disposal procedures of any waste which might be classified as special or hazardous, in accordance with the applicable legislation of the country in which they are being handled. The great number of handling operations generally focus on stacking up the bags on open ground after removing any dirt and debris, as much as to set up even long dikes of a typically triangular section (usually when their height goes beyond three layers of bags), normally, but not always, isosceles. Such an arrangement is 9.2 Description of Temporary Flood Proofing Proposed Classes 145

Fig. 9.1 Sandbag pyramid: transverse section (by way of an example—drawing not in scale)

Fig. 9.2 Sandbag pyramid: front view (by way of an example—drawing not in scale) necessary to ensure stability to the pile and is technically referred to as pyramid placement method. Its base length should be at least between 2 and 2.5 times—up to 3—the established height of the dike being erected. Some dikes can consist of thousands or even tens of thousands of units, see Figs. 9.1, 9.2 and 9.3. Bags should be arranged one layer on top of another, making sure that each upper bag overlaps the one below by half (like in the case of a brick wall).2 In general, they are

2For other techniques too it is recommended to stack bags (if rectangular), if need be, by keeping the dike in the shape of a pyramid, so that each layer is laid at right angles upon the lower one (in a ‘warp and weft’ pattern). 146 9 Temporary Flood Prooﬁng Devices Analysis

Fig. 9.3 Sandbag pyramid: plan view (by way of an example—drawing not in scale) rectangular in shape and need to be half-filled (but they are commercially available also in trapezoidal shape, to be arranged in inverse position one next to the other in the same row—(see Fig. 9.4). In some cases, a bag can simply be closed by folding its empty flap under the bag itself while it is being placed into the dike. When the critical water velocity or flood duration are reasonably high, these dikes can be bolstered with PVC sheets so as to increase water tightness due to their waterproofing action, which does not ensure a complete seal. For example, when laying a dike on open ground, sheets should be fixed on the water side by using gravity, acting on the bags already on top of the dike, and positioning a single additional row in front of the dike on the water side (see Fig. 9.1). If a dike is laid to protect doors or gates, the plastic sheets are to be placed below the pile, still making use of the gravity on the bags, then they should be unfolded to properly adhere to the door being propped by the bags. To reduce potential seepage at the bottom level, some additional bags could be just placed onto the first soil layer under the pyramid (bonding trench). In doing so, water absorption could be minimised, therefore improving the water tightness of the defence line as well as the stability of the dike. However, sandbags are generally well-suited to the different ground types on which they are laid. This is why, if their fastness is ensured, sometimes they can even have a temporary antierosive effect. Not only can sandbags be filled manually by at least two people, but sand can also be mechanically conveyed with the aid of gravity-based systems that are able to clutch and support one or more bags (sandbag filling machines). Thanks to this kind 9.2 Description of Temporary Flood Proofing Proposed Classes 147

Fig. 9.4 A selection of representative examples of sandbags technique 148 9 Temporary Flood Proofing Devices Analysis of machines, the filling/time of sandbags can be shortened, and sometimes also the time of construction of a barrier, as in the case of using “special sandbags” called continuous tubing, reaching the length of tens of meters. Even if they are built accurately and professionally, such dikes tend to deteriorate rather quickly and have low stability against water flow, mainly on top of the pile forming the sandbag pyramid (especially in the event of an overflow or with floating materials of a certain size, such as tree trunks, furniture, garbage containers and so on). Indeed, the higher layers of such dikes are not heavy enough, unlike the lower ones, to overcome both the lack of internal cohesion among the constituent elements of the dike and that of anchoring and securing devices. The strength of the dike is therefore inversely proportional to the height of the sandbag layer that is taken into consideration. For this reason, such dikes must be erected by stacking an overabundance of elements heightwise, acting as a freeboard. Nonetheless, sandbags still remain one of the most flexible, yet less ‘specialised’ solutions of temporary flood proofing and adapt to any type of defense line (if there is enough space), whether they be advanced, intermediate or inner. This is another reason why they are a sort of functional benchmark for our argumentation. Quite often, they are chosen to refine, complete, integrate or strengthen the use of other temporary flood proofing techniques (e.g. as regards discontinuities and end connections—see Sect. 8.4.3). Hence, as provided for by a temporary flood proofing response plan, like other techniques, they can be an important component of a ‘reserve unit’ whose aim is to intervene in case any unexpected event occurs to the defence system. To improve durability and water tightness performances, which itself is not absolute, sandbags can be filled with a mix of sand and concrete. On one hand, this choice manages to boost some performances; on the other hand, some other performances are inevitably compromised in terms of durability and stability, such as disassembly conditions and reusability. Table 9.1 shows a detailed schematisation of their characteristics in comparison with the distinguishing factors that have been determined to choose among temporary flood proofing techniques. Figures 9.1, 9.2 and 9.3 indicatively show ways to use this kind of techniques.

9.2.1.2 C.R.1.2: Rapidly Deployable Earth-Filled Dikes

This option differs from the previous one in terms of size, shape and compactness of the individual units of the dike. These containers (or bags) are vertical, generally opened on top, bigger than sandbags and usually have a cubic or parallelepiped shape. Their fabrics (geotextile) have the ability to contain more or less fine materials and are reinforced by either supporting structures or metal and/or wooden mesh (gabions). After being placed on the defence line (or nearby), they are filled with 9.2 Description of Temporary Flood Proofing Proposed Classes 149

Fig. 9.5 Earth-filled dike/dam: transverse section (by way of an example—drawing not in scale) sand, river silt, earth, gravel (stone-bags), crushed stone, mixed materials or concrete just before they are put into operation. If considered as standing on the same base surface (footprint), they usually allow to obtain higher dikes and resist higher forces as opposed to sandbags, also regarding solid transportation (tree trunks, vehicles, garbage containers, mudslides and so on). Attention should be therefore paid to the sections of Figs. 9.1 and 9.5, i.e. d1 > d2, or similarly, where this measure can take up a relatively smaller area on equal dike heights. Furthermore, this option provides for temporary connection and anchoring solutions both to the ground and among the units forming the dike—thus permitting to organize honeycomb structures on multiple lines—instead of simply taking advantage of gravity in opposing water action. In case loose material, soil, gravel or stones are used, containers to be placed on the water side can be made of (or wrapped in) waterproof cases (cloth/textile). When necessary, the elements can be stacked up into several rows, not only lengthwise but also heightwise—overlapped, still using a pyramid-shaped structure—to withstand scenarios which may produce even outstand- ing water heights. Due to its characteristics, this solution is logically more feasible than sandbags on advanced or intermediate defence lines, as it necessarily entails the use of expensive and bulky earth-handling machinery to be fulfilled (mechanical-movers). Therefore, they imply nothing but a more specialised use compared to the previous technique, asking, in particular, for specific activities of procurement and training. The ISO metal container is the extreme case of this category (2.44 m wide, 2.59–2.90 m high, and 6.10 or 12.20 m long; unladen weight from 2.1 to 3.7–4.2 tons). Its sides are waterproof and its loading space can be filled with heavy materials (such as stones, gravel, sand, etc.) to increase its weight and ensure stability to the ground even with stronger pressures (as, for instance, in case of marine waves). Table 9.1 shows a detailed schematisation of the abovementioned characteristics in comparison to the distinguishing factors that have been determined to choose among temporary flood proofing techniques. Figures 9.5 and 9.6 approximately show ways to use this kind of techniques (Fig. 9.7). 150 9 Temporary Flood Proofing Devices Analysis

Fig. 9.6 Earth-ﬁlled dike/dam: front view (by way of an example—drawing not in scale)

Fig. 9.7 A selection of representative examples of rapidly deployable earth-ﬁlled dikes technique 9.2 Description of Temporary Flood Prooﬁng Proposed Classes 151

9.2.1.3 C.R.1.3: Bags Filled with Innovative Materials

The basic idea of this kind of technique is to improve some of the performance properties of stacked sandbags acting by gravity through the use of innovative materials (such as hydrophile). These, when dry, generally have a lower volume and weight than sand (less than one to two size and weight order of magnitude). When submerged in water and absorbing it, more than decupling weight (for instance from about 0.5 kg to more than 20 in about 3–5 min) and volume, they should get into operation and offer equal or even better tightness performances. Basically, from the temporary floodproofing techniques classification point of view, this “sandbag-sandless” technique is borderline, if compared to the next category, since it results from a mixed counteraction between solid and fluid materials. After use, usually for a time of no more than 3 months, the disposal of the internal material of this kind of sandbag is that of a household waste. The external material sometimes is plastic, sometimes is biodegradable. But frequently these units are internally and externally made of environmental-friendly materials and, if not in touch with pollutants during the flood, they can also be reused for gardening or forestry activities. In general, they do not allow for multiple uses in flood proofing strategies, because they cannot be dried and regain their initial properties. Although these sacs are technically usable in the same way as the sandy ones, they are particularly practical in civil or domestic uses as they tend to be quite clean and they not only stop the water, but they absorb it. From an operational point of view, they can also be positioned dry, when the arrival of the water is not sure. When used more for their absorbing rather than damming properties, these measures can sometimes be used to collect spilled liquids other than water, liquids that can occasionally be polluting. In other cases, ‘shape’ innovations have developed longer bags with a shorter diameter and/or occasionally with non-circular cross-sections, i.e. triangular, so as to foster their domestic use and counter even the smallest seepage. Indeed, they have enhanced the sandbag technique so that some performances have improved in respect to greater costs and a more thorough planning strategy in providing for material supplies to build the intended defence lines. For this reason, they are logically more usable with low water heights or short barriers, and are particularly suitable for inner defencelines,beingalsoeasilymanageable and storable. Table 9.1 shows a detailed schematisation of the abovementioned characteristics in comparison to the distinguishing factors that have been determined to choose among temporary flood proofing techniques. Figure 9.8 schematically shows ways to use this kind of techniques (Fig. 9.9). 152 9 Temporary Flood Proofing Devices Analysis

Fig. 9.8 Bags ﬁlled with innovative materials: front view (by way of an example—drawing not in scale)

Fig. 9.9 A selection of representative examples of bags ﬁlled with innovative materials technique 9.2 Description of Temporary Flood Prooﬁng Proposed Classes 153

Table 9.1 Sandbags, rapidly deployable earth-filled dikes and bags filled with innovative materials: SENSO model evaluation elements SENSO model factors Floodwalls removable C.R.1—Solid materials filled units acting by Solution group gravity Rapidly deployable Bags filled with earth-filled dikes innovative materials Techniques Sandbags (C.R.1.1) (C.R.1.2) (C.R.1.3) Socio-economic context—(S) (S1) Available budget with regard to the area being protected 1. Procurement Low Medium High 2. Assembly/disas- High High Medium sembly, transport and clearance operations 3. Maintenance/stor- Low (except for Low Medium age (when not in use) already filled bags) 4. Reusability Not always None None (in more than in one flood event) 5. Alternative use Rare (civil defense) Rare (civil defense) Response barrier for pollutant spills and leaks Occasionally, if wet after flood, are useful for gardening activities (S2) Timely availability of trained workforce and/or possible self-employment for private individuals 1. Specific training Low (only for techni- Medium (technical None courses are required cal directors or super- directors or supervi- visors in case of long sors, foremen) defense lines) 2. Technical (generic) High (for workforces, Medium (for work- Low (for workforces skills at a professional with respect to the forces and drivers of with respect to the level are required length of the defense mechanical earth- length of the defense line) movers) line) 3. Self-employment is Low (easy training None Yes possible for private and quick preparation) individuals (only short line of defense) 4. Automatic solu- None None None tions do not involve workforce—except for regular scheduled maintenance and surveillance (continued) 154 9 Temporary Flood Proofing Devices Analysis

Table 9.1 (continued) SENSO model factors Floodwalls removable C.R.1—Solid materials filled units acting by Solution group gravity Rapidly deployable Bags filled with earth-filled dikes innovative materials Techniques Sandbags (C.R.1.1) (C.R.1.2) (C.R.1.3) (S3) Availability of auxiliary means of transport and equipment 1. Need for auxiliary Need for specific Need for heavy auxil- None (for short lines) equipment or specific means of transport iary equipment and/or means of transport (more than those specific means of related to the surveil- transport (to move lance personnel)— sand or gravel and (to move sand and, if mechanical earth- necessary, for filling movers) machines and draining pumps) Environment and event scenarios—(E) (E1) Performances in relation to water level h, flow velocity v and solid transport values—i.e. event scenarios Water level High High Very low to moderate Flow velocity Rapida Rapid Lowa Solid transport and Lowa (sand or Heavy (cars, motor- Low (sand or floating materials suspended soil, bikes and electrical suspended soil, branches and other appliances) branches and other light floating light floating materials) materials) (E2) Extension and Suitable for all types Suitable for advanced Suitable for interme- type of span (or spans) of defence lines and and intermediate diate and inner lines being protected all different lengths (block or deflection) and for short lengths defence lines Suitable for all different lengths (but longer than sandbags at the same time) (E3) Need for prelim- Suitable for almost all Suitable for almost all Suitable for levelled inary studies and site types of reasonably types of reasonably and empty hard sur- preparation depending levelled and empty levelled and empty faces, to be selected on detailed ground sur-faces and apt to be sur-faces, to be or pre-pared (tech- morphology a component of a selected or prepared niques apt to work ‘reserve unit’ of inter- (techniques apt to also only on hard, flat and vention in case of work on relatively reasonably smooth unexpected events irregular surfaces surfaces—asphalt, occur to the defence (grassy ground, concrete, etc.) system uneven or stony ground, etc.) (continued) 9.2 Description of Temporary Flood Proofing Proposed Classes 155

Table 9.1 (continued) SENSO model factors Floodwalls removable C.R.1—Solid materials filled units acting by Solution group gravity Rapidly deployable Bags filled with earth-filled dikes innovative materials Techniques Sandbags (C.R.1.1) (C.R.1.2) (C.R.1.3) (E4) Building types, suitable to be used Suitable to be used Suitable to be used from foundations to set/propped against away from buildings set/propped against construction materials concrete or masonry every kind of build- and urbanization con- buildings, as well as ings (wood or light text of constructions away from buildings buildings included, crawlspace foundations excluded), as well as away from them and set/propped against cultural heritage buildings Field operations—(O) (O1) Speed of instal- Time needed for the Time needed for the Time needed for the lation and deployment installation installation installation (performed by two (performed by two (performed by two workers with the workers with the workers with the available equipment) available equipment) available equipment) of a barrier of of a barrier of of a barrier of 20 Â 1m:>20 h (less 20 Â 1m:1–3h 20 Â 1m:12–20 h if using sandbags filling machines) (O2) Potential reuse Heavy mobile appara- Heavy mobile appara- Light-mobile appara- and multipurpose use tus, non-usable for tus, non-usable for tus—Non-usable for different purposes different purposes different purposes as (other than military (other than military) a barrier, sometimes temporary useful for gardening architecture) after first use (O3) Preliminary ter- Apparatus which does Apparatus which does Apparatus which ritorial equipment and not need any territorial not need any territorial does not need any possible minor equipment equipment territorial equipment requirements for territorial infrastructures (O4) Availability of Additional apparatus Additional apparatus Additional apparatus materials and addi- available in real time available in real time not available in real tional apparatus from normal suppliers from specialist time suppliers (O5) Removability Apparatus leaving Apparatus leaving Light apparatus and induced residual considerable residuals considerable residuals (heavy when wet) environmental impact leaving no residuals (fully removable) (continued) 156 9 Temporary Flood Proofing Devices Analysis

9.2.2 C.R.2 (Floodwalls Removable Group 2): Supportive/ Juxtaposed Use of Fluid Containers

This group includes the use of barriers made of fluid containers like modular tubes or containers to be filled with air or water (acting as temporary barriers). It is the second category of flood proofing techniques to be presented in our work, and it refers to measures whose elements can also act individually against water; otherwise, more frequently, these can be juxtaposed and be used to form quite long defence lines. Compared to an equally long barrier unit of the previous class, the amount of base units is nearly always lower. These elements are able to withstand water action in different ways, whether they be filled with air or liquids (generally water). They all benefit from the waterproofing properties of the plastic materials they are made of, but they oppose the water pressure 9.2 Description of Temporary Flood Proofing Proposed Classes 157 in different ways. In the former case, i.e. using air-filled containers, they manage to anchor the line to the ground through different mechanisms by using base weights as part of the cladding material and/or gravity, once again, as it is placed on floodwater (e.g. connecting to strips positioned in front of the dike that are topped and overloaded by flood water). In the latter case, i.e. water-filled containers, they use the gravity placed on the water masses they are filled with and/or some purpose-built pulling elements which may be pegged down to the ground and/or tied to one another. These solutions are generally less heavy than the previous group, yet their surface areas are quite voluminous when operational—whereas they are much less bulky and/or very light during transport operations, since they are folded and empty.

