Environmental Engineering and Management Journal October 2020, Vol. 19, No. 10, 1835-1846 http://www.eemj.icpm.tuiasi.ro/; http://www.eemj.eu

“Gheorghe Asachi” Technical University of Iasi, Romania

NATURE-BASED SOLUTIONS FOR FLOOD MANAGEMENT: A STUDY CONDUCTED IN LABARO - DISTRICT, ,

Giulia Pandolfi1, Jessica Pettinari2

1Architecture Department - Urban studies, University of Roma Tre, Largo Giovanni Battista Marzi, N10 – 00154, Roma 2Architecture Department - Landscape, University of Rome Sapienza, Piazza Borghese, N9 - 00186 Roma

Abstract

‘Labaro-Prima Porta’ is a district in the outskirts of Rome, increasingly afflicted by recurrent floods. In order to reduce the local runoff volume, this paper defines a resilience and twofold strategy. At first, the use of a hydrologic software, called Storm Water Management Model (SWMM), along the research makes possible the evaluation of which Nature-based Solutions (NbS) are more effective in terms of runoff management. The results demonstrate short-term positive effects, with an immediate reduction of the local discharge of about 8%. The second phase of the study explores the possibility of designing a resilient ‘Labaro-Prima Porta’ district. A master plan, structured in two overlapping scales, is proposed. One large-scale, improving the ecological network of the Veio Park and the rivers close to the urban settlements; in the second layer a green blue infrastructure at the district scale is defined, including a 3.3 km greenway as an urban and ecological corridor. The overall objective of this study is to provide theoretical support for the “sponge city” theory.

Key words: hydro-ecological infrastructure, landscape design, SWMM, nature-based solutions, sponge city, urban water management

Received: February, 2020; Revised final: June, 2020; Accepted: July, 2020; Published in final edited form: October, 2020

1. Introduction landscape structure, besides not considering the social aspects at all. On the contrary, this work highlights the The growing flood risk is a major challenge importance of working following environmentally today for land and urban planning: there has never sustainable lines joining together the simulation with been a stronger incentive to re-think our approach to SMWW of the urban runoff (Rossman, 2010) and the environment and to use differently land, water and importance of urban and landscape design. The design space in our towns and cities. One of the urbanization of city roads should be adjusted timely, since it is a direct effects is the continuous growth of the very important part of urban development. It would be impervious areas, which interferes with the natural crucial to create ecological grass ditches, sunken lawn flow of the water cycle, and increases the urban runoff. areas, rain gardens and permeable pavement. Zhang et In recent years, many storm events have haunted the al. (2009) used SWMM to simulate the surface runoff cities, where in most cases the urban sewerage is no of a residential area in Nanjing which was longer correctly dimensioned due to recent extreme reconstructed with sunken lawn areas and permeable rain events. The tendency in water management of the pavement (Zhen-ci and Yuongchen, 2017) studied the current policies is to favor fast and expensive solutions relationship between rainfall and runoff in the area when the damage is already done. Italian authorities, under four different underlying surfaces conditions, in particular, have often shown little interest in where, thanks to the distributed water stability model, environmental issues, harming the territorial and the work achieves some possible suggestions to how

 Author to whom all correspondence should be addressed: e-mail: [email protected]