9.2.2.1 C.R.2.1: Air-Filled Containers (Inﬂatable/Flexible)

This solution opts for using tubes that are made of flexible plastic materials and are filled with air by means of a compressor once they are positioned on the defence line—it is therefore advisable to assess that a power supply is available near the area where the system is laid to make sure the socket type matches the compressor’s plug or otherwise a power generator could be used. All tubes can be connected to each other so as to form long defence lines. Their surface area can be bigger than their diameter due to some necessary elements anchoring the structure to the ground (for instance “automatically”, by the own weight of the flood water), a vital measure to avert floating. They are a fully mobile, relatively lightweight (in several cases they can be transported in bags by operators working in pairs) and rapidly deployable option, which makes them particularly suitable for inner or intermediate defence lines controlled by a low number of trained operators. Hence, as provided for by a temporary flood proofing response plan, like other techniques they can be part of a ‘reserve unit’ whose aim is to intervene in case any unexpected event occurs to the defence system. Their use involves drawing polygons on the ground corresponding to the defence lines (namely joining straight segments) where the individual parts of the barrier is to be placed. There is certainly no other way for these elements to bypass obstacles, since once inflated they cannot be bent or curved on account of their poor plasticity and deformability of shape. The operational use requires paying special attention to the contours of the laying grounds as well as to constantly monitoring their pressure according to the different weather and atmospheric temperatures (especially between night and day). The following Table 9.2 (at the end of this paragraph) shows a detailed schematisation of the abovementioned characteristics in comparison to the distinguishing factors that have been determined to choose among temporary flood proofing techniques. Figure 9.10 indicatively shows ways to use this kind of techniques (Fig. 9.11). 158 9 Temporary Flood Proofing Devices Analysis

Fig. 9.10 Air ﬁlled containers: transverse section (by way of an example—drawing not in scale)

Fig. 9.11 A couple of representative examples of air ﬁlled containers technique

9.2.2.2 C.R.2.2: Water-Filled Containers (Tenders/Flexible)

In a comparison to the previous solution, these particular tubes are also made of flexible plastic materials, yet for filling operations they need water and pumps instead of air-compressors.3 Hence, they are particularly fitting for advanced

3Despite their ability to protect long spans with a single section, some products available on the market demand to undergo a pre-tensioning phase by means of an air-compressor before being ﬁlled 9.2 Description of Temporary Flood Prooﬁng Proposed Classes 159

Fig. 9.12 Water ﬁlled containers: transverse section (by way of an example—drawing not in scale)

(or intermediate) defence lines, which are close to water, or even for lines that are in the vicinity of basins or lake shores. Besides, this measure generally needs its ground anchoring to be simpler and less continuous (accomplished by some pulling elements), since the dike does not risk moving. In addition, on equal heights, it usually covers a smaller surface area than air-filled tubes. Given their ability to avoid floating, then, they can also be placed side by side to form a double line, or otherwise be overlapped to form another structure with a triangular section, as it occurs with sandbags, by laying a third tube between the bottom ones—or even with three bottom tubes, two in between and one on the top (obviously, being each tube fastened to the others—see Figs. 9.12 and 9.13). These containers are heavier than the previous ones, so they can withstand a higher water flow velocity. Furthermore, water weight enables the tubes to form defence lines that sometimes are not drawn with polygon segments, like in the previous case, thus being better adaptable in shape to overcome small obstacles and sharp surfaces. As a result, individual parts are often very long, that is several tens or even hundreds of metres. On account of the size and heaviness of the barriers, the installation of such measure is slightly slower, yet a bit more demanding from a technical point of view. Table 9.2 shows a detailed schematisation of the abovementioned characteristics in comparison to the distinguishing factors that have been determined to choose among temporary flood proofing techniques. Figure 9.12 indicatively shows ways to use this kind of techniques.

with water in order to ensure a correct positioning into the defence line, hard to be changed when full. 160 9 Temporary Flood Prooﬁng Devices Analysis

Fig. 9.13 A selection of representative examples of water-ﬁlled containers technique

9.2.2.3 C.R.2.3: Rigid Water Containers (Pluggable)

This solution consists of tanks, drums and jerry cans that are made of waterproof, rigid and self-supporting plastic. Their purposely-built shaping permits them to be filled with water, or by means of pumps (but no specific pressure is needed) or through self-filling holes (on the flood water face), and secured to each other, so that all connections become watertight. At a later stage, they are often tied to one another, and sometimes anchored to the ground. Their surface area is significant, also when empty, so they require a good amount of (open-air, if need be) storage areas (when not operational) and means of transport to get to the defence line (but sometimes they are openable and consequently stackable to save space). Nonetheless, they are 9.2 Description of Temporary Flood Proofing Proposed Classes 161

Fig. 9.14 Transverse section (by way of an example—drawing not in scale) lightweight elements (except for some heavy components, to be added to guarantee the stability when water level is low, for the self-filling ones), suitable for stable, long- lasting and medium weight defence lines, be they advanced, intermediate or inner. In some cases, these containers can be stacked up to form sensibly high defence barriers, compared to the base surface area, and they can be covered with waterproof sheeting primarily on the water side in order to strengthen their water tightness. Such elements can be used for purposes other than flood proofing, e.g. traffic dividers, as well as vehicles or pedestrian barriers. Table 9.2 shows a detailed schematisation of the abovementioned characteristics in comparison to the distinguishing factors that have been determined to choose among temporary flood proofing techniques. Figure 9.14 indicatively shows ways to use this kind of techniques (Fig. 9.15).

9.2.2.4 C.R.2.4: Open Water Containers

This apparatus differs from the previous one since all components are generally unassembled as they get to the defence line. To put them into operation, not only is it necessary to consolidate but also to assemble them in the first place. For example, water tanks are manufactured from flexible plastic materials (waterproof liners) that are secured through their ends (edges) either to some steady, tubular metal structures or to thick, rolled-up sheets made of rigid plastic. As a result, the whole structure benefits from stability, adherence to the ground and an appropriate water capacity (acting in a similar manner of rapidly deployable earth-filled dikes described in section C.R.1.2). This group also includes portable cylinder flood barriers, as well as longer and sturdier versions of the above ground pools that are usually installed in gardens in summer time. These modules can be bigger than the previous ones, but they cannot be overlapped to form higher barriers. However, they can be transported more effectively and offer a greater amount of mass to withstand floods. For some versions, a single module is enough to cover and protect a limited span (e.g. driveways to 162 9 Temporary Flood Proofing Devices Analysis

Fig. 9.15 A selection of representative examples of rigid water containers technique industrial buildings or yards protected by waterproof perimeter walls). Despite their better performances in countering water flow, such measures need more time to be positioned in the line and a higher level of expertise to be assembled, though they involve smaller surface areas/volumes while being transported. The joint action of different modules is produced by the contact between liners or plastic elements, adhering to each other because of the water pressure placed on the containers, as much as by the supporting frameworks being secured together. Once again, the water side can be reinforced with waterproof sheets. Table 9.2 shows a detailed schematisation of the abovementioned characteristics in comparison to the distinguishing factors that have been determined to choose among the available temporary flood proofing techniques. Figure 9.16 approximately shows the ways of use of this kind of technique (Fig. 9.17). 9.2 Description of Temporary Flood Proofing Proposed Classes 163

Fig. 9.16 Transverse section of open water containers technique (by way of an example—drawing not in scale)

Fig. 9.17 A selection of representative examples of open water containers technique 164 9 Temporary Flood Prooﬁng Devices Analysis

Table 9.2 Air-filled, water-filled, rigid water and open water containers: SENSO model evaluation elements SENSO model factors Floodwalls Removable C.R.2—Supportive/juxtaposed use of Fluid Solution group containers Air-filled Water-filled Rigid water Open water containers containers containers containers Techniques (C.R.2.1) (C.R.2.2) (C.R.2.3) (C.R.2.4) Socio-economic context—(S) (S1) Available budget with regard to the area being protected 1. Procurement Medium Medium Medium Medium 2. Assembly/disas- Low Medium High High sembly, transport and clearance operations 3. Maintenance/ Low Low Medium to high Medium storage (when not in use) 4. Reusability High High High High (in more than in one flood event) 5. Alternative use Medium (artifi- Medium (artifi- High (artificial Medium (artificial water cial water water basins, oil cial water basins, oil spills) basins, oil spills, traffic basins, forest spills) dividers, pedes- fires fight) trian barriers, vehicle barriers) (S2) Timely availability of trained workforce and/or possible self-employment for private individuals 1. Specific training Low (only for a Medium (for the Low High (for all courses are few operators) group of (coordinators) operators) required operators) 2. Technical Low Low Medium (for the Low (generic) skills at a group of professional level operators) are required 3. Self-employment None None Rarely None is possible for private individuals (only short line of defense) 4. Automatic solu- None None None None tions do not involve workforce—except for regular scheduled maintenance and surveillance (S3) Availability of auxiliary means of transport and equipment (continued) 9.2 Description of Temporary Flood Proofing Proposed Classes 165

Table 9.2 (continued) SENSO model factors Floodwalls Removable C.R.2—Supportive/juxtaposed use of Fluid Solution group containers Air-filled Water-filled Rigid water Open water containers containers containers containers Techniques (C.R.2.1) (C.R.2.2) (C.R.2.3) (C.R.2.4) 1. Need for auxil- Need for light Need for light Need for heavy Need for heavy iary equipment or auxiliary equip- auxiliary equip- auxiliary equip- auxiliary equip- specific means of ment ment (water ment and/or spe- ment and/or transport (compressors) pumps) cific means of specific means transport (low of transport pressure water (low pressure pump; vehicles water pumps and round trips) and vehicles) Environment and event scenarios—(E) (E1) Performances in relation to water level h, flow velocity v and solid transport values—i.e. event scenarios Water level Moderate High From low to From low to very elevated elevated Flow velocity Low Moderate to Moderate From moderate rapida to rapid Solid transport and Low—sand or Low—sand or Medium—gar- Low—sand or floating materials suspended soil, suspended soil, bage containers, suspended soil, branches and branches and benches, tree branches and other light float- other light float- trunks, furni- other light ing materials ing materials tures (but pro- floating portionally to the materials water level) (E2) Extension and – Suitable for – Suitable for – Suitable for all – Suitable for type of span intermediate advanced and types of defence all types of (or spans) being (block or deflec- intermediate lines defence lines protected tion) and inner (block or – Suitable for all (except when an defence lines deflection) different lengths inner line forms – Suitable for all defence lines (yet longer than a closed ring) different lengths – Suitable for all sandbags at the – Suitable for (but not for the different lengths same time) all different too short ones) (yet longer than lengths (yet sandbags at the longer than same time) sandbags at the same time) (E3) Need for pre- Suitable for Suitable for Suitable for Suitable for liminary studies levelled and almost all types levelled and almost all types and site preparation empty hard of reasonably empty hard of reasonably depending on surfaces levelled and surfaces levelled and ground empty surfaces empty surfaces morphology (E4) Building Suitable to be Suitable to be Suitable to be Suitable to be types, from foun- used away from used away from used away from used away from dations to buildings. buildings buildings buildings and (continued) 166 9 Temporary Flood Proofing Devices Analysis

Table 9.2 (continued) SENSO model factors Floodwalls Removable C.R.2—Supportive/juxtaposed use of Fluid Solution group containers Air-filled Water-filled Rigid water Open water containers containers containers containers Techniques (C.R.2.1) (C.R.2.2) (C.R.2.3) (C.R.2.4) construction mate- suitable to be rials and urbaniza- used tion context of set/propped constructions against concrete or masonry buildings Field operations—(O) (O1) Speed of Time needed for Time for the Time for the Time for the installation and the installation installation installation installation deployment (performed by (made by two (made by two (made by two two workers workers with workers with workers with with the avail- available equip- available equip- available equip- able equipment) ment) of a ment) of a 20 lin- ment) of a of a barrier of 20 linear meter ear meter barrier 20 linear meter 20 Â 1m:<1h barrier of a level of a level of 1 m: barrier of a level of 1 m: 1–3h 1–3h(<1 h for of 1 m: 3–6h self filling) (O2) Potential Light mobile Light mobile Light mobile Heavy mobile reuse and apparatus, reus- apparatus, reus- apparatus, reus- apparatus, reus- multipurpose use able in different able in different able in different able in different floods and floods and floods and floods and usable for dif- usable for dif- usable for differ- usable for different purposes ferent purposes ent purposes ferent purposes (O3) Preliminary Apparatus Apparatus Apparatus which Apparatus territorial equip- which does not which does not does not need which does not ment and possible need any territo- need any terri- any territorial need any terri- minor requirements rial equipment torial equipment equipment torial equip- for territorial (except for (except for ment (except infrastructures securing securing for securing systems) systems) system) (O4) Availability of Additional Additional Additional appa- Additional materials and addi- apparatus avail- apparatus avail- ratus available in apparatus avail- tional apparatus able in real time able in real time real time from able in real time from specialist from specialist specialist from specialist suppliers suppliers suppliers suppliers (O5) Removability Light apparatus Light apparatus Light apparatus Light apparatus and induced resid- leaving no leaving no leaving no resid- leaving no ual environmental residuals (fully residuals (fully uals (fully residuals (fully impact removable) removable) removable) removable) (O6) Quality and Collapsible Collapsible Non-collapsible Collapsible quantity of storage apparatus apparatus apparatus apparatus areas, when not in requiring safe requiring safe (except for requiring safe use storage against storage against openable) storage against (continued) 9.2 Description of Temporary Flood Proofing Proposed Classes 167

9.2.3 C.R.3 (Floodwalls Removable Group 3): Self-Deploying or Self-Supporting Mobile Barriers

This third group includes self-inflating barriers and those based on reticular (or similar) light structures. Their action mechanism against floods principally stems from their design and not from the exploitation of solid materials or fluid substances incorporated in themselves as a weight or as a supporting action, except for the flooding water itself. Since they are fully mobile and often also easy to transport and assembly, these aspects make them competitive from several points of view, compared to many of the previous solutions (sandbags included). The materials in use include flexible fabrics that are manufactured from plastic, which is indeed the waterproof component of such barriers against water. A special design provides for a bearing structure that makes use of water weight and therefore gravity to adhere to the ground and avoid movement. Moreover, the incoming water pressure is used to stand and distribute the pressure itself on the bearing structure. In 168 9 Temporary Flood Proofing Devices Analysis general, measures belonging to this group are installed on relatively light defence lines with small ground surface areas (their ‘footprints’).

9.2.3.1 C.R.3.1: Self-Inﬂating Barriers

These barriers definitely act as sails, clearly pushed open and blown up by the incoming water rather than wind. Both water weight acting at the base and some pulling elements, connected to the bottom of a structure under water pressure, manage to hold against water a waterproof liner working as ‘sail’. When they are transported to the defence line by appropriate vehicles, the barriers are either rolled- up in bags, manageable by only two men, or placed on specific unrolling systems (in case of longer defence lines). Once they are positioned within the line, they keep adhering to the ground. Only when water arrives, the upper flap—the one expected to block water—is lifted by the stream flow or motion and opens itself like an envelope, whereas the lower flap is compressed by water and gravity, thus securing the barrier to the ground. Such option does not require any auxiliary systems to be installed, such as water pumps or air-compressors. Also, there is no need to transport heavy filling materials like sand or soil, nor to access water sources or provide for any equipment for the assembly operations, which makes these barriers extremely easy to position. Owing to the flexibility of their materials, such barriers have the advantage of being vehicle accessible (e.g. by emergency vehicles) from the opposite side of water. Besides, they can be easily modelled around possible obstacles and folded to form continuous defence lines having sudden, clear-cut changes of direction (even at right angles). Hence, as provided for by a temporary flood proofing response plan, like other techniques they can be an important component of a ‘reserve unit’ whose aim is to intervene in case any unexpected event occurs to the defence system. Nevertheless, such measures cannot withstand significant water heights and have very low resistance to floating or rolling materials in collision. Table 9.3 shows a detailed schematisation of the abovementioned characteristics in comparison with the distinguishing factors that have been determined to help in choosing among temporary flood proofing techniques. Figure 9.18 shows schematically the ways to use this kind of techniques (Fig. 9.19). 9.2 Description of Temporary Flood Proofing Proposed Classes 169

Fig. 9.18 Transverse section (by way of an example—drawing not in scale)

Fig. 9.19 A selection of representative examples of self-inﬂating barriers technique 170 9 Temporary Flood Prooﬁng Devices Analysis

9.2.3.2 C.R.3.2: Self-Supporting Barriers

These barriers are supported by structures made of joint metal beams, often designed in a reticular system, which act as ‘props’ or stay rods. Some metal meshes or plates are propped or secured or integrated to them, weighing directly on the base supporting structure. The supporting structures are triangular in shape (vertical section) and metal meshes or plates rest on or are secured to the superior side of the triangle that has been raised to hold flood water back. To ensure the water tightness of the barrier, these meshes or plates are often covered with waterproof plastic sheets that are tied to the metal structures. This triangular shape allows selecting from two main working mechanisms for such barriers: wedge action, in which water partially covers the barrier and pushes it to the ground, thus ensuring its horizontal firmness; the barrier is secured to the ground and therefore able to hold water back, as its height goes beyond water level. Compared to the former, the latter mechanism works basically on an inverse principle opting for a ‘L’-shaped design of the barrier section; the vertical side is made of resistant watertight plates and acts as a shield, whereas the horizontal side is also made of resistant watertight plates but is compressed by water, which ensures stability and a ground anchoring to the structure. Some stay rods or seal beads (or specific design solutions) are placed between the two ends of the ‘L’-shape, either to release or bear the bolt tensions (shear stress) which may generate in joining the two sides of the ‘L’. Individual units are designed to be laterally connected through purposely engineered watertight junctions, or otherwise are covered with watertight sheets. Such an option does not require any auxiliary systems to be installed such as water pumps or air-compressors. Also, there is no need to transport heavy filling materials like sand or soil, nor to access water sources to fill them. However, all parts need to be assembled, so their positioning is not as rapid as in the previous case. Besides, tools and appropriate training are needed so as to use them correctly. As far as land positioning is concerned, these barriers can work quite well—and better than the previous ones—on rough land in their reticular version, though not so well in the ‘L’ version; also, generally they do not suit possible important changes of direction (except some kind of ‘L’ version, being more geometrically or spatially adaptable on an even plain). 9.2 Description of Temporary Flood Proofing Proposed Classes 171

In spite of significant ground surface areas, this measure can get higher than the previous one and is more resistant to floating or rolling material in a collision. Table 9.3 shows a detailed schematisation of the abovementioned characteristics in comparison to the distinguishing factors that have been determined to choose among temporary flood proofing techniques. Figure 9.20 shows a couple of working mechanism of this kind of technique (Fig. 9.21).

Fig. 9.20 Self-supporting barrier working mechanisms transverse section (by way of an example—drawing not in scale) 172 9 Temporary Flood Prooﬁng Devices Analysis

Fig. 9.21 A selection of representative examples of self-supporting barriers technique 9.2 Description of Temporary Flood Prooﬁng Proposed Classes 173

Table 9.3 Self-inflating and self-supporting barriers: SENSO model evaluation factors SENSO model factors Floodwalls Removable C.R.3—Self-deploying or self- Solution group supporting mobile barriers Self-inflating barriers Self-supporting barriers Techniques (C.R.3.1) (C.R.3.2) Socio-economic context—(S) (S1) Available budget with regard to the area being protected 1. Procurement Low Low 2. Assembly/disassembly, Low Medium transport and clearance operations 3. Maintenance/storage (when Low Medium not in use) 4. Reusability (in more than in High High one flood event) 5. Alternative use Medium (artificial water Low basins, forest fires fight) (S2) Timely availability of trained workforce and/or possible self-employment for private individuals 1. Specific training courses are Low (only few operators Medium (for the group of required needed) operators) 2. Technical (generic) skills at Low Low a professional level are required 3. Self-employment is possible Yes None (except small L-shaped) for private individuals (only short line of defense) 4. Automatic solutions do not None None involve workforce—except for regular scheduled maintenance and surveillance (S3) Availability of auxiliary means of transport and equipment 1. Need for auxiliary equip- Need for specific means of Need for light auxiliary ment or specific means of transport—low (sometimes equipment (tools)—Need for transport one vehicle) specific means of transport Environment and event scenarios—(E) (E1) Performances in relation to water level h, flow velocity v and solid transport values—i.e. event scenarios Water level Very elevated (up to) Very elevated (up to) Flow velocity Moderate (up to) Moderate (up to) Solid transport and floating Low—sand or suspended soil, Low—sand or suspended soil, materials branches and other light float- branches and other light ing materials floating materials (E2) Extension and type of Suitable for all types of Suitable for all types of span (or spans) being protected defence lines defence lines Suitable for all different Suitable for all different lengths (yet longer than those lengths (yet longer than those (continued) 174 9 Temporary Flood Proofing Devices Analysis

Table 9.3 (continued) SENSO model factors Floodwalls Removable C.R.3—Self-deploying or self- Solution group supporting mobile barriers Self-inﬂating barriers Self-supporting barriers Techniques (C.R.3.1) (C.R.3.2) made of sandbags; same set- made of sandbags; same setting time) ting time) (E3) Need for preliminary Suitable for almost all types of Suitable for levelled and studies and site preparation reasonably levelled and empty empty hard surfaces (except depending on ground surfaces triangular shaped) morphology (E4) Building types, from Suitable to be used away from Suitable to be used away from foundations to construction buildings buildings (except the materials and urbanization L-shaped one, that is in some context of constructions case suitable to be set/propped against cultural heritage buildings) Field operations—(O) (O1) Speed of installation and Time for the installation (made Time for the installation deployment by two workers with available (made by two workers with equipment) of a 20 linear available equipment) of a meter barrier of a level of 1 m: 20 linear meter barrier of a <1h level of 1 m: 1–3h (O2) Potential reuse and Light mobile apparatus, reus- Light mobile apparatus, reus- multipurpose use able and usable for different able and usable for different purposes purposes (O3) Preliminary territorial Apparatus which does not Apparatus which does not equipment and possible minor need any territorial equipment need any territorial equipment requirements for territorial infrastructures (O4) Availability of materials Additional apparatus available Additional apparatus avail- and additional apparatus in real time from specialist able in real time from spe- suppliers cialist suppliers (O5) Removability and Light apparatus leaving no Light apparatus leaving no induced residual environmen- residuals (fully removable) residuals (fully removable) tal impact (O6) Quality and quantity of Collapsible apparatus requir- Collapsible apparatus requir- storage areas, when not in use ing safe storage against atmo- ing safe storage against atmospheric agents (protections spheric agents (metal against UV rays action) corrosion) (O7) Maintenance require- Apparatus non-reparable/non Apparatus non-reparable/non ments, operating times and replaceable on-site, requiring replaceable on-site, requiring potential repairs in case of frequent and regular frequent and regular damage, even when maintenance maintenance operational Usage variations None None 9.2 Description of Temporary Flood Prooﬁng Proposed Classes 175

9.2.4 C.R.4 (Floodwalls Removable Group 2): Emergency Dikes and/or Berms of Loose/Free Solid Material

The fourth group of flood proofing techniques takes into account heavy emergency measures, i.e. dikes made of loose or free solid materials, which only differ from structural and permanent defence measures for their quick planning phase, the lack of interaction with other measures within their intended operational area and a detail- oriented operational approach referring to medium to short-term actions. Indeed, it is a question of placing a sometimes-huge amount of solid materials into the defence lines to withstand water through their weight, the operational phase of which conceived under pressure during emergency situations. Once they become operational, such barriers are hardly removable due to the weightiness and quantity of used materials, which confers them the ability to counter even extraordinary flooding scenarios—a water level equal to several metres and a notable flow velocity. They are therefore more frequently used for advanced defence lines, although in some occasions they have been also used for ‘closed ring’ inner lines in the USA to protect individual buildings, whenever the event scenarios could count on warning procedures with long-range forecasts. In general, measures belonging to this group are installed on the heaviest defence lines with the largest ground contact areas (‘footprints’).

9.2.4.1 C.R.4.1: Earth Levees/Dikes

These are often substantial, weighty dikes which can be built for our purposes only with the aid of heavy earth-moving machines, which gather materials on the defence line to form sometimes remarkable levees in terms of height, width and length. Unlike permanent earth dikes, such levees are generally trapezoidal in shape and could not undergo any specific soil compaction processes. They certainly have no additional diaphragm wall, nor grassy or stony surfaces, crests, terracing or hydraulic systems to set or monitor the water level, whereas on the water side they are seldom wrapped with plastic sheets that aim at reducing the erosion produced by water action. Conversely, the upper surface of the levee can normally be used as a walkway by the operators for inspection purposes. Essentially, this option consists of additional temporary embankments whose function is to temporarily hold back high water volumes. Some dimensional ratios on their construction specify that the section base length should be set between five and seven times its height, and that the security coefficient related to the maximum expected level 176 9 Temporary Flood Proofing Devices Analysis

Fig. 9.22 Working mechanisms of earth dikes transverse section (by way of an example—drawing not in scale)

Fig. 9.23 A couple of representative examples of earth-dikes technique should be equal to 20% (1.2). Table 9.4 shows a detailed schematisation of the abovementioned characteristics in comparison to the distinguishing factors that have been determined to choose among temporary ﬂood prooﬁng techniques. Figure 9.22 shows ways of using this kind of techniques (Fig. 9.23).

9.2.4.2 C.R.4.2: Concrete/Stone/Heavy Materials Blocks

This option involves once again weighty dikes, yet made by using large stones or concrete blocks or heavy-recycled-material blocks, which may as well be substantial in size. 9.2 Description of Temporary Flood Prooﬁng Proposed Classes 177

As regards to the stability and water tightness of the barrier, however, their complexity grows together with the intended barrier height. Although such barriers can be erected with the aid of heavy machinery, the shape of individual components is crucial, since they are rigid instead of loose or distortable and they are characterized by a dry fix (no mortar) installation mechanism, under any weather condition. To solve such issues, at least partially, these barriers are sometimes wrapped with plastic sheets on the water side, which aims at minimising any leakages caused by water seeping through the gaps. Otherwise, they are coupled with earth-based strategies, so as to fill the gaps between the blocks. The problem still remains, but it is less significant when the blocks are laid on soft ground that is compressed by gravity and reshapes itself by adhering to the barrier—even though the ground can’t be too porous to keep its supporting properties when saturated—or when the blocks, more easily if made of concrete, are rectangular in shape. Despite some difficulties in use, above all when small leakages are acceptable, such barriers are amazing at holding back rapid water flows, which are characterised by a significant solid transport and even substantial floating materials (Fig. 9.24).

Fig. 9.24 Example of heavy block barrier dry ﬁx working mechanisms transverse section (by way of an example—drawing not in scale) 178 9 Temporary Flood Prooﬁng Devices Analysis

Table 9.4 shows a detailed schematisation of the abovementioned characteristics in comparison to the distinguishing factors that have been determined to choose among temporary ﬂood prooﬁng techniques. Figure 9.25 shows a typical way to use this kind of techniques.

Fig. 9.25 A selection of representative examples of concrete/stones/heavy materials blocks technique 9.2 Description of Temporary Flood Prooﬁng Proposed Classes 179

Table 9.4 Earth levees/dikes and concrete/stones/heavy materials blocks: SENSO model evaluation factors SENSO model factors Floodwalls Removable C.R.4—Emergency dikes and/or berms Solution group of loose solid material Concrete/Stones/heavy Techniques Earth levees/dikes (C.R.4.1) materials blocks (C.R.4.2) Socio-economic context—(S) (S1) Available budget with regard to the area being protected 1. Procurement Medium Medium 2. Assembly/disassembly, Very high High transport and clearance operations 3. Maintenance/storage (when Low Medium not in use) 4. Reusability (in more than in Low High one flood event) 5. Alternative use Low (in case, although rare, Low (vehicle barriers) lava flow) (S2) Timely availability of trained workforce and/or possible self-employment for private individuals 1. Specific training courses are Medium (a certain number of Medium (a certain number of required operators) operators) 2. Technical (generic) skills at Medium (a certain number of Medium (a certain number of a professional level are operators) operators) required 3. Self-employment is possible None None for private individuals (only short line of defense) 4. Automatic solutions do not None None involve workforce—except for regular scheduled maintenance and surveillance (S3) Availability of auxiliary means of transport and equipment 1. Need for auxiliary equip- Need for heavy auxiliary Need for heavy auxiliary ment or specific means of equipment and/or specific equipment and/or specific transport means of transport (mechani- means of transport (vehicles cal earth-movers and bulldozers) bulldozers) Environment and event scenarios—(E) (E1) Performances in relation to water level h, flow velocity v and solid transport values—i.e. event scenarios Water level High High Flow velocity Rapid Rapid Solid transport and floating – Heavy -cars, motorbikes and – Heavy cars, motorbikes and materials electrical appliances electrical appliances – Boulders (if rightly sized) – Ice and Debris flows (if rightly sized) (continued) 180 9 Temporary Flood Proofing Devices Analysis

Table 9.4 (continued) SENSO model factors Floodwalls Removable C.R.4—Emergency dikes and/or berms Solution group of loose solid material Concrete/Stones/heavy Techniques Earth levees/dikes (C.R.4.1) materials blocks (C.R.4.2) (E2) Extension and type of Suitable for all types of defence Suitable for all types of span (or spans) being protected lines although a remarkable defence lines footprint (having sufficient Suitable for all different room for manoeuvre) lengths (yet longer than Suitable for all different sandbags at the same time) lengths (yet longer than sandbags at the same time) (E3) Need for preliminary Suitable for almost all types of Suitable for levelled and studies and site preparation reasonably levelled and empty empty hard surfaces (if blocks depending on ground surfaces are squared) morphology Suitable for all grounds (having sufficient room for manoeuvre) (E4) Building types, from Suitable to be used away from Suitable to be used away from foundations to construction buildings buildings materials and urbanization context of constructions Field operations—(O) (O1) Speed of installation and Time for the installation (made Time for the installation deployment by two workers with available (made by two workers with equipment) of a 20 linear available equipment) of a meter barrier of a level of 1 m: 20 linear meter barrier of a 1–3h level of 1 m: 3–6h (O2) Potential reuse and Heavy mobile apparatus, reus- Heavy mobile apparatus, multipurpose use able and usable for different reusable and usable for dif- purposes ferent purposes (including temporary architecture) (O3) Preliminary territorial Apparatus which does not Apparatus which does not equipment and possible minor need any territorial equipment need any territorial equipment requirements for territorial infrastructures (O4) Availability of materials Additional apparatus available Additional apparatus avail- and additional apparatus in real time from normal able in real time from spe- suppliers cialist suppliers (O5) Removability and Apparatus leaving consider- Heavy apparatus leaving no induced residual environmen- able residuals residuals (fully removable) tal impact (O6) Quality and quantity of Non-collapsible apparatus Non-collapsible apparatus storage areas, when not in use requiring no safe storage requiring no safe storage against atmospheric agents against atmospheric agents (natural material) (except UV rays in case of heavy recycled plastic materials) (continued) 9.2 Description of Temporary Flood Proofing Proposed Classes 181

Table 9.4 (continued) SENSO model factors Floodwalls Removable C.R.4—Emergency dikes and/or berms Solution group of loose solid material Concrete/Stones/heavy Techniques Earth levees/dikes (C.R.4.1) materials blocks (C.R.4.2) (O7) Maintenance require- Apparatus reparable/non Apparatus non-reparable/non ments, operating times and replaceable on-site, requiring replaceable on-site, requiring potential repairs in case of frequent and regular sporadic and regular damage, even when maintenance maintenance operational Usage variations Plastic sheeting Plastic sheeting, soil to ﬁll the cracks (in case of non-squared blocks)

9.2.5 C.P.1 (Floodwalls Pre-arranged/Pre-located Group 1): Temporary Barriers/Shields with Especially Crafted Anchoring (Temporary Waterwalls)

The fifth group of temporary flood proofing techniques consists in water defence strategies that rely upon belting operations to protect an intended target. Unlike the four previous groups, these principally belong to another category, i.e. Pre- arranged/Pre-located techniques. In order to be activated, these latter strategies need to permanently arrange for the deployment of specific barriers within the defence line by changing the conditions of sites and constructions. Their countering action against water is not as ‘passive’ as permanent defence lines, yet involves an ‘active’ component that is only put into practice when the defence action is needed. Basically, these techniques manage to dam water flow or stop water seepage in advanced, intermediate and inner defence lines. They operate as barriers that are either ground-fixed (if not secured to vertical structures connected to foundations) or fitted retrospectively to existing securing systems, which are installed prior to warning notices that are issued in advance of a disaster by civil protection monitoring services. Such barriers typically utilise single modules as their defence elements, which can be juxtaposed or stacked one on top of the other even in vast numbers. These are wisely designed and arranged to work within the defence line area in specific, predetermined positions that cannot change during the event. Thus, their planning phase regularly demands a greater effort than removable techniques, yet compen- sating such ‘cost’ with generally better results in terms of tightness. In addition, the solutions belonging to this group are normally installed on defence lines characterised by a medium weightiness, but also by very low surface areas. 182 9 Temporary Flood Proofing Devices Analysis

9.2.5.1 C.P.1.1: Ground Anchored Temporary Barriers

These barriers are made of modular elements shaped as planks or elongated boards, which are generally manufactured from light and hollow alloys but sometimes also from glass (in case of special landscape conditions to be protected for quite long periods), and equipped with rubber seals at their ends. They are vertically (or slightly inclined, suitable in case of lower expected water levels) stackable according to varying numbers and heights (especially if made of metal alloys), and they can be fitted on vertical supporting beams that are ground (or base) anchored by means of existing fixing systems (e.g. bolts) and connected to foundations, which ensures stability to the defence line. Such anchoring systems are protected by covered sockets when not in use and support the connections keeping all barrier segments together. The barrier can be replicated into multiple ‘infill panels’, which in the case of metal alloys can reach up to several metres (yet normally less than 3–4 m; glass barriers, though, are normally shorter than 2 m). Concerning high water levels and flow velocities, the vertical supporting beams are engineered to work even on lower distances between the bearing structures and their anchor sockets—and their number on equal barrier lengths shall raise accordingly. If the vertical beams cannot be supported by walls, for instance, they can be reinforced with appropriate push-pull props or support frames on the opposite side of the water in order to improve tightness against horizontal pressure. Moreover, if the supporting beams are properly selected and configured, this measure enables defence lines to be erected by fitting in with any shaping requirements (on separate modules), so that changes of directions can be available for specific angles (mostly perpendicular). As regards to the metal alloy version, not only do these barriers utilise suitable seals, but also screw closing and fixing systems on top of the supporting beams in some cases, so as to ensure tightness against any water seepage between the boards, while in other cases some hollow boards are designed to be permeated by water. Both measures are intended to gain a vertical force and make the gaps tight enough to withstand water action. The evaluation of an event scenario is vital also to use such a technique correctly. Supposing that a calculation for water height is rounded down after considering the maximum barrier level, the barrier itself could not be raised or extended anymore during the flood event if water ever happened to circumvent the defence line. This is mainly due to the fact that no anchoring can be added in real time—since their arrangement is to be accomplished during the territorial equipment phase of the preparatory period, see Chap. 8. Conversely, in case of need, such barriers can be reinforced mainly being propped by weighty elements which may increase their tightness to horizontal pressure (sandbags, concrete blocks and so on). A variant of this technique is based on a vertical scheme of metal modules which are set in sealed close contact to each other and anchored to the ground on a prepared concrete foundation equipped with anchor profiles which are designed with alter- nated angles (for instance 22.5 to the ideal defense line). This scheme allows to 9.2 Description of Temporary Flood Proofing Proposed Classes 183 obtain barriers vertically based on single modules, well-sealed, quickly to be positioned, but heavier to be managed. During a warning period, assembly operations concerning such barriers demand all permanently fixed constructions to be already thoroughly designed and installed within the defence line. Furthermore, they imply that workers should have technical expertise and materials should be stored with the utmost care in the interval between two events, in order to avoid damaging or losing part of the components of the structure and therefore to ensure both reusability and reasonably quick installation times. Transport times on advanced, intermediate and inner lines, as well as organisational and storage issues can sometimes be solved through appropriate barrier storage sites. Especially in this case when barriers are pre-arranged/pre-located, a convenient idea of appropriate storage could be the choice of a site near the defence line—better if concealed or integrated in urban design (for instance: bench box storage seats, wall racks, etc. see Fig. 9.26)—during the territorial equipment phase of the preparatory period initiated by civil protection activities. Logically, such a logistic choice, could be useful also in case of barrier being part of other groups of our classification. Table 9.5 shows a detailed schematisation of the abovementioned characteristics in comparison to the distinguishing factors that have been determined to choose among temporary flood proofing techniques. Figure 9.27 shows schematically a way to use this kind of techniques (Fig. 9.28).