Pandolfi and Pettinari/Environmental Engineering and Management Journal 19 (2020), 10, 1835-1846 to contribute scientific to the creation of an ecological each other to solve problems from different scales and city. Other studies analyzed the effect of different maximize environmental, economic, and social kinds of Nature-based Solutions (NbS) on the control benefits” (Liang and Hou, 2018). of surface runoff, such as the beneficial hydraulic The paper focuses on Labaro-Prima Porta effects of green roofs (Bliss et al., 2009; Gregoire and District, located in the north of Rome, as a case study Clausen, 2011; Lamera et al., 2014), rainwater storage area to assess other content to be added to Sponge City tanks (Abbott et al., 2007) and draining parking lots theory. In particular, regarding the four points (Collins et al., 2008). mentioned above, particular attention was given to In these latter 10 years the most interesting point 1, 2 and 4. research steps that kept together modeling approach, case study and landscape where carried out on chinese 2. Case study territory since the Chinese government launched the sponge city pilot construction in 2015. There is a long The study focuses on Labaro-Prima Porta, a list of case study investigated, but here we mention: district in the outskirts of Rome (Italy), increasingly Beijing, Liupanshui and Qunli National Wetland Park afflicted by recurrent floods, even if the drainage in Harbin, which define how rain-runoff control system has been recently improved (Fig.1). The effects and landscape security pattern are essential for negative impacts of rainwater in Labaro-Prima Porta sponge city theory construction (Kongjian et al., 2015; is the result of different aspects: 1) the neighborhood Xia et al. 2017). A more recent paper describes four was built during the first decades of the second aspects that a sponge city construction must have: 1) postwar period, mostly out of planning, without taking should consider and be in line with local conditions; into account adequate urbanization criteria, not only 2) in order to play a better role it should take into from an environmental point of view, but even from a account the concept of an ecological city and a smart urban one; 2) greater waterproofing of soils due to city; 3) should requires the active participation of asphalt and other similar materials does not allow the more citizens; 4) “… requires intensive natural water cycle; 3) recent effects of climate change interdisciplinary cooperation and cross-scale magnified these structural problems in Rome (Filpa research. Due to the complexity of the construction of and Ombuen, 2014) specially in some neighborhoods sponge cities, multidisciplinary cooperation is like Labaro-Prima Porta (Benelli and Camerata, required. The multi-professionals are integrated with 2014).

Fig. 1. Labaro-Prima Porta, simulation of the flooded areas on the event 31 January 2014

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To this end, the study describes a twofold network transport layer, built with SWMM, is strategy where, thanks to the use of an open-source collected from the Department of Hydraulic hydrologic software, called SWMM it is possible to Engineering of Roma Tre University, since the start an analysis about which devices, depending on Department in 2005 started working on the the amount of water stored, have greater effectiveness identification of the causes of flooding in Labaro- in the context of the project. The research explores Prima Porta district, in collaboration with Rome three different operational steps and investigates also Municipality and the Civil Protection Agency, for a possible master plan design. The study is divided which the adaptation works to the system were then into two chapters and final results. made starting from 2015 until 2018. Finally, the The first chapter describes how the ‘Urban analysis regarding the main statistics of the Hydrologic Model’ was built. In order to study the distribution of channel lengths and hill-slope for the potential of SWMM and to elaborate a new ‘Urban transport layer were carried out by (Volpi et al., 2012), Hydrologic Model’ stackable with the existing Sewer and the urban drainage system replies the method used Model created by the Department of Hydraulic for Warangal Campus (Rangari et al., 2018), but in Engineering of Roma Tre University (Calenda and general is the procedure suggested in SWMM manual Mancini, 2009; Calenda et al., 2009; DE, 2005; (Gironas et al., 2010). DSIMU, 2015), it was necessary to improve the detail on the ‘Land Area Layer’, defining more accurately: urban density, property status, type of coverage (flat or pitched) and soil permeability. To this end it was necessary to use different mapping software DEM, GIS and CAD (Jiang et al., 2010) that could provide the geometric and quantitative characteristics in a form compatible (layers) with the previous Sewer Model. The second chapter shows a possible design application on the local context. The project intends to exploit the critical aspects as a potential, utilizing the hydro-morphology of the terrain to create a sustainable water drainage system, in order to slow down the water descent into the hilly area. The project is articulated in two different strategies: 1) improvement of the ecological network of the adjoining Veio’s park to increase the urban resilience