9.2.5.2 C.P.1.2: Detachable Flood Gates

Compared to base-anchored temporary barriers previous group, these gates are generally made of higher single panels—namely with a smaller base; this means a different height ratio, namely more vertical. They sometimes are manufactured from wood or heavier plastic or metal materials, which only provide for lateral ﬁttings (anchors or grooves) consolidating the permanent structures within the defence line, yet not for foundations or bolting, in order to be used. Therefore, they require a quicker planning phase and less signiﬁcant operations of territorial equipment. In

Fig. 9.26 A couple of examples of appropriate storage choices near the defence line 184 9 Temporary Flood Prooﬁng Devices Analysis

Fig. 9.27 Ground anchored temporary barrier technique transverse sections (by way of an example—drawing not in scale) general, such measures imply a quicker and easier installation during the warning period and are usually cheap notwithstanding some low performances concerning tightness and maximum water levels, principally in long defence lines. Weightier solutions—made of either iron-based alloys or waterproofed solid wood—are not as quick in terms of installation, but they offer improved resistance to solid transport and floating materials in collision. In case of need, once again, this technique can be reinforced, namely being propped by weighty elements which may increase their tightness to horizontal pressure (sandbags, concrete blocks and so on). Besides, when necessary it can be useful to wrap the water side of long lines with plastic sheets—regardless of whether they are advanced (rarely) or intermediate lines (for instance operating in lines based on fence walls or between buildings). Since flood gates are fully detachable, such measures are ideal for protecting building entrances and openings, as well as properties surrounded by watertight perimeter walls where doors, gates and access ways need an alternative to watertight 9.2 Description of Temporary Flood Proofing Proposed Classes 185

Fig. 9.28 A selection of representative examples of ground anchored temporary barriers technique 186 9 Temporary Flood Prooﬁng Devices Analysis

flood gates (cf. next paragraph)—which are permanently fixed to the structures, thus having a physical (volumetric and spatial) and aesthetic impact, even when open. Only those gates installed to close specific openings can be stackable and therefore stand for a real exception, that is a middle ground solution between them and the barriers shown in C.P.1.1. Similarly, the gates made of light metal alloys are a peculiar case of single- shutter C.P.1.1, distinguishable from that because of the attaching/detaching system to face water pressure is principally based on permanent lateral/vertical elements. In this case too a convenient idea of appropriate storage could be the choice of a site near the defence line, as in the previous case. Table 9.5 shows a detailed schematisation of the abovementioned characteristics in comparison to the distinguishing factors that have been determined to choose among temporary flood proofing techniques. Figure 9.29 shows a classic way to use this kind of techniques (Fig. 9.30).

Fig. 9.29 Example scheme of detachable ﬂood gate, front view (by way of an example—drawing not in scale)

Fig. 9.30 A couple of representative examples of detachable ﬂood gates technique 9.2 Description of Temporary Flood Prooﬁng Proposed Classes 187

Table 9.5 Ground-anchored temporary barriers and detachable flood gates: SENSO model evaluation factors SENSO model factors Floodwalls Pre-arranged/Pre-located C.P.1—Temporary Solution group barriers/shields with especially crafted anchoring Ground-Anchored temporary Detachable flood gates Techniques barriers (C.P.1.1) (C.P.1.2) Socio-economic context—(S) (S1) Available budget with regard to the area being protected 1. Procurement High Medium 2. Assembly/disassembly, Medium Low transport and clearance operations 3. Maintenance/storage (when Medium Low not in use) 4. Reusability (in more than in Medium Low one flood event) 5. Alternative use None None (S2) Timely availability of trained workforce and/or possible self-employment for private individuals 1. Specific training courses are High (all operators) High, if installation is orga- required nized as a service Low in case of self- employment 2. Technical (generic) skills at High High, if installation is orga- a professional level are nized as a service required Medium in case of self- employment 3. Self-employment is possible None High for private individuals (only short line of defense) 4. Automatic solutions do not None None involve workforce—except for regular scheduled maintenance and surveillance (S3) Availability of auxiliary means of transport and equipment 1. Need for auxiliary equip- Medium (generic equipment Need for specific means of ment or specific means of and vehicles) transport (more than those transport related to the surveillance personnel), except the case of self-employment Environment and Event Scenarios—(E) (E1) Performances in relation to water level h, flow velocity v and solid transport values—i.e. event scenarios Water level High From Low to moderate Flow velocity Moderate Low Solid transport and floating Medium—garbage containers, Low—sand or suspended materials benches, tree trunks, furni- soils, branches and other light ture—Moderate floating materials—Low (continued) 188 9 Temporary Flood Proofing Devices Analysis

Table 9.5 (continued) SENSO model factors Floodwalls Pre-arranged/Pre-located C.P.1—Temporary Solution group barriers/shields with especially crafted anchoring Ground-Anchored temporary Detachable flood gates Techniques barriers (C.P.1.1) (C.P.1.2) (E2) Extension and type of Suitable for all types of Suitable for all types of span (or spans) being protected defence lines defence lines (except for Suitable for all different rings) lengths (yet longer than sand- Suitable for short lengths (yet bags at the same time) longer than sandbags at the same time) (E3) Need for preliminary Suitable for levelled and Suitable for levelled and studies and site preparation empty hard surfaces, to be empty hard surfaces, to be depending on ground selected or pre-pared (tech- selected or pre-pared (tech- morphology niques apt to work only on niques apt to work only on hard, flat and reasonably hard, flat and reasonably smooth surfaces—asphalt, smooth surfaces—asphalt, concrete, etc.) concrete, etc.) (E4) Building types, from Suitable to be used away from the more suitable to be used foundations to construction buildings set/propped against every materials and urbanization kind of buildings (wood or context of constructions light buildings included; crawlspace foundations excluded); Field operations—(O) (O1) Speed of installation and Time for the installation (made Time for the installation deployment by two workers with available (made by two workers with equipment) of a 20 linear available equipment) of a meter barrier of a level of 1 m: 20 linear meter barrier of a from 1–3h level of 1 m: <1h (O2) Potential reuse and Non-mobile apparatus, Non-mobile apparatus, multipurpose use non-usable for different non-usable for different purposes purposes (O3) Preliminary territorial Apparatus requiring ‘heavy’ Apparatus requiring ‘light’ equipment and possible minor territorial equipment territorial equipment or requirements for territorial building arrangements infrastructures (O4) Availability of materials Additional apparatus not Additional apparatus not and additional apparatus available in real time available in real time (O5) Removability and Heavy apparatus leaving no Apparatus inducing reduced induced residual environmen- residuals (fully removable, permanent changes to tal impact except for anchor pins) premises (O6) Quality and quantity of Non-collapsible apparatus Removable apparatus requir- storage areas, when not in use requiring safe storage against ing safe storage against atmospheric agents (corrosion atmospheric agents (corrosion of sealing rings and compres- and wear and tear of com- sion seals) pression seal) (continued) 9.2 Description of Temporary Flood Proofing Proposed Classes 189

9.2.6 C.D.1 (Floodwalls Demountable Group 1): Fixed Retractable Barriers

This group includes permanently fixed but mobile in place barriers, since hinged and therefore retractable and self-stored acting individually as gates or shields to defend singles spans. As anticipated, such solutions prove to be partially permanent and may also be referred to as semi-permanent. They all benefit from the waterproofing properties of the materials they are generally made of (light, even though often metallic), and they oppose the water pressure in the same manner, exploiting mechanical junction. These solutions do not need transport operations, since they are “always on line”, ready to be operational when necessary.

9.2.6.1 C.D.1.1: Watertight Openable Flood Gates

When vehicle or pedestrian access ways happen to become preferential waterways of the flood in an urban context or flood pathways, being in the vicinity of water, the construction of permanent watertight flood gates can be a simple and valid solution that is capable of stunning performances in withstanding flooding, whether they involve rivers, lakes or seas, and operate in advanced, intermediate or inner lines. From a technical point of view, this option is the most self-explanatory of all the techniques that have been analysed in this work. Essentially, they are solid, water- damming, single or double-shutter outdoor gates—usually made of relatively heavy materials—which are side (therefore laterally) hinged (pivoted) and designed for great tightness (but only on three sides, excluding the one on the top) through suitable gaskets or purpose-built compression seals. Compared to the previous measures, they sometimes offer lower water tightness performances since junction and sealing materials are clearly exposed to wear and 190 9 Temporary Flood Proofing Devices Analysis tear, even when they are subject to regular maintenance. Still, they can be triggered in no time by a single operator, by push button or occasionally by automated systems working together with water level sensors (solution to be precautionally coupled with a manual one, for a safe redundancy). Moreover, it goes without saying that they also keep working as ordinary gates, even though they need to be adequately signalled for their particular use and undergo regular maintenance by qualified personnel to assess their functioning correctly, as well as having to be constantly monitored during a flood event. Table 9.6 shows a detailed schematisation of the abovementioned characteristics in comparison to the distinguishing factors that have been determined to choose among temporary flood proofing techniques. Figure 9.31 shows, in a simplified manner, a way to use this kind of techniques (Fig. 9.32).

9.2.6.2 C.D.1.2: Retractable Self-Stored Flood Barriers

In this case, flood barriers (shields) or modular systems are integrated or recessed within the structures or paving throughout the defence line, being permanently on site, ready to deploy 24/7, 365 days a year, allowing a “near-instant”/very short deployment just prior to the threat of flood. Mostly placed in public open spaces, they generally move vertically and they are either deployed automatically (self- deploying fixed barriers) by means of hydro-pneumatic or electrical systems (triggered by Archimedes’ upward buoyant force of water or through suitable flood level sensors), semi-automatically (push-button operated by personnel in charge, taking full control of the barrier from remote location) or mechanically/manually in short times (also as redundancy option).

Fig. 9.31 Example scheme of openable ﬂood gate, front view (by way of an example—drawing not in scale) 9.2 Description of Temporary Flood Prooﬁng Proposed Classes 191

Fig. 9.32 A selection of representative examples of watertight openable ﬂood gates technique

This is the most varied group of measures, which namely includes: integrated inflatable systems on top of masonry embankments; mobile flood gates recessed under vehicle entrances; flip-up flood barriers recessed in paving; self-activating barriers; innovative floating lock system airbricks and so on. Such systems have many benefits as they do not need to be stored in warehouses, transported or mounted (“zero operational costs”)—in spite of a certain cost increase for their procurement, installation and maintenance—and they require no significant number of personnel to assemble/dismantling them, but only those operators in charge of supervising the correct deployment in case of need (being also possible the case of fully passive deployment, asking for no human action and no power). Nonetheless many times they need to be signalled for their peculiar presence and must undergo regular and accurate maintenance by qualified personnel to assure 192 9 Temporary Flood Proofing Devices Analysis their correct functioning, as well as having to be constantly monitored during a flood event. Furthermore, generally they cannot be stolen, as probably happened in the case of the tar-coated wooden gates missing along the bank of Arno river in Pisa in February 2014. Table 9.6 shows a detailed schematisation of the abovementioned characteristics in comparison to the distinguishing factors that have been determined to choose among temporary flood proofing techniques. Figure 9.33 shows, in a simplified manner, a few ways to use this kind of techniques (Fig. 9.34).

Fig. 9.33 A selection of schemes of working mechanism of ﬁxed retractable barriers, transverse section (by way of an example—drawing not in scale) 9.2 Description of Temporary Flood Prooﬁng Proposed Classes 193

Fig. 9.34 A selection of representative examples of retractable self-stored ﬂood barriers technique 194 9 Temporary Flood Prooﬁng Devices Analysis

Table 9.6 Watertight openable flood gates and retractable self-stored flood barriers: SENSO model evaluation factors SENSO model factors Solution group Floodwalls Demountable C.D.1—Fixed retractable barriers Watertight openable flood Retractable self-stored flood Techniques gates (C.D.1.1) barriers (C.D.1.2) Socio-economic context—(S) (S1) Available budget with regard to the area being protected 1. Procurement High High 2. Assembly/disassembly, None Low transport and clearance operations 3. Maintenance/storage (when None None not in use) 4. Reusability (in more than in High High one flood event) 5. Alternative use Low (as gates) None (S2) Timely availability of trained workforce and/or possible self-employment for private individuals 1. Specific training courses are None None required 2. Technical (generic) skills at None None a professional level are required 3. Self-employment is possible Yes Yes for private individuals (only short line of defense) 4. Automatic solutions do not Yes Yes involve workforce—except for regular scheduled maintenance and surveillance (S3) Availability of auxiliary means of transport and equipment 1. Need for auxiliary equip- 4. No need for auxiliary 4. No need for auxiliary ment or specific means of equipment or specific means equipment or specific means transport of transport of transport Environment and event scenarios—(E) (E1) Performances in relation to water level h, flow velocity v and solid transport values—i.e. event scenarios Water level High From low to elevated Flow velocity Moderate Moderate Solid transport and floating Medium—garbage con- Medium—garbage con- materials tainers, benches, tree trunks, tainers, benches, tree trunks, furniture (depending on gate furniture sizes) (E2) Extension and type of Suitable for all types of Depending on the design, span (or spans) being protected defence lines (except for generally rings) Suitable for all types of Suitable for short lines defence lines (except for (continued) 9.2 Description of Temporary Flood Proofing Proposed Classes 195

Table 9.6 (continued) SENSO model factors Solution group Floodwalls Demountable C.D.1—Fixed retractable barriers Watertight openable flood Retractable self-stored flood Techniques gates (C.D.1.1) barriers (C.D.1.2) rings) Suitable for all different lengths (yet longer than sandbags at the same time) (E3) Need for preliminary Suitable for hard, completely Depending on the design, studies and site preparation levelled, smooth and empty generally depending on ground surfaces Suitable for every kind of hard morphology surfaces (problems solved in the design phase of integration in the structure) (E4) Building types, from The more suitable to be used The more suitable to be used foundations to construction set/propped against concrete set/propped against concrete materials and urbanization or masonry buildings or masonry buildings context of constructions Suitable to be used away from Suitable to be used away from buildings buildings Field operations—(O) (O1) Speed of installation and Time for the installation Time for the activation (made deployment (made by two workers with by two workers with available available equipment) of a equipment) of a 20 linear 20 linear meter barrier of a meter barrier of a level of 1 m: level of 1 m: <1h <1h (O2) Potential reuse and Non-mobile apparatus, Non-mobile apparatus, multipurpose use non-usable for different pur- non-usable for different purposes (except as gates) poses (except as gates) (O3) Preliminary territorial Apparatus requiring ‘heavy’ Apparatus requiring ‘heavy’ equipment and possible minor territorial equipment territorial equipment requirements for territorial infrastructures (O4) Availability of materials Additional apparatus not Additional apparatus not and additional apparatus available in real time available in real time (O5) Removability and Apparatus inducing reduced Apparatus inducing signifi- induced residual environmen- permanent changes to cant permanent changes to tal impact premises premises (O6) Quality and quantity of Visible apparatus stored in Fold-up apparatus stored in storage areas, when not in use (along) the defence line (along) the defence line (O7) Maintenance require- Apparatus non-reparable/non Apparatus non-reparable/non ments, operating times and replaceable on-site, requiring replaceable on-site, requiring potential repairs in case of frequent and regular frequent and regular damage, even when maintenance maintenance operational Usage variations Sandbags or concrete blocks / (propped against back side) Plastic sheets (wrapping front side) 196 9 Temporary Flood Proofing Devices Analysis

9.2.7 D.R.1 (Dry Flood Prooﬁng Removable Group 1): Full Dry Flood Prooﬁng of Buildings

This seventh group includes such measures as the wrapping of vertical walls or with waterproof sheets or covering them with waterproof shields. These options consist in emergency operations that are exclusively performed on inner defence lines, as they directly cover the whole external perimeter of buildings exposed to water action. Such a technique is suitable for buildings whose external walls are deemed as fairly vulnerable to water action, mainly when flood waters are likely to recede very slowly. This is the case of walls made of lightweight, porous or partially permeable materials—e.g. wooden boards, plasterboard, sandstone and so on. Among other ‘ring’ strategies this group has the lowest perimeter, being in direct contact with the building itself, even though it maximises the disadvantage of isolating a building from the surrounding land and any human interaction with the community in the event of a flood. The solutions belonging to this group are generally installed on light defence lines. However, they have very limited surface areas and can hold back even significant water heights, as long as the structure can withstand water pressure or any water seepage at the bottom of the building. According to the potentially large and complex surfaces of external walls, the installation time for such defence lines may be rather long, so these measures are preferably set up in contexts where the warning system might ensure sufficient operational time.

9.2.7.1 D.R.1.1: Wrapping

This technique entails the perimeter of the external walls of the building to be protected, sometimes reaching remarkable heights (up to 3–4 m), since the building is wholly wrapped with waterproof cladding or plastic sheets. These latter coverings are secured to the building above (and/or supported by poles or props, as well as by metal or wooden plates) and to the ground below them, often by digging small trenches into the ground surrounding the whole perimeter, where the sheets are laid and to be covered with heavy materials (e.g. sandbags) in order to ensure water tightness. Behind the covering sheets, at the corner between the ground and the external walls of the building, a perforated drainage pipe is often placed to receive any water leakage that might gather or drain along the walls—from the building 9.2 Description of Temporary Flood Proofing Proposed Classes 197 section above the waterproof wrapping—even in the event of overflowing waves or bottom seepage (in the latter cases, the piping system can be connected to small water pumps). The wrapping technique, of course, requires the buildings walls to withstand the force produced by hydrostatic and water flow pressures. After being wrapped the building can be accessed, with the lowering of water, only coming from the outside, otherwise part of the waterproof covering would be ruined, which is why in such cases the building is usually evacuated before being sealed. Table 9.7 shows a detailed schematisation of the abovementioned characteristics in comparison to the distinguishing factors that have been determined to choose one or the other among temporary flood proofing techniques. Figure 9.35 shows, in a simplified scheme, the way to use this kind of technique (Fig. 9.36).

Fig. 9.35 Working mechanism of wrapping technique, transverse section (by way of an example—drawing not in scale) 198 9 Temporary Flood Prooﬁng Devices Analysis

Fig. 9.36 A couple of representative examples of wrapping technique

9.2.7.2 D.R.1.2: Packing

Packing shows another version of flood shields, that are propped up against a building, and another form of covering the building perimeter, as in the case of wrapping plastic sheets, as illustrated above. It varies from this latter technique for its solidity, even though this implies greater costs as well as more complex assembling and larger spaces of storing for the structures. However, thanks to its modularity, it allows installing specific modules for the openings, namely building entrances, in order to ensure their accessibility just before and after a flooding (not as it occurs) without compromising the functionality and potential reuse of barriers. It is basically a question of building a ‘closed ring’ (or part of it) defence line by propping heavy watertight shields against the building, whose walls will support most of the horizontal water pressure, as in the previous case, although some of it could be released on the barrier (especially in the case of perimeters made of glass). Shields are engineered to have watertight gaps between them. They can be placed vertically and propped up against the building to better unload part of the weight onto the ground, for example, by means of push-pull props. Table 9.7 shows a detailed schematisation of the abovementioned characteristics in comparison to the distinguishing factors that have been determined to choose among temporary flood proofing techniques. Figure 9.37 shows, in a simplified manner, a way to use this kind of technique (Fig. 9.38). 9.2 Description of Temporary Flood Proofing Proposed Classes 199

Fig. 9.37 Working mechanism of packing technique, transverse section (by way of an example—drawing not in scale)

Fig. 9.38 A selection of representative examples of packing technique 200 9 Temporary Flood Prooﬁng Devices Analysis

Table 9.7 Wrapping and packing techniques: SENSO model evaluation factors SENSO model factors Dry Flood Proofing Removable D.R.1—Full dry flood proofing Solution group of buildings Techniques Wrapping (D.R.1.1) Packing (D.R.1.2) Socio-economic context—(S) (S1) Available budget with regard to the area being protected 1. Procurement Medium High 2. Assembly/disassembly, Low Medium transport and clearance operations 3. Maintenance/storage (when Medium High not in use) 4. Reusability (in more than in Low High one flood event) 5. Alternative use None Low (security) (S2) Timely availability of trained workforce and/or possible self-employment for private individuals 1. Specific training courses are Yes—High Yes—High required 2. Technical (generic) skills at Yes—Low Yes—High a professional level are required 3. Self-employment is possible Yes Yes for private individuals (only short line of defense) 4. Automatic solutions do not None None involve workforce—except for regular scheduled maintenance and surveillance (S3) Availability of auxiliary means of transport and equipment 1. Need for auxiliary equip- Need for auxiliary equipment: Need for auxiliary equipment: ment or specific means of ladders, sandbags, drainage ladders, screwing operations transport pipes, etc. Environment and event scenarios—(E) (E1) Performances in relation to water level h, flow velocity v and solid transport values—i.e. event scenarios Water level High Moderate Flow velocity From low to moderate Moderate Solid transport and floating Low—sand or suspended Medium—garbage con- materials soils, branches and other light tainers, benches, tree trunks, floating materials furniture (E2) Extension and type of Ideal for rings Ideal for rings span (or spans) being protected Suitable for short lengths Suitable for short and medium lengths (E3) Need for preliminary Suitable for almost all types of Suitable for levelled and studies and site preparation reasonably levelled and empty empty hard surfaces to be depending on ground surfaces to be selected or selected or prepared morphology prepared (continued) 9.2 Description of Temporary Flood Proofing Proposed Classes 201

Table 9.7 (continued) SENSO model factors Dry Flood Proofing Removable D.R.1—Full dry flood proofing Solution group of buildings Techniques Wrapping (D.R.1.1) Packing (D.R.1.2) (E4) Building types, from The more suitable to be used The more suitable to be used foundations to construction set/propped against concrete or set/propped against every materials and urbanization masonry buildings; kind of buildings (wood or context of constructions light buildings included; crawlspace foundations excluded) Field operations—(O) (O1) Speed of installation and Time for the activation (made Time for the activation (made deployment by two workers with available by two workers with available equipment) of a 20 linear equipment) of a 20 linear meter barrier of a level of 1 m: meter barrier of a level of 1 m: 6–12 h 6–12 h (O2) Potential reuse and Light mobile apparatus, Heavy mobile apparatus, multipurpose use non-usable for different non-usable for different purposes purposes (O3) Preliminary territorial Apparatus which does not Apparatus which does not equipment and possible minor need any territorial equipment need any territorial equipment requirements for territorial infrastructures (O4) Availability of materials Additional apparatus not Additional apparatus not and additional apparatus available in real time available in real time (O5) Removability and Light apparatus leaving no Heavy apparatus leaving no induced residual environmen- residuals (fully removable) residuals (fully removable) tal impact (O6) Quality and quantity of Fold-up apparatus stored in Collapsible apparatus requir- storage areas, when not in use (along) the defence line ing safe storage against atmospheric agents (O7) Maintenance require- Apparatus non-reparable/non Apparatus non-reparable/non ments, operating times and replaceable on-site, requiring replaceable on-site, requiring potential repairs in case of frequent and regular frequent and regular damage, even when maintenance maintenance operational Usage variations Drainage pumps and external Push-pull props props 202 9 Temporary Flood Proofing Devices Analysis

9.2.8 D.P.1 (Dry Flood Prooﬁng Pre-arranged/Pre-located Group 1): Selective Dry Flood Prooﬁng with Customised Watertight Protection

This eighth group of temporary flood proofing includes Pre-arranged/Pre-located customised solutions, including temporary shields and watertight seals to prevent potential water seepage into the buildings—either one-piece or sectional, thus more innovative than wooden boards. Like the previous technique, its strategies only work on inner lines. However, it differs from the previous one because these measures are not deployed on the whole or most part of the perimeter of the exposed targets, but only on their weak points, which are likely to be accessed by water that gets inside the buildings: windows, doors, vents, etc. Solutions should be arranged for in advance so as to prepare devices to secure the barriers to the external surface of the buildings—the barriers belonging to this group do not adhere to each other, like in the previous group, nor do they mutually support themselves simply by leaning or being propped up and fixed against the constructing elements. The barriers (automatic and manual) must be then designed and configured in advance, long before any alarm that of a flood event would occur—i.e. during the preparatory period. Such techniques are suitable for strong, heavy buildings (masonry and concrete) whose external walls are waterproof and resistant to water action.

9.2.8.1 D.P.1.1—Flood Boards

This technique relies on individual operations to seal the main weak points in a building with respect to permeability and water submersion. Possible apertures include doors, windows, air ducts and vents, air-bricks, mailboxes, doorbells, cat-flap, etc. Such measures are undertaken only if all other construction components of a building have equal or similar water tightness properties. Their water tightness systems, such as those in charge of fixing gaskets or securing elements, generally are more sophisticated than the individual grooves in use with detachable flood gates (see section C.P.1.2). Working as the ultimate defence line, they must ensure a higher water tightness since any seeping water would enter a dry, inhabited environment—unlike for the protection of roads or neighbourhoods, which can tolerate it being ‘affected’ by water. Furthermore, such measures can be manufactured from flexible materials with no inner supporting properties, so they can be directly propped up and fixed against other surfaces. Doorways (and shop windows) are generally among the most vulnerable points of buildings, above all when these have no raised entrances—in such cases, though, there are often basement floors with equally vulnerable windows, window well or driveways. The first strategy consists in installing necessary watertight shields which are equipped with gaskets and capable of obtaining optimum side and lower adherence—not only by inserting them into purpose engineered grooves, but also through specific systems pressing the gaskets against the walls. Given some 9.2 Description of Temporary Flood Proofing Proposed Classes 203 exceptional scenarios where water levels are likely to be quite high, these boards can wholly span the openings. In such cases, the watertight fittings are not usually placed inside the perimeter of the openings, but outside their rims to better withstand the pressure, so they entail even more adequate and sophisticated operations of preliminary arrangement. The measures belonging to this group are generally installed on medium weight defence lines with rather low surface areas and very short deployment times. Small apparatus made principally of plastic or aluminium have been developed to solve the specific issues of some small building apertures such as air-conditioning ducts, vents installed because of gas ovens or wood fireplaces and so on, some of them include suitable grills to be fitted directly on vents. Table 9.8 shows a detailed schematisation of the abovementioned characteristics in comparison to the distinguishing factors that have been determined to choose among temporary flood proofing techniques. Figure 9.39 shows, in a simplified manner, a way to use this kind of technique (Figs. 9.40 and 9.41).

Fig. 9.39 Scheme of ﬂood board technique, front view (by way of an example—drawing not in scale) 204 9 Temporary Flood Prooﬁng Devices Analysis

Fig. 9.40 A selection of representative examples of ﬂood board technique 9.2 Description of Temporary Flood Prooﬁng Proposed Classes 205

Fig. 9.41 A couple of representative examples of ﬂood board technique, being potentially “dual use” in case of air pollution after industrial accident with clouds of toxic gases

9.2.8.2 D.P.1.2: Ground-Anchored Flood Gates/Barriers Protecting Building Entrances

Unlike the previous group, these modular solutions are suitable for almost any context, asking for no modifications to the buildings. They are secured and adhere to the ground—which usually consists of rigid or essentially smooth paving such as concrete or asphalt, or even covered surfaces—and they result in an arched or rectangular configuration in order to connect the waterproof walls that are located on both sides of the aperture being protected. Such solutions require no significant alteration (technical or aesthetical) to the building or to its doors/opening, since all ground fixing elements are placed in front of it. Once again, they can be used only if all other parts of the buildings have equal tightness properties. Table 9.8 shows a detailed schematisation of the abovementioned characteristics in comparison to the distinguishing factors that have been determined to help in the choice among temporary flood proofing techniques. Figure 9.42 shows a simplified scheme of use this kind of technique (Fig. 9.43). 206 9 Temporary Flood Proofing Devices Analysis

Fig. 9.42 Scheme of working mechanism of ground-anchored ﬂood gates, plan view (by way of an example—drawing not in scale)

Fig. 9.43 A couple of representative examples of ground-anchored ﬂood gates/barriers protecting building entrances technique 9.2 Description of Temporary Flood Prooﬁng Proposed Classes 207

Table 9.8 Flood boards and ground-anchored flood gates/barriers protecting building entrances: SENSO model evaluation factors SENSO model factors Dry Flood Proofing Pre-arranged/Pre-located D.P.1—Selective Solution group dry flood proofing with customised watertight protections Ground-anchored flood gates/ barriers protecting building Techniques Flood boards (D.P.1.1) entrances (D.P.1.2) Socio-economic context—(S) (S1) Available budget with regard to the area being protected—Costs 1. Procurement Medium Medium 2. Assembly/disassembly, Low Low transport and clearance operations 3. Maintenance/storage (when Medium Medium not in use) 4. Reusability (in more than in High High one flood event) 5. Alternative use Low (sometimes to protect in Low case of industrial accident with toxic gas clouds) (S2) Timely availability of trained workforce and/or possible self-employment for private individuals 1. Specific training courses are Yes—Medium Yes—Medium required 2. Technical (generic) skills at Yes—Medium Yes—Medium a professional level are required 3. Self-employment is possible Yes Yes for private individuals (only short line of defense) 4. Automatic solutions do not None None involve workforce—except for regular scheduled maintenance and surveillance (S3) Availability of auxiliary means of transport and equipment 1. Need for auxiliary equip- None None ment or specific means of transport Environment and event scenarios—(E) (E1) Performances in relation to water level h, flow velocity v and solid transport values—i.e. event scenarios Water level From moderate to high Moderate Flow velocity Moderate Low Solid transport and floating Low—sand or suspended soil, Low—sand or suspended materials branches and other light float- soil, branches and other light ing materials floating materials (continued) 208 9 Temporary Flood Proofing Devices Analysis

Table 9.8 (continued) SENSO model factors Dry Flood Proofing Pre-arranged/Pre-located D.P.1—Selective Solution group dry flood proofing with customised watertight protections Ground-anchored flood gates/ barriers protecting building Techniques Flood boards (D.P.1.1) entrances (D.P.1.2) (E2) Extension and type of Ideal for inner line Ideal for inner line span (or spans) being protected Suitable for short lengths Suitable for short lengths (E3) Need for preliminary Suitable for levelled and Suitable for levelled and studies and site preparation empty hard surfaces to be empty hard surfaces to be depending on ground selected or prepared selected or prepared morphology (E4) Building types, from The more suitable to be used The more suitable to be used foundations to construction set/propped against every kind set/propped against every materials and urbanization of buildings (wood or light kind of buildings (wood or context of constructions buildings included; crawlspace light buildings included; foundations excluded) crawlspace foundations excluded) The more suitable to be used set/propped against cultural heritage buildings Field operations—(O) (O1) Speed of installation and Time for the activation (made Time for the activation (made deployment by two workers with available by two workers with available equipment) of a 20 linear equipment) of a 20 linear meter barrier of a level of 1 m: meter barrier of a level of 1 m: <1h 1–3h (O2) Potential reuse and Light mobile apparatus, Light mobile apparatus, multipurpose use non-usable for different non-usable for different purposes purposes (O3) Preliminary territorial Apparatus requiring ‘light’ Apparatus requiring ‘light’ equipment and possible minor territorial equipment or build- territorial equipment or requirements for territorial ing arrangements building arrangements infrastructures (O4) Availability of materials Additional apparatus not Additional apparatus not and additional apparatus available in real time available in real time (O5) Removability and Apparatus inducing reduced Apparatus inducing reduced induced residual environmen- permanent changes to permanent changes to tal impact premises premises (O6) Quality and quantity of Removable apparatus requir- Removable apparatus requir- storage areas, when not in use ing safe storage against atmo- ing safe storage against spheric agents atmospheric agents (O7) Maintenance require- Apparatus non-reparable/non Apparatus non-reparable/non ments, operating times and replaceable on-site, requiring replaceable on-site, requiring potential repairs in case of frequent and regular frequent and regular damage, even when maintenance maintenance operational Usage variations None None 9.2 Description of Temporary Flood Proofing Proposed Classes 209

9.2.9 D.D.1 (Dry Flood Prooﬁng Demountable Group 1): Selective Dry Flood Prooﬁng with Demountable Watertight Protections

9.2.9.1 D.D.1.1: Flood Doors and Windows

This single-technique group represents a limit measure as it calls for important and firmly established modifications of buildings, though not as permanent barriers, but as predisposition to tightness. Anyway, when these barriers are shut, they are floodproof—therefore, such closure mechanisms must be thoroughly assessed prior to a flood event. These doors, windows or additional shields (comparable to insect screens for their use) can be opened either horizontally or vertically (drop-down) and result in on all four sides watertight closure mechanisms having compression seals on the whole perimeter, as well as thrusters to ensure the tightness of the seals. Both automatic and manual solutions should be arranged in advance. Mainly, these solutions stem from naval construction techniques. They can be used only if all other parts of the buildings have equal water tightness properties and in cases of particularly severe event scenarios. They can be additional to the usual doors or windows or openings of a building, or simply act by replacing their functions (in other words, the peculiarity of this group is to be barriers potentially much more shut than any other group, but not for flood protection reason, but for every day uses). Table 9.9 shows a detailed schematisation of the abovementioned characteristics in comparison to the distinguishing factors that have been determined to choose among temporary flood proofing techniques. Figure 9.44 shows a schematic illus- tration of this kind of technique (Fig. 9.45).