2) create a connected green and blue infrastructure in the urban settlement. Fig. 2. Simplification of SWMM layers Finally, ‘Results and discussion’ consists in the evaluation on the ‘Urban Hydrologic Model’, at first Basically, SWMM works as shown in the on public buildings and then on private ones too, of previous figure (Fig. 2) and it consist in 4 main layer: urban runoff reduction (about 8%). Basically, it a) Atmospheric layer, where the rain events are focuses on the positive effects of NbS, quantitatively inserted, divided mainly into two types: single event evaluating them through the constant application of with a duration of a few hours or continuous event, SWMM and specifically green roofs, draining parking respectively days or months. In this study a lots and water tanks, which have immediate effects rectangular single event of about 1 hr was chosen; b) (Qing-yun et al., 2014). These are known Land area, the territory is divided into sub-basins, interventions that are finding increasing application, which receive the waters from the Atmospheric Layer although they are not always accompanied by and the surface runoff from the other portions of the quantitative assessments on an urban and territorial territory. The analysis of this work focuses primarily scale. on the small-scale identification of Land Area Layer, since the study is conducted by architects; C) 2.1. Data and urban hydrologic model Groundwater Layer, defines the water infiltrated into the ground where absorption times depend on the type Data of the current study is obtained from of soil; d) Transport layer, is the sewage network and different agencies: the Digital Elevation Model map – it is composed by junctions, conduits, channels, DEM (elevation of 5 m in this model) is produced by manholes, etc. forming a graph consisting of links and th European Environment Agency (EEA, 2015); nodes. As mentioned above this is the starting point rainfall data regarding the last 20 years was procured issued by the Department of Hydraulic Engineering on from ISPRA (Higher Institute for the Environmental which the work in question overlaps. Protection and Research and Conte et al., 2015), while For a more detailed analysis, a smaller subarea data for recent rainfall events was taken from Castel of 64.5 acres was chosen on the Nord side of the Giubileo weather station. Moreover, the drainage district, in order to study the storm water management

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Pandolfi and Pettinari/Environmental Engineering and Management Journal 19 (2020), 10, 1835-1846 as an example of the neighborhood (Fig. 3). This area with water since they are classified as alluvial soil was chosen because: 1) it has a separated sewage (light blu in Fig. 4). Since in this case the soil is system ending at the point defined as Outfall, 2) the already at its full capacity of water-absorption, the transport layer was made by the Department of sub-catchments that captain in these areas are treated Hydraulic Engineering of Roma Tre University and 3) as if they had 95% impervious. Differently, all other being a hilly and heavily urbanized area features that Sub-catchments will have 5% as initial parameter of acts as a demonstration example of the whole area. To imperviousness and then in the remaining 95% apply the methods described below, the project site features of each type of soil is introduced as follows must first be divided into sub-watersheds areas, that (DRCG, 1969): are defined based on topography (water lines, roads, - Horton coefficients: The parameters for this property etc.) and drainage patterns (manholes, drains model include, a) Maximum infiltration rate is the systems, pipe union etc.). initial infiltration rate at the start of a storm; b) These watershed areas require physiographic Minimum infiltration rate is the limiting infiltration information such as configuration of the channel rate that the soil attains when fully saturated. The latter network, location of drainage systems, channel length has a wide range of values depending on soil type from and slope, and sub catchment geometric properties. 3 cm/hr for clays up to 12 cm/hr for sand; c) Decay The drainage networks consist of about 137 nodes and coefficient: this parameter determines how quickly the one final Outfall, situated at the end of the study area infiltration rate “decays” from the initial maximum (South-East). All the sub-catchments dividing lines value down to the minimum value. Typical values are based on the ‘Land area collection’, they are range between 2 to 7 hr-1. plotted along roads, streets, and territorial elements. - Roughness coefficient, has separate values for the Finally, the sub-catchments are linked to the nearby impervious and pervious areas of a sub-catchment, for manholes according to the topography and to the example 0.6 for dense wooded areas versus 0.012 for sewer network. Fig. 3 reflects the structure of the smooth asphalt. drainage system and the sub-catchment delineation - Depression Storage (Engman, 1986) this results. Each sub-catchment was classified in different parameter is divided in two sections: the ‘Impervious parameters following the map shown in Fig. 4 and Area’ that is usually around 0.3 mm and the ‘Pervious Table 1, which include: Area’ from 0.3 mm - 10 mm, depending on the amount of present vegetation. For example, the deep wood 1. Infiltration parameters determines the maximum parameter (10 mm), and all - In order to simulate the correct imperviousness and of this is directly added in the software. Depression infiltration in the context area it was necessary to storage represents all the elements and areas that could understand what kind of soil and substrate have surface ponding, such as the water that can be characterizes this sector. As shown in Fig. 4 there are collected by flat roofs and vegetation, and surface some sub-catchments that are completely saturated wetting.