Fig. 9.44 Scheme of ﬂood doors and windows technique, front view (by way of an example—drawing not in scale) 210 9 Temporary Flood Prooﬁng Devices Analysis

Fig. 9.45 A selection of representative examples of ﬂood doors and windows technique 9.2 Description of Temporary Flood Prooﬁng Proposed Classes 211

Table 9.9 Flood doors and windows: SENSO model evaluation factors SENSO model factors Dry Flood Proofing Demountable D. D.1—Selective dry flood proofing with Solution group demountable watertight protections Techniques Flood doors and windows (D.D.1.1) Socio-economic context—(S) (S1) Available budget with regard to the area being protected—Costs 1. Procurement High 2. Assembly/disassembly, transport and clear- Low ance operations 3. Maintenance/storage (when not in use) Medium 4. Reusability (in more than in one flood event) High 5. Alternative use Low (biohazard protection and toxic gas clouds) (S2) Timely availability of trained workforce and/or possible self-employment for private individuals 1. Specific training courses are required None 2. Technical (generic) skills at a professional None level are required 3. Self-employment is possible for private Yes individuals (only short line of defense) 4. Automatic solutions do not involve work- Yes force—except for regular scheduled maintenance and surveillance (S3) Availability of auxiliary means of transport and equipment 1. Need for auxiliary equipment or specific None means of transport Environment and event scenarios—(E) (E1) Performances in relation to water level h, flow velocity v and solid transport values—i.e. event scenarios Water level High Flow velocity Moderate Solid transport and floating materials Sand or suspended soil, branches and other light floating materials (low) (E2) Extension and type of span (or spans) Ideal for inner lines being protected Suitable for short lengths (E3) Need for preliminary studies and site Suitable for levelled and empty hard surfaces preparation depending on ground morphology to be selected or prepared (E4) Building types, from foundations to con- The more suitable to be used set/propped struction materials and urbanization context of against every kind of buildings (wood or light constructions buildings included; crawlspace foundations excluded) Field operations—(O) (O1) Speed of installation and deployment Time for the activation (made by two workers with available equipment) of a 20 linear meter barrier of a level of 1 m: <1h (continued) 212 9 Temporary Flood Proofing Devices Analysis

Table 9.9 (continued) SENSO model factors Dry Flood Proofing Demountable D. D.1—Selective dry flood proofing with Solution group demountable watertight protections Techniques Flood doors and windows (D.D.1.1) (O2) Potential reuse and multipurpose use Non-mobile apparatus, non-usable for different purposes (O3) Preliminary territorial equipment and Apparatus requiring ‘light’ territorial equip- possible minor requirements for territorial ment or building arrangements infrastructures (O4) Availability of materials and additional Additional apparatus not available in real time apparatus (O5) Removability and induced residual envi- Apparatus inducing significant permanent ronmental impact changes to premises (O6) Quality and quantity of storage areas, Visible apparatus stored in (along) the defence when not in use line (O7) Maintenance requirements, operating Apparatus non-reparable/non replaceable times and potential repairs in case of damage, on-site, requiring frequent and regular even when operational maintenance Usage variations None

9.2.10 D.R.2 (Dry Flood Prooﬁng Removable Group 2): Complementary Dry Flood Prooﬁng of Buildings by Means of Removable Universal Apparatus

This group comprises two types of standardised or universal removable measures. Their use is complementary to many types of defence lines, both temporary and permanent, which belong to the ‘inner’ category. Their size is often small and their horizontal surface contact area is incredibly small. Once the procurement task is adequately accomplished, individual installation times on the building perimeter are usually short or very short.

9.2.10.1 D.R.2.1: Complementary Sealing Universal Apparatus

The solutions belonging to this group encompass a variety of individual devices that are purposely engineered to prevent floodwater from potentially entering buildings through common weak points, that is through the outer limit or perimeter walls (e.g. walls having air vents or gratings, etc.) or, conversely, through sewage disposal systems. This group includes self-adhesive rubber strips to cover air vents in walls or non-watertight gaps in window or door fixtures, watertight sewage stoppers for water basins (washbasins, bathtubs, showers, etc.), toilets or floor drains, drain 9.2 Description of Temporary Flood Proofing Proposed Classes 213 rigid covers or drain carpets (of the same type of those prescribed by ADR regulations; to be cautiously used to watertight outdoor manholes and sewers or ground ventilation grates; some of them are magnetic to adhere to the iron frame), and so on. Due to its characteristics, performances of this group of solutions related to water level, flow velocity and solid transport values are impossible to be estimated, because of the complementary role in defending from flood actions. Table 9.10 shows a detailed schematisation of the abovementioned characteristics in comparison with the distinguishing factors that have been determined to choose among temporary flood proofing techniques. Figure 9.46 shows some examples of this type of techniques (Fig. 9.47).

9.2.10.2 D.R.2.2: Smart Patching

The systems belonging to this group include solutions particularly apt to defend cultural heritage buildings, since these systems are purposely engineered, like the previous ones, to prevent ﬂoodwater from potentially entering buildings, but not through more or less common weak points of perimeter walls (e.g. walls having air vents or gratings, etc.) yet through windows and doors.

Fig. 9.46 Complementary sealing universal apparatus scheme, front view (by way of an example—drawing not in scale) 214 9 Temporary Flood Prooﬁng Devices Analysis

Fig. 9.47 A selection of representative examples of complementary dry ﬂood prooﬁng of buildings by means of removable universal apparatus technique

The basic idea of this technique is to have a kind of pliant and moldable device able to take the shape of the window or door perimeter and to counterbalance water pressure transferring the strengths to the building walls. This goal is, for instance, achievable using a soft inﬂatable and plastic material panel, exploiting the action of a little air compressor to seal perimeter, coupled with rigid bars, perpendicular to water pressure and resting to the perimetric wall, able to transfer water pressure and to give rigidity to the soft panel. 9.2 Description of Temporary Flood Prooﬁng Proposed Classes 215

Table 9.10 shows a detailed schematisation of the abovementioned characteristics in comparison with the distinguishing factors that have been determined to choose among temporary ﬂood prooﬁng techniques. Figure 9.48 shows some examples of this type of techniques (Fig. 9.49).

Fig. 9.48 Smart patching devices scheme ...front view (by way of an example—drawing not in scale)

Fig. 9.49 A couple of representative examples of smart patching technique 216 9 Temporary Flood Prooﬁng Devices Analysis

Table 9.10 Complementary sealing universal apparatus: SENSO model evaluation factors SENSO model factors Dry Flood Proofing Removable D.R.2—Complementary dry flood proofing of buildings through removable universal Solution category apparatus Complementary sealing Techniques universal apparatus (D.R.2.1) Smart patching (D.R.2.2) Socio-economic context—(S) (S1) Available budget with regard to the area being protected—Costs 1. Procurement Low Medium 2. Assembly/disassembly, Low Low transport and clearance operations 3. Maintenance/storage (when Low Low not in use) 4. Reusability (in more than in Medium High one flood event) 5. Alternative use Low (toxic gas clouds biohaz- Low (toxic gas clouds bio- ard protection) hazard protection) (S2) Timely availability of trained workforce and/or possible self-employment for private individuals 1. Specific training courses are None None required 2. Technical (generic) skills at None None a professional level are required 3. Self-employment is possi- Yes Yes ble for private individuals (only short line of defense) 4. Automatic solutions do not None None involve workforce—except for regular scheduled maintenance (S3) Availability of auxiliary means of transport and equipment 1. Need for auxiliary equip- None Yes, air compressor ment or specific means of transport Environment and event scenarios—(E) (E1) Performances in relation to water level h, flow velocity v and solid transport values—i.e. event scenarios Water level Not Applicable NA (comple- NA (complementary use) mentary use) Flow velocity NA (complementary use) Moderate Solid transport and floating NA (complementary use) Low materials (E2) Extension and type of Ideal for inner lines (comple- Ideal for inner lines (comple- span (or spans) being mentary use) mentary use) protected (continued) 9.2 Description of Temporary Flood Proofing Proposed Classes 217

Table 9.10 (continued) SENSO model factors Dry Flood Proofing Removable D.R.2—Complementary dry flood proofing of buildings through removable universal Solution category apparatus Complementary sealing Techniques universal apparatus (D.R.2.1) Smart patching (D.R.2.2) (E3) Need for preliminary None None studies and site preparation depending on ground morphology (E4) Building types, from The more suitable to be used The more suitable to be used foundations to construction set/propped against every kind set/propped against cultural materials and urbanization of buildings (wood or light heritage buildings context of constructions buildings included; crawlspace foundations excluded) Field operations—(O) (O1) Speed of installation and Time for the activation (made Time for the activation (made deployment by two workers with available by two workers with avail- equipment) of a 20 linear meter able equipment) of a 20 linear barrier of a level of 1 m: <1h meter barrier of a level of 1m:1–3h (O2) Potential reuse and Light mobile apparatus, Light mobile apparatus, multipurpose use non-usable for different non-usable for different purposes purposes (O3) Preliminary territorial Apparatus which does not need Apparatus which does not equipment and possible minor any territorial equipment need any territorial requirements for territorial equipment infrastructures (O4) Availability of materials Additional apparatus available Additional apparatus avail- and additional apparatus in real time from specialist able in real time from spe- suppliers cialist suppliers (O5) Removability and Light apparatus leaving no Light apparatus leaving no induced residual environmen- residuals (fully removable) residuals (fully removable) tal impact (O6) Quality and quantity of Removable apparatus requiring Removable apparatus requir- storage areas, when not in use safe storage against atmo- ing safe storage against spheric agents atmospheric agents (O7) Maintenance require- Apparatus non-reparable/non Apparatus non-reparable/non ments, operating times and replaceable on-site, requiring replaceable on-site, requiring potential repairs in case of frequent and regular frequent and regular damage, even when maintenance maintenance operational Usage variations None None 218 9 Temporary Flood Proofing Devices Analysis

9.2.11 C/D.1 (Floodwalls and Dry Flood Prooﬁng Temporary Complements Group 1): Mixed Solutions and Special Cases

This peculiar complementary group includes either cooperating—supporting one another—or collaborating solutions—working side by side, but also special measures that are not included in any of the previous groups. Thus, this last group of measures is a methodological note rather than a class. All different groups of temporary flood proofing techniques should not be considered as alternatives to each other, rather they can be mutually supportive or cooperate on different lines (in a multiple line configuration), depending on local scenarios and topologies. Two great examples are the use of sandbags as ‘finishing stage’ of other techniques, often securing some anchoring strips or connecting various defence elements, and the case of plastic sheets to protect barriers that are made of other materials. Not only does this case apply to defence lines that rely on different techniques, but also to those techniques that are used within a single defence line to convey or divert water flows into specific routes or sites—when it is not possible to convey them to permanent basins still having sufficient detention capacity—where other temporary techniques on a different defence line will be more effective and more likely to succeed in flood proofing. Often, a special case of “outdoor” good to be protected, using a solution complementary to those put in place on the identified defence lines, are vehicles, since vehicles are especially connected to the urban land, although they are fully mobile and consequently not always adequately defendable by the same barrier shielding a building. In order to protect those peculiar assets, some suppliers distribute large wrapping bags made of watertight plastic sheets. Once these are spread down on a parking ground, the vehicle can be parked, wrapped and sealed in the waterproof sheeting. Finally, it can be anchored to the ground by means of suitable harnesses to avoid floating and counterbalance buoyancy forces. Another similar special case is that of garbage containers and dumpsters. These typical, mobile objects standing in every area of many cities are often dangerous as they are subject to quickly receive enough hydrostatic pressure to float. If no permanent solutions have been found, as occurs with vehicles wrapped in bags, any possible fixing, anchoring and ballasting systems should be evaluated and set up by suitable operational teams—whose members could be those who also provide for their emptying—to prevent containers from floating around (e.g. using ropes or chains connected by hooks, spring-hooks or ballasts). Figure 9.50 illustrates schematically this kind of technique. Considering the peculiarity of this group, a detailed schematisation of its characteristics in comparison with the SENSO Model criteria is not needed (Fig. 9.51). 9.2 Description of Temporary Flood Proofing Proposed Classes 219

Fig. 9.50 Special techniques to defend cars or outdoor mobile ﬂoating goods. Front view (by way of an example—drawing not in scale)

Fig. 9.51 A couple of representative examples of car protection systems

9.2.12 E.R.1 (Wet Flood Prooﬁng Temporary Complements Group 1): Hydro-repellent Sacs or Similar Protections Systems for Indoor Movable Goods

This small complementary group includes another option, comparable to the one applied to vehicles, and follows to some extent the locally resilient approach of the wet flood proofing permanent defence strategy, that is the use of such type of bags (or similar solutions) to wrap (or to protect) domestic furniture such as tables, sofas and so on, which could not be moved away to security levels in time (flood protection bags). This kind of technique is based on the assumption that home structure and plants have been conceived or put in a situation of being permanently water resistant/water proof. Differently, it should be better to opt for another 220 9 Temporary Flood Proofing Devices Analysis

Fig. 9.52 Wet ﬂoodprooﬁng example scheme. Front view (by way of an example—drawing not in scale)

Fig. 9.53 A few representative examples of hydro-repellent sacs or similar protection systems for indoor movable goods technique

floodproofing techniques, able to protect the building as a whole. Figure 9.52 shows an example of using this type of techniques. In this case too, a detailed schematisation of its characteristics in comparison with the SENSO Model criteria is not needed (Fig. 9.53). 9.2 Description of Temporary Flood Proofing Proposed Classes 221

9.2.13 G.R.1 (Ground Lowering/Levelling of Free Land Temporary Complements Group 1): Water Diversion Temporary Activated Pipes or Bridges

The systems belonging to this complementary group are thought to prevent big amount or discharge of water to invade lower places and spaces (for instance: the excavations of foundations and underground services in building construction sites; passages or gardens below ground level used to reach basements (or spaces to be lived-in in the area around); underground entrances of rooms, garages, repositories or laboratories; depressed roads—especially in case of drainage system out of order or undersized). In this case, the strategy differs from the previous ones, because its aim is not to stop the mass of water, but it is always to transfer its ﬂux beyond the spaces to be defended. This solution is a good and economic alternative when the risk is a long-time stagnation of water in contact with the external surface of buildings (and obviously also in case of cultural heritage ones). These systems are engineerable as temporarily suspended pipes or eaves and often they need to be coupled with cooperating barriers to direct water to the pipe. This kind of technique, as the previous one, is based on the assumption that the area of the building or asset to be defended have been conceived or put in a situation of deﬁnitively convey the masses of water away. Differently, the application of this technique will result in a failure. Figure 9.54 shows an example of using this type of techniques. Once again, considering the different operation strategy of this complementary group, a detailed schematisation of its characteristics in comparison with the SENSO Model criteria is not needed.

Fig. 9.54 Water diversion temporary activated pipes scheme. Front view (by way of an example—drawing not in scale) 222 9 Temporary Flood Prooﬁng Devices Analysis

Fig. 9.55 A big scale example of water diversion temporary activated pipes technique (in this case applied to convey sewage waters)

Lastly, some more traditional ways to hold back ﬂoodings deserve to be expressly mentioned at this point, namely the potential supportive action by the already mentioned water pumps, or the functionality of creating raised paths, e.g. through boardwalks (better if anchored to the ground), wherever this can ensure human safety, especially when it comes to water ﬂow velocity (Fig. 9.55).

9.3 Emergency Flood Prooﬁng Techniques as ‘Transitional Solutions’ to Support Adaptation Policies Towards Urban Redevelopment and Building Restoration

The broad variety of temporary flood proofing solutions described in this chapter is presented by organising and construing its complexity with the purpose of making it more usable in respect of its not enough exploited applications in practice (Alfieri et al. 2016). In doing so, we hope we have illustrated almost all different contexts and circumstances in which they can come in handy. At the same time, we acknowledge that many countries, both European and non-European, shall experience long transitional periods before they can achieve some consolidated territorial assets according to permanent and acceptable flood risk References 223 safety levels. This is related, for instance, to the slow-paced development of structural defence programmes (assuming the hypothesis that they are feasible and effective); building relocation, land-use changes and demolition plans, when possible, need too much time to be implemented; it takes too long for buildings which need to be abandoned or undergo a radical flood proofing restoration before they complete their life cycle. Within this framework, in order to protect assets, properties, historical and cultural heritage and, above all, human beings, it becomes increasingly reasonable to sustain specific policies which may foster suitable adaptation solutions to the flood risk conditions of extremely or ill-advisedly urbanised lands (Bichard and Kazmierczak 2012), or even whole regions of the world, as some coastal areas typically are, which are more exposed than others to the effects of climate change (Bignami and Biagi 2018). On the basis of territorial risk analyses, resulting from the cross-examination of flood hazard and land-use (and any related future purposes), it is possible to determine some priority operation levels beginning with specific surveys investigating vulnerabilities and exposed values data of buildings to be defended. Therefore, some needed variations of long-term territorial assets can be considered by making use of the transitory defence performances that are offered by flood proofing techniques, especially temporary ones and small permanent ones, which can therefore be regarded as useful transitional short-term or ‘bridge’ solutions. As concerns town planners and building operators, working for decision makers, who deal with flood risk reduction policies, this approach could help tackle the multidisciplinary issues of urban land redevelopment and building restoration, such as difficult operation of planning with regard to the procurement of sufficient production factors (investment capitals and/or alternative real estate assets).