Fig. 3. Sewage system of the Nord-Est part of Labaro-Prima Porta

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Fig. 4. Geological map. Study of the type of soil in the study area

In the study case the empirical values are 3. Geometrical and territorial parameters specifically, for Clay Areas: Horton coefficients: There are some other parameters imputed within Maximum infiltration rate: 75 mm/h, Minimum the software, Table 1 shows and example of it, such as: infiltration rate: 3 mm/h, Decay Constant: 2 h-1 , Name, is the name of each Sub-catchment used in the Roughness coefficient: Impervious Area: 0.024 mm, SWMM Software; Outlet, is the sewer ending point, Pervious Area: 0.4 mm. Depression Storage: positioned at the lowest altimetrically spot; Area is the Impervious Area: 0.3 mm, Pervious Area: 6 mm. Tuff total area, expressed in acres; Width, can be defined as Areas: Horton coefficients: Maximum infiltration rate: the sub-catchment’s subdivisions, obtained by the 125 mm/h, Minimum infiltration rate: 6.50 mm/h, length of the longest overland flow path that water can Decay Constant: 4 h-1 ; Roughness coefficient: travel; Slope, is the average slope within the Sub- Impervious Area: 0.024 mm, Pervious Area: 0.6 mm; catchment. Depression Storage: Impervious Area: 0.3 mm, Total district of the east side of Labaro-Prima Pervious Area: 8 mm Porta has a total surface of 64,5 acres, where, based on the described parameters, the percentage average is 2. Surface cover parameters 49.2 % impermeable and 50.6% permeable, Surface is mainly divided in land-use respectively 317,330 sq m and 326,267 sq m. This classes of permeability as you can see in the following percentage is anomalous for the urban context of Rome, figure (Fig. 5). Semi-permeable surface was evaluated that usually has a higher percentage of impervious from the subtraction from the total area of impermeable areas. and permeable surface, the result split up in equal parts But in this case, we are working on a to impermeable and permeable. In this study the neighborhood being on the edge of the city in close amount of impervious areas was established by contact with countryside and with some nearby natural delimiting the following areas in each watershed: systems, like River and the Veio’s Park, so these streets, parking lots, buildings divided in flat roof or parameters reflect this urban context. These surface pitched roof and ½ of Semi-permeable. These areas are data and all the other layer’s data are introduced into estimate with just a 25% of Depression Storage, being the software for the simulation. The graph shown in mainly asphalted or characterized by construction Fig. 6 is made at the end node (J59 node) of the sewage materials. Unless special circumstances are known to system, just before the final Outfall. In the Urban exist, a percent imperviousness area without depression Model the outflow observed a volume (CMS - cubic storage of 25% is recommended. Lastly, permeable meters per second) of the total flow equal to 3.94 surface is defined as: woods, grass and ½ of Semi- cms/hr. permeable.

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Fig. 5. Example of the investigation process of permeability that was made for each sub-catchment

Table 1. Example of input parameters for each sub-catchment

NAME TOT IMPER. PERME. FLAT PITCH. PARK STREET WOOD GRASS SEMI-PERME.