References

Alfieri L, Feyen L, Di Baldassarre G (2016) Increasing flood risk under climate change: a pan-European assessment of the benefits of four adaptation strategies. Clim Change 136:507–521. https://doi.org/ 10.1007/s10584-016-1641-1 Bichard E, Kazmierczak A (2012) Are homeowners willing to adapt to and mitigate the effects of climate change? Clim Change 112:633–654. https://doi.org/10.1007/s10584-011-0257-8 Bignami DF (2010) Protezione civile e riduzione del rischio disastri. Maggioli, Sant’Arcangelo di Romagna Bignami DF, Biagi E (2018) Flood resilient districts: integrating expert and community knowledge in Genoa. In: Smart, resilient and transition cities – emerging approaches and tools for a climate- sensitive urban development, 1st Edition. ISBN: 9780128114773, Elsevier, pp. 257–265, 320 pp Chou J, Wu J (2014) Success factors of enhanced disaster resilience in urban community. Nat Hazards 74:661–686 224 9 Temporary Flood Proofing Devices Analysis

Websites https://trapbag.com/ https://www.screwfix.com/p/gravitas-hydrosnake-expanding-water-barrier-2-pack/6687d https://sgiindustries.com/product-category/flood-prevention-and-spillage-control/inflatable-flood- barrier/ https://www.lindstrandtech.com/?portfolio¼automatic-inflatable-flood-barrier https://www.fluvial-innovations.co.uk/0-5m-high-flood-stop-barrier/ https://www.floodblockbarrier.com/ http://www.gumotex-rescue-systems.com/flood-control-barriers-with-steel-structure http://www.floodcontrolinternational.com.au/PRODUCTS/FLOOD-BARRIERS/flood-barriers.php https://www.floodsax.us.com/ http://www.metallbau-koeln-whm.de/en/Flood-protection/Flood-protection.html http://www.svitap.co.uk/anti-flood-barriers/ https://www.em-solutions.it/ http://noaq.com/en/home/ http://www.inero.se/en/home.htm http://www.cpm-group.com/products/water-management/flood-protection-blocks/modular-floodwalls/ http://floodbreak.com/projects/garage-solutions/ https://www.flashflooddoors.co.uk/ http://www.aquadam.net/ http://www.floodcontrolinternational.com/index.php https://www.floodark.com/barrier/ http://aquobex.com/ http://www.whitehouseconstruction.co.uk/ https://dutchdam.com/ https://www.psfloodbarriers.com/product/mechanical-room-flood-door-single/ https://njmeishuo.en.made-in-china.com/product/LNdmUCcjlTkv/China-Extruded-Aluminum- Flood-Barrier-for-Garage-Doors.html https://www.ibsengineeredproducts.co.uk/disaster-prevention/general-flood-protection/ https://floodcontrol.asia/ http://www.flood-products.co.uk/smart-air-bricks-p-43332.html#.WzQx9_ZuJ2s https://stopflood.it/ https://www.floodpanel.com/flood-protection-products/flood-panel-post-flood-barrier-system/ https://thefloodcompany.co.uk/products/hydroshield-flood-barrier/ http://www.drain-tech.com/drain-flood-protector/ http://donatz.info/floor-drain-trap-guard/floor-drain-trap-guard-interesting-on-intended-for-green- drain-inline-4-liquidbreaker-16/ http://landshutters.com/flood-bags http://schrodinglandscape.com/landscaping-services/grading-excavation/ https://smartvent.com/professionals/category/architects https://ddc-resiliencedatabase.wikispaces.com/Wet+Floodproofing http://www.floodsafeusa.com/gallery/flood-walls/ http://www.stcplanning.org/usr/Program_Areas/Flood_Mitigation/Floodproofing/FProof_04_ Dry_Floodproof.pdf http://rsaprotect.com/floodcontrol/worlds-first-patented-flood-control-panel/ Chapter 10 Tests, Guidelines and Norms

10.1 Overview

This chapter presents an overview of tests, guidelines and norms about flood proofing devices and measures, coming from several different Countries. As a general framework, the focus of this chapter is first on “single building defence” (which can also be identified as “inner line of defence”) measures, and then on “areal defence” measures (which can be implemented at different scales, case by case), according to the classification already described in Chap. 9. Anyway, such an overview is not expected to be exhaustive, updated and fully detailed, but it is aimed at providing a summary of general criteria remarking on similarities and differences as well as operational methods and the related difficulties (especially) in terms of achievable accuracy in representing real field situations. Moreover, it must be pointed out that significant differences, in terms of performances, may occur sometimes when floodproofing devices are running in real applications instead of laboratory tests. Nevertheless, those differences can be quite limited if the personnel in charge of storing, mounting and demounting those devices is well trained and follow the proper procedures to manage them.

10.2 Single Building Defence (Inner Line of Defence) 10.2.1 USA Approaches

10.2.1.1 US Army Corps of Engineers/FEMA

In the USA, federal, state and local agencies have researched techniques, promoted flood proofing as a viable flood protection measure, also assisting property owners and implementing their own projects. Some Federal agencies, notably the U.S. Army Corps of Engineers (USACE) and the Department of Homeland Security’s Federal

Emergency Management Agency (FEMA), have financed flood proofing projects. Some States have even implemented public information and financial assistance programs (USACE 2000, 2005). Most regulations for flood proofing are based on the minimum standards of the National Flood Insurance Program (NFIP). The NFIP sets minimum regulatory standards for constructing, modifying, or repairing buildings located in the floodplain to keep flood losses to a minimum. Over 19,000 flood-prone communities have adopted and enforced the minimum standards and many have more restrictive requirements. The NFIP limits some flood proofing; it prohibits obstructions, such as berms and floodwalls, in floodways. However, enclosing the area under an elevated building is not allowed in coastal high hazard areas. The NFIP also requires structure specific flood proofing for a building not in the floodway that is substantially improved or substantially damaged. “Substantially damaged” is defined as “damage of any origin sustained by a structure whereby the cost of restoring the structure to its before damaged condition would equal or exceed 50% of the market value of the structure before the damage occurred”. Houses that have been substantially damaged or are being substantially improved (renovated) must be elevated to or above the 100-year flood level. Non-residential buildings must be elevated or dry flood proofed. Many States and Communities have more restrictive standards than the NFIP. The most common is freeboard, requiring an extra margin of safety in the design and construction of flood protection measures to account for waves, debris, hydraulic surge, or lack of flooding data. Some prohibit buildings or residences in certain areas, such as a floodplain or conservation zone. In these Communities, substantially damaged buildings would not be allowed to be rebuilt unless they are relocated. Indeed, raising or moving a structure so that floodwaters cannot reach damageable portions of it is an effective flood proofing approach (USACE 2000). The recommended floodproofing techniques are those already described in Chap. 7: elevation, relocation, barriers, dry and wet floodproofing.

10.2.1.2 Laboratory Tests

High flood damage costs to property have produced an awareness that nonstructural methods should be developed to augment flood protection provided by dams, levees, and similar structures. Because of the frequency and extent of flooding, strong initiatives to protect buildings from repetitive flood damage losses will provide a quick return on investment. The structural integrity of a building must be known or the building may be flood proofed to an extent that it will be excessively stressed and damaged or collapsed. It was determined by United States Army Corps of Engineers (USACE 1988)by model and prototype tests that brick-veneer and concrete-block walls can withstand only approximately 3 feet (about 1 m) of static waterhead without damage. If a building or home is loaded to excessive depths, it can fail instantaneously and possibly result in injury or death to occupants. 10.2 Single Building Defence (Inner Line of Defence) 227

Closures, materials, and systems were tested to determine the effectiveness in protecting homes or buildings from floodwaters. The following conclusions were derived from the tests. • A watertight closure must have gasket material at its connection to the sidewalls and bottom and must be bolted. The connections for the closure at the sidewalls and floor must be continuous and sealed securely to the walls and the floor. • Water will flow freely through a brick wall and along the space at any water barrier between thicknesses of brick. • Two layers of brick will allow a brick wall to support greater water depths. • A brick or concrete-block wall can be protected against water flowing through it excessively by using a thick coating. This type of coating must be applied with great care or the wall will not be leakproof. • Clear liquid coatings, even when low head pressures are present, will not stop water from penetrating a brick-veneer or concrete-block wall. • Epoxy, polyurethane, and asphalt coatings were not dependable in keeping water from penetrating a brick-veneer or concrete-block wall. • Some cementitious coatings will stop the penetration of water (under head pressure) through a brick-veneer or concrete-block wall, but many of these coatings are not durable. Two coatings were tested which were durable and did stop the penetration of water through a brick wall. Coatings which can be painted on are less expensive to apply and are as effective as any troweled-on coating. • Systems tests demonstrated that a simple continuous system is the most reliable, with snap connections being less reliable. A simple system which is adequate to protect a building from floodwaters.

10.2.1.3 Norms for Non-residential Buildings

The federal United States National Flood Insurance Program (NFIP), regarding the design of non-residential buildings, requires that they must be flood proofing in their Base Flood Elevation (BFE) and that the insurance contracts must include the prescription for a given basic level of safety (USACE 2005). In particular, a building is classified as a flood proofing one if the building is 1 foot above the possible level of the maximum inundation depth (but 2 feet if the maximum inundation level is uncertain). Moreover, any floodproofing project must be certified according to the following criteria: a non residential building must be sealed below the Base Flood Elevation (BFE), and a qualified engineer must analyse and/or review the structural design, the specifications, the construction design and methods, and the registration of the certification must include the specific level above the sea for which the building becomes flood proofed. 228 10 Tests, Guidelines and Norms

10.2.1.4 Underground Parkings

Underground parking are of great interest because the inundation of such closed buildings can cause relevant damage to the building above and to the devices thereby positioned, like mechanical and electrical devices, ventilation, lightening, lifts and pumps. Therefore, a dry ﬂood prooﬁng approach must always be adopted in case of underground parkings, taking into account the loads against the building structures due to hydrostatic and hydrodynamic forces caused by an inundation. Moreover, the loads on the upper part of the structure are usually transferred to the underground parkings below, and so a structural failure of the underground parkings can cause the collapse of the whole building.

10.2.1.5 The University of Alabama Tests for Residential Buildings

In June 2004, the University of Alabama published the results of an interesting experimental research about the effects of inundations on residential buildings (University of Alabama 2004). The primary purpose of the project was to identify materials and methods that will make the envelope of a house flood damage resistant. Flood damage resistant materials and systems are intended to be used to repair houses subsequent to flooding. This project was also intended to develop methods of restoring the envelopes of houses that have been flooded but are repairable and may be subject to future flooding. Then if the house floods again, damage will not be as extensive as in previous flood events and restoration costs and efforts will be minimized. The purpose of the first pair of field tests was to establish a baseline for typical current residential construction practice. The first test modules used materials and systems that were commonly found in residential envelopes throughout the U.S. The purpose of the second pair of field tests was to begin evaluating potential residential envelope materials and systems that were projected to be more flood- damage resistant and restorable than the conventional materials and systems tested in the first pair of tests. The purpose of testing the third slab-on-grade module was to attempt to dry flood proof the module (no floodwater within the structure). If the module could be sealed well enough to prevent water from entering, then this would be an effective method of making the interior materials and systems flood damage resistant. The third crawl space module was tested in the same manner as the previous modules and provided an opportunity to do flood tests of additional residential materials and systems. Another purpose of the project was to develop the methodology to collect representative, measured, reproducible (i.e. scientific) data on how various residential materials and systems respond to flooding conditions so that future recommendations 10.2 Single Building Defence (Inner Line of Defence) 229 for repairing flood damaged houses could be based on scientific data. An additional benefit of collecting this data is that it will be used in the development of a standard test procedure which could lead to the certification of building materials and systems as flood damage resistant.

10.2.2 Australian Guidelines

The Australian State of New South Wales issued an interesting document regarding construction and securing of buildings in areas exposed to ﬂooding hazards (Hawkesbury-Nepean Floodplain Management Steering Committee 2006). Such a document considers three main aspects of damaging: • The water impact against the components of the building, • The degradation of the materials due to the contact with water, • The movement of the foundations due to land subsidence.

10.2.2.1 Damages Due to Water Impact

The damages due to water impact against a building are related essentially to: • External walls: the external walls of any building are the first to be hit by a flooding impact; the whole action of the water directly impacts against them, and this generates different situations: – Disruption in different points, – Wall arching, – Complete breakdown of the wall and of its coating, both outside and inside the building. Those damages due to water impact against a building are related essentially to: 1. Hydrostatic pressure, which increases as water depth increases; 2. Hydrodynamic forces of water in movement, together with hydrostatic pressure; 3. Impact of debris flow. Usually, the external walls of a building begin to deteriorate and can even collapse when the water level reaches about 1 m. A building hit by a flooding undergoes different kinds of hydrostatic forces (Fig. 10.1): • Side loads: they act in horizontal, vertical or inclined directions: so they tend to move the building laterally and to tip it; • Vertical loads: they act vertically downward on horizontal or inclined surfaces and also on elements like pavements and roofs; they are caused by the weight of the water and the imbibition of the materials; 230 10 Tests, Guidelines and Norms

Flood level

Slab floor Ground level

Upward Buoyancy force Basement floor

Hydrostatic pressure acts on walls and concrete slab floors. Pressure on basement walls and the slab is higher due to the extra depth and Additional Upward the weight of saturated soils. pressure from Buoyancy saturated soil force

Fig. 10.1 Hydrostatic forces (Hawkesbury-Nepean Floodplain Management Steering Committee 2006)

STUD FRAME CONSTRUCTION modes of failure due to lateral (i.e flood) load

Ties support brick cladding and transfer lateral load to the frame All of the following can lead to severe cracking, FLOOD movement or FORCE collapse of the brick cladding

Excessive deflection of frame Brick ties breaking, buckling or pulling out Stud frame failure in bending, or the top or bottom sliding

Research was also carried out to analyse loading and failure mechanisms in masonry brick wall construction to understand the forces that brick can withstand from moving waters.

Fig. 10.2 Reaction of a brick wall (Hawkesbury-Nepean Floodplain Management Steering Committee 2006)

• Buoyancy forces: they act vertically upward on horizontal or inclined surfaces like attic, pavements and foundations; the impossibility of balancing these forces can move the house away from the ground, making it float (especially in case of buildings built with light materials). The perimetral walls of a building are the first hit by stream flow impact. So they must resist to the hydrostatic forces keeping the structure unbroken, especially in case of dry-floodproofing, which creates heavier actions and stresses. Figure 10.2 shows the different reactions of a brick wall hit by a streamflow; an experimental study carried out by US Army Corps of Engineers has pointed out that 10.2 Single Building Defence (Inner Line of Defence) 231

Fig. 10.3 Damages due to hydrostatic forces (Hawkesbury-Nepean Floodplain Management Steering Committee 2006) a brick wall is able to sustain the pressure rates due to a water depth of about 75 cm and 1 m, before the structure collapses as shown by Fig. 10.3. In all the areas subject to a flood risk with a water depth which could easily reach 1 m, the wet-floodproofing approach that allows to balance the hydrostatic pressure between outside and inside the building, to prevent its collapse, must be adopted (Fig. 10.4). In particular, Fig. 10.5 shows the wet-floodproofing scheme that must be followed to save the structural integrity by balancing the hydrostatic forces. The same concept is remarked on the Canadian document: “Floodproofing Protect your home against flooding”, with the following key features of a flood aware designed house suited in both high and low hazard areas. 1. Construct external walls on upper stories with fibreboard for ease of repair after flooding. 232 10 Tests, Guidelines and Norms

Flood level

Slab on ground floor Ground level

Below ground basement floor

Upward Buoyancy force

Hydrostatic pressures are Higher upward buoyancy force balanced when water is Additional allowed to enter the house. pressure from saturated soil

Fig. 10.4 Balance of the hydrostatic forces in wet-ﬂoodprooﬁng approach (Hawkesbury-Nepean Floodplain Management Steering Committee 2006)

2. Waterproof bracing e.g. steel strap or waterproof plywood. 3. Consider use of steel sheet roofing to reduce repair costs. 4. Use flood compatible floor beams with flooring such as waterproof plywood. 5. Use flood compatible wall plate connectors and brick ties to strengthen structure. 6. Elevate electricity box. 7. Protect and anchor tanks. 8. Use non-absorbent insulation such as polystyrene panels. 9. Design foundations such as slab on ground against erosion and differential settlement. 10. Design and construct wall cavity to ensure adequate ventilation and access for cleaning. 11. Construct external ground floor walls in double brick or masonry for strength and ease of repair. 12. Allow water entry and exit via vents and flaps to balance internal and external water pressures. All of these features allow the use of wet-floodproofing with success, minimizing damage and consequently also the cost of restoration.

10.2.2.2 Damages Due to Solid Transport Impact

Of particular interest and significance is the design of buildings that are able to resist the impact of debris; In the case of floods, the flow is able to transport debris of any kind and size, from water bottles to trees to cars. Debris hitting a house can cause a lot of damage and, added to hydrostatic pressure, can cause the structure to collapse. For this reason, the US approach has been to design houses that can withstand three different levels of impact from debris: 10.2 Single Building Defence (Inner Line of Defence) 233

Fig. 10.5 Wet-floodproofing design in a floodable area (Hawkesbury-Nepean Floodplain Man- agement Steering Committee 2006)

• Normal impact loads: The house has to be able to withstand the impact with of a mass of 1000 pounds traveling at the velocity of the ﬂow, concentrated in a square foot. • Special impact loads: The house has to be able to withstand a constant load of 100 pounds per foot (148.9 kg/m) acting horizontally for more than one foot of width. • Extreme impact loads: It is impossible to design buildings to withstand the impact of other buildings collapsing on the top of them. 234 10 Tests, Guidelines and Norms

To protect a building from a flood, the choice of building materials is of great importance. For this reason, in the document guide different materials can be used in different areas of the home, evaluating the pros and cons of each. The analysis and the careful assessment of the methods and materials of the construction allow the builder to obtain, upon completion and after evaluation of a specialized external technician, a certificate of suitability for the building in case of flooding. This certification method is also very common in the United States, where the interventions made on a home allows it to face an extraordinary flood event which are examined by specialized external technicians issuing a so-called “certificate” attesting to ‘Suitability of the interventions’ carried out.

10.2.3 European Guidelines

In May 2007, a guide document issued by a consortium managed by CIRIA: “Improving the flood performance of new buildings. Flood resilient construction” was issued in London, this is a thorough analysis of the flood problem in the United Kingdom (CIRIA DEFRA 2007). The paper proposes a series of actions to be taken to improve the response of buildings during an extraordinary flood event; in particular, it is written in order to: • Provide easy and practical guidance for new buildings located in low-risk areas in order to reduce flood damage. • Provide recommendations on the construction of flood-proof buildings. • Do not facilitate and promote the construction of buildings in high flood risk areas. The guidelines provided in this document are derived from laboratory tests specially designed to evaluate the behaviour of different materials and the usual building techniques in flood conditions. It is important to note that the guide does not cover the following design aspects: 1. Structural damages caused by flow velocity or impact with debris. 2. Effects due to aging of materials. 3. Costs of the different building materials. 4. Impact of variation in environmental conditions (frost-thaw). 5. Effect of flood water contamination. 6. Easy cleaning of materials and finishes. 7. Moisture-induced growths (mold). 8. Flooding from internal sources (tank-boilers burst). 9. Problems caused by insufficient roof drainage. 10. Modern construction methods. 11. In-depth examination of the fixtures. To better analyze the interventions to be made on buildings to make them able to cope with flooding, the guide analyzes what happens in case of flooding. 10.2 Single Building Defence (Inner Line of Defence) 235

Fig. 10.6 Potential routes for entry of ﬂood water into a dwelling (CIRIA and EA 2003)

Water can easily penetrate into a house because existing building regulations do not require the use of materials that can withstand a prolonged submersion, water can penetrate through (Fig. 10.6): • Bricks and concrete blocks. • Partition walls of terraced buildings. • Expansion joints between walls made of different materials. • Hollow bricks. • Door thresholds. • Inadequate sealing of doors and windows. • Cracks in the outer walls. • Construction wall failures. 236 10 Tests, Guidelines and Norms

Table 10.1 Damages in case of an extraordinary flood event Water depth Damages to the building Damages to services and accessories Below ground floor Possible erosion under foun- Damage to power sockets and other level dations causing instability services in basements and cellars Absorption of excessive Damage to accessories in basements moisture and cellars Floor breaking down because of excessive pressure Possible metal corrosion Mold appearance Half a meter above Water and mud infiltration into Damage to water and gas gases ground level the wall cavities Damage to boilers and low heating Possibility that the pavement systems severs and tends to float Need of replacing furniture and uphol- Damage to interior finishes stery such as wall coverings Need of replacing piping insulation Floors can tend to swell Wooden materials will probably have to be replaced Damage to internal and external doors Mold appearance Corrosion of metal parts Over half a meter Increase wall damage Damage to higher units, electrical above ground level Possible structural damage services and home appliances above 0.6 m of water Possible impact damage with large debris Ground erosion due to the stream

• Interface cracks between different materials. • Services (telephone cables, ventilation conducts, toilets). • Subsoil and basement infiltration. Damages caused by flooding are uncountable, in addition to possible structural damage to the house, the greatest risk to the health and safety of occupants located inside the building. When flood waters are contaminated, the risk for the inhabitants is greater because they lack the essential goods such as drinking water, often the effects of a flood will continue after the end of the event. Table 10.1 shows the most frequent damage to buildings in case of an extraordinary event. Since damages caused by a flood may be of various kinds, there is no common building design regulation for a full range of buildings. This guide offers several design options, the choice of which varies depending on the type of flood expected in a particular area and available space. The following factors should be considered before planning: 10.2 Single Building Defence (Inner Line of Defence) 237

Table 10.2 Interventions according to the water depth in ﬂood conditions Water depth Approach Mitigation measures Above To allow water to enter the building to avoid Design the drainage of ﬂooded 0.6 m structural damage due to hydrostatic pressure water Use low permeability materials up to 0.3 m Design access to all spaces to facilitate drying and cleaning Use materials resistant to water contact Between Try to prevent access to water; if structural Use low permeability materials 0.3 and problems arise then approach as above up to 0.3 m 0.6 m Design access to all spaces to facilitate drying and cleaning Use materials resistant to water contact Below To prevent access to water Use low-permeability building 0.3 m materials Designing raised thresholds

• Potential sources of flooding: marine water can cause corrosion due to high salinity especially during prolonged periods, river water and streams can cause structural damage due to current velocity. • Flood level expected: full flood level for different occurrence frequencies or return periods. • Duration: generally, inundations due to large rivers or groundwater rises have a long duration (days or weeks); so, a prolonged contact with water can lead to structural damage. • Frequency: in areas where floods are frequent and modest, the best approach is the dry-floodproofing system that allows waterproofing of the house by preventing water from entering, thus reducing damage. Where water levels do not allow this method to be used, wet-floodproofing must be used; in this case, using water-resistant building materials and low restoration costs is of fundamental importance. • Depth: the key parameter is the water level estimate as it allows people to select one of the following two strategies: – Dry-floodproofing, preventing water from entering the building; – Wet-floodproofing, allowing water entry.

In order to decide on the most appropriate method to be used, the ﬂood level must be appraised (Table 10.2): • Below 0.3 m; • Between 0.3 m and 0.6 m; • Above 0.6 m. 238 10 Tests, Guidelines and Norms

Fig. 10.7 Example of data collected on building materials: variation of seepage rate with time (CIRIA DEFRA 2007)

Fig. 10.8 Example of effect of render on leakage rate through brick wall (CIRIA DEFRA 2007)

10.2.3.1 Laboratory Test

Numerous laboratory tests have been carried out on building materials and compos- ites (walls and ﬂoors) to verify their behaviour under ﬂood conditions (Figs. 10.7, 10.8 and 10.9). 10.2 Single Building Defence (Inner Line of Defence) 239

Fig. 10.9 Example of effect of render on surface drying of external brick wall (reduction in surface moisture; 1.0 equivalent to pre-ﬂood condition) (CIRIA DEFRA 2007)

So, a large number of data on infiltration and water leakage has been collected over time. In particular, the leakage of individual materials is referred to as “infiltration”, while the term “loss” is used for walls made up of several materials. The tests were carried out trying to accurately simulate a real situation, even if sediment transport, debris impact, and the speed of the current were not taken into account in the test. The walls were subject to a water depth of 1 m for 4 days, 3 days only externally and all the 4 days internally, simulating the water entering the house, then the walls were allowed to dry naturally for a period of 6 days. The behaviour between different walls has come out to be quite varied, in terms of loss a typical brick walls and water-level concrete with a height of 1 m loses up to 400 l/h (or 360 l/h/m of wall). It has been found that the rate of loss tends to decrease considerably over time but, if maintained, a hypothetical room of 3 m Â 3 m would reach a water level within it of 0.2 m in just 5 h (assuming water penetrates only through the wall). Using specifically designed brickwork and waterproofing, the wall loss rate is only 0.02 m of water within a room of the same size after 5 h. Of course, given the variety of building materials available in the market, the test is limited to those most commonly used. 240 10 Tests, Guidelines and Norms

10.2.3.2 SMARTeST

Another major European document in this field is represented by the “Flood Resilience Technologies” issued by the “SMARTeST Project” Commission in May 2013 (SMARTeST 2013). It aims to provide a guide and a method for testing the reactions of different buildings after a flood; in fact, despite numerous technologies to contain a flood such as mobile barriers, there is a risk that water may enter the dwelling, so building buildings that can withstand an extraordinary event are to be considered fundamental. This guide does not cover the waterproofing of buildings subject to hydrostatic and hydrodynamic water pressures and does not provide a method for estimating the damage caused by a flood event. There is a need for a premise on the approach to be used: depending on the situation, water can easily penetrate a building in a number of preferential routes, so there are two different approaches, which are—as already seen—respectively wet floodproofing and dry floodproofing. This document provides guidance on how to use one or the other technique: • Up to 300 mm height of water is possible to use dry floodproofing. • From 300 to 600 mm dry floodproofing is applicable to most buildings, but for structurally weaker buildings it is possible to use a combination of the two methods. • From 600 to 900 mm, wet floodproofing is required, dry floodproofing can be used to exclude water until the building is able to withstand the pressure. • Above 900 mm it is imperative to think of wet floodproofing as the only alternative. Once the best approach to be used have been chosen, it is necessary to test the buildings reaction to any flooding to verify that the materials used allow minimizing the damages while preserving the integrity of the house. In particular, the document provides a number of considerations and guidance on the procedure to be used to correctly carry out laboratory tests on the walls and floors of a building.

10.3 Areal Defence 10.3.1 FM Approval Standard

FM Global, Inc. is a global insurance company that certiﬁes commercial facilities and disaster prevention products. This standard describes the requirements of FM Approvals for ﬂood protection systems, river use, or conditions related to a full event (ANSI FM 2013). 10.3 Areal Defence 241

10.3.1.1 Tests About Materials and Components

The components and the materials of a flood barrier are tested in accordance with this standard model. However, not all tests within this section are applicable to the various product types. Additionally, if a component cannot be adequately tested through the tests specified in the standard, it may be necessary to perform further specific tests. Performance tests can be conducted for a single component, on the various components assembled or with the entire barrier system. Material tests may be considered unnecessary at the discretion of FM Approvals if a preliminary test has been performed by a National Research and Testing Laboratory (NRTL) certified by the Department of Science, Technology and Medicine (OSHA). The documentation must be presented to demonstrate that they comply with the requirements and confirm that these tests have been carried out as described in the ASTM standards and performed with ISO 17025 certified devices.

10.3.1.2 Tests About Temporary Perimetral Barriers

The performance test of temporary perimeter barriers has been designed to simulate river flood conditions. All of the tests in this section replicate events that may occur during a single flood. Consequently, all the tests must be completed in sequence with the same product (Table 10.3). Performance verification must be carried out at the US Army Corps of Engineers, ERDC Coastal and Hydraulics Laboratory located in Vickisburg, Mississippi (USACE 2007). Figures 10.10 and 10.11 describe the layout and the impact scheme or the barriers. Large and small repairs to a perimeter barrier in any part of the test are only allowed at the discretion of FM Approvals. Important repairs may require a new check of the entire set of test and/or additional tests. Up to three small repairs are granted, but adjustments may be made to the project, installation, use and maintenance of the barrier.

10.3.1.3 Tests About Barriers for Building Openings

The performance test concerning barriers for building openings have been designed to simulate quasi-static river ﬂood conditions, that is a slow increase in water level with minimum wavelengths and the impact of beveled debris. Tests must be performed in sequence, as shown by Table 10.4, with the same sample. The tests are carried out within a structure capable of retaining the maximum water level for the barrier for at least 22 h. The size of the test structure must meet the requirements for each test. 242 10 Tests, Guidelines and Norms

Table 10.3 Tests for temporary perimeter barriers (USACE 2007)

Description of Water conditions the test Deptha Other conditions Duration Installation –– According to manufacturer specifications Hydrostatic 1 ft (~0.30 m) – 22 h load 2 ft (~0.61 m) – 22 h 100% Â h – 22 h Hydrodynamic 66.7% Â h Low waves 2 Ä 3in 7h load (~51 Ä 76 mm) 66.7% Â h Medium waves 6 Ä 8in 10 min (3 times) (~152 Ä 203 mm) 66.7% Â h High waves 10 Ä 12 in 10 min (~245 Ä 305 mm) 80% Â h Low waves 2 Ä 3in 1 h (min) (~51 Ä 76 mm) 7 h (max) 80% Â h Medium waves 6 Ä 8in 10 min (3 times) (~152 Ä 203 mm) 80% Â h High waves 10 Ä 12 in (~ 10 min 245Ä305 mm) Overflow 1 in (~25 mm) – 1h of overflow Impact with 66.7% Â h Trunk diameter 12 in – debris (~30 cm) Weight 610 lb (~277 kg) at 7 ft/s (~2.13 m/s) 66.7% Â h Trunk diameter 17 in (~43 – cm) Weight 790 lb (~358 kg) at 7 ft/s (~2.13 m/s) In flow 66.7% Â h Flow velocity 7 ft/s 1h (~2.13 m/s) Final hydro- 100% Â h N/A 1 h (min) static load 22 h (max) aThe maximum depth is specified by the manufacturer for the barrier, and defined as “h”

Additional impacts on the product or on the frame can be included in the documentation as deemed necessary by FM Approvals (like hinges, plastic parts, etc.). The impact on the barrier must be such that the edge of the impacting object hits the predetermined position on the product (Fig. 10.12). The impact test against the barrier is performed by lifting the object to a height of 4 ft (~1.22 m) above the impact point. Then it is dropped in such a way that it undergoes gravitational acceleration, through a circular trajectory, and impacts the barrier horizontally. The impact force E (600 J), calculated as potential energy, is determined by the length of the trajectory and the weight of the impacting object: 10.3 Areal Defence 243

Fig. 10.10 Layout and construction of the barrier (ANSI FM 2013)

E ¼ m Á g Á h where m is the mass of the impacting object (110 lb or 50 kg), g is the gravity acceleration (32.2 ft/s2 or 9.81 m/s2), and h is the height from which the impacting thing falls (4 ft or 1.22 m). After each impact it must be measured the permanent deformation and check that any dents at the impact point do not compromise the barrier functionality. The deformation is measured by the original position of the barrier along its base.

10.3.2 SMARTeST Project, Flood Resilience Technologies

The SMARTeST project has been funded by a European Union research program covering the area’s technologies for increased security during ﬂood events (SMARTeST 2013). The project has been co-ordinated by the United Kingdom’s Building Research Establishment and it involved 10 European research institutes. It has also been supported by various national groups for international dissemination and implementation. The results obtained are intended to outline the functions that an anti-ﬂood barrier must meet, indicating the necessary parameters and variables, and should be considered a guidelines when testing one of these types of products. 244 10 Tests, Guidelines and Norms

Fig. 10.11 Impact test scheme (ANSI FM 2013)

10.3.2.1 Standards and Protocols

Table 10.5 presents the existing protocols and national standards that are related to laboratory tests for anti-flooding, perimeter and aperture barriers. FM Global is a global industrial and insurance company that certifies commercial structures and flood prevention products. British Standards Institution (BSI) is the UK’s national regulatory body and produces standards on a wide range of products, services and processes. 10.3 Areal Defence 245

Table 10.4 Tests about barriers for building openings Test description Conditions Duration Mounting – According to manufacturer specifications Hydrostatic load 100% of h Æ 0.25 in (~0.6 cm) 22 h Reassembly Disassembly and reassembly According to manufacturer specifications Dynamic load Impact on the weakest point of the barrier – impact Hydrostatic load 100% of h Æ 0.25 in (~0.6 cm) 1 h Reassembly Disassembly and reassembly According to manufacturer specifications Dynamic load Impact against the barrier, with a support – impact structure Hydrostatic load 100% of h Æ 0.25 in (~0.6 cm) 1 h

Fig. 10.12 Impact test scheme (ANSI FM 2013) 246 10 Tests, Guidelines and Norms

Table 10.5 Existing reference documents for product testing Existing document Type Category Organization Approval 2510 Other protocol document Building aperture tech- FM Global nology Perimeter technology PAS 1188-1 National speciﬁcations, available to Building aperture tech- BSI PAS 1188-2 the public nology PAS 1188-3 Perimeter technology PAS 1188-4 CSTB Other protocol document Building aperture CSTB protocol technology DIN 19569-4 National norms Building aperture tech- DIN nology Perimeter technology

Center for Science and Technique du Bâtiment (CSTB) is the French national organization providing research, innovation, consulting, experimentation, training and certifying services for construction in France. CSTB is a member of EOTA and is an approval body nominated by ETA (European Technical Agreement). The French Department of Infrastructure requested a Protocol in 2004 to provide guidance on barriers for openings, in order to allow users a better understanding of the performance of available products. DIN 19569 is the German norm for wastewater treatment plants and describes the principles for the design of structures and technical equipment. It is published by Deutsches Institut für Normung (the German Institute for Standardization—DIN). It also defines structural and technical design of specific equipment that are relevant to flood protection products.

Contents of the Documents

With regard to the construction of open technology, the FM Global Protocol, PAS 1188-1 and the CSTB Protocol have many points in common. There are similarities between FM Global Protocol, PAS 1188-2 and PAS 1188-4 for perimeter technologies. The main observations on these reference documents are as follows: • Hydrostatic tests: – Sequential ﬁll: the rate, or steps, of the depth of the water level described in the tests is varied and this may affect the products differently; permanent products can work differently than temporary barriers. – The duration of the test is between 22 and 48 h, this difference in the parameter may be signiﬁcant in the case of sliding. 10.3 Areal Defence 247

– The surface of the support for the opening technologies must be brickwork for PAS 1188-1, Concrete for FM Global Protocol and Cement or Steel for the CSTB protocol. – The acceptable loss rate is: For perimeter barriers: 40 l/h/m according to PAS 1188 and 45 l/h/m according to FM Global Protocol. For opening barriers: 1 l/h/m in both documents. • Hydrodynamic load tests: – According to PAS 1188, it is not necessary to perform tests to verify the effect of incident waves. – Induced wave test characteristics and flow-related tests may differ slightly between PAS 1188 and FM Global Protocol. – An overflow test is required only by the FM Global Protocol. – For technologies about barriers for openings: waves and flows are considered by PAS 1188-1 but not by FM Global Protocol and CSTB. • Safety is evaluated by flexion tests in CSTB protocol while it is indirectly determined by deformation tests according to FM Global Protocol and according to PAS 1188. • Resilience tests are not specified in PAS 1188. In the DIN 19569-4 norm the waterproofing classes are defined by reference to the dispersion rates (Table 10.6). The measurement conditions differ from other test protocols but are relevant to perimeter and opening barriers. The test procedure is described as follows: • The measurement of the dispersion frequency refers to the water line, which is defined as the contact surface of the seal between the frame and the plate. • The water pressure condition must be agreed between the manufacturer and the control subject. • Tests must be carried out with distilled water. • The measurement time is 10 min. The CSTB protocol limits the maximum height of the barriers for building openings at 0.9 m (existing buildings are not designed to withstand a hydraulic load of more than one meter of water and not to create difficulties for rescue teams).

Table 10.6 Waterproof classes according to DIN 19569-4 Class Maximum permissible leakage rates per meter of the water line (l/s/m) 1 Between 0.3 and 1.0 2 Between 0.1 and 0.3 3 Between 0.05 and 0.1 4 Between 0.02 and 0.05 5 Less than 0.02 248 10 Tests, Guidelines and Norms