MQ MQ % MQ % MQ MQ MQ MQ MQ MQ MQ

FR1-1 14,865 6,696 45 8,169 55 122 1,627 1,252 1850 4,175 2,150 3,688

2.2. Labaro-Prima Porta’s landscape design

The project intends to exploit the critical aspects of flooding and urban runoff, as a potential, utilizing the hydro-morphology of the terrain to create a system of floodable micro-parks and drainage systems, in order to slow down the water descent into the hilly areas. Territorial and landscape interventions will resume connections from the city to the open spaces, on the whole, the project significantly changes the profile of the district. The design takes in consideration the urban space afflicted by recurrent floods, between the rivers system (Tiber river, Prima Porta’s and Cremera’s ditches) and Veio’s park, an important green ecological corridor where natural beauty blends perfectly with local history and culture. In order to define an intervention strategy the whole neighborhood was divided into types of flooding, such as: pluvial flooding, due to heavy rainfall and Fig. 6. Graph of the Urban developed runoff, the total flow malfunction of the sewer system; river flooding, along volume is 3.94 (CMS/hr). Y-axis describes the surface the valleys of main rivers and groundwater flooding runoff in cubic meters per second, while the X-axis caused by intense rainfall and/or by the rising of the describes the amount of time of the event, in this case is around 1 hr hydrometric level of the local stream network, which, in turn, determine a rising of the water table, not Having developed this integrated model, it was compensated by draining pumps. For the development possible to proceed with the analysis of the margins of of the sustainable water drainage system two different action within which to propose possible interventions scales of approach are established: aimed at reducing and reusing surface water, 1) The territorial scale intervention aims to otherwise destined to the sewage network. In restores the connectivity of urban settlement with the particular, they were outlined three NbS: 1) green natural local system, where the realization of a system roofs, whose beneficial hydraulic effects are now of floodable river-parks can concurrently slow down consolidated nationally and internationally; 2) the water and re-enforce the local ecosystem. The rainwater storage tanks and 3) draining parking lots. rapid expansion of impervious urban surfaces and the Finally, the introduced devices are divided into construction of major road infrastructure has different scenarios according to the degree of local destroyed the ecological networks, therefore is private support to the project. important to establish physical, visual and ecological

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Nature-based solutions for flood management: A study conducted in Labaro - Prima Porta District, Rome, Italy connectivity between built-up areas of the city and the rain garden, bioswales, permeable pavements, surrounding natural areas. The action performed are: wetlands, green and blue roofs. In particular, increase biodiversity with the elimination of alien bioswales are highly recommended for their species (Robinia pseudoacacia and Ailanthus functionality, in terms of quantity of water intercepted altissima); promote urban foresty, planting native and runoff management PURVIS (2018). Usually, in riparian vegetation (Populus spp., Salix spp.); use an the urban context stormwater runs off roofs, sidewalks enviromental engineering approach with partial and roads and it takes many pollutants directly into elimination of weeds (comunity of Arundo donax, gutters and storm drains, otherwise with the Phragmites australis, Rubus ulmifolius) for the safety application of multiple bioswales (DEPOGI, 2017) of waterways and realize new linear corridors that pass water flow is diverted into them where, with the use of through the agricoltural system, with mixed tree-lined native plants, different benefits are made (Fig. 8). In (Ulmus minor, Quercus pubescens, Quercus cerris, particular, urban runoff slows down, new habitat for Acer campestre, Morus alba) and mixed border wildlife is created and water is purified through these hedges (Crataegus monogyna, Spartium junceum, processes: phytovolatilization in which plants uptake Pyracantha coccinea, Rosa canica, Rosa contaminants and release them into the atmosphere as sempervirens) wich also provides shelter and food for they transpire, the phyto-stabilization with the animals. sequestration of contaminants in the soil through 2) The urban scale main objective is to intercept absorption or accumulation around the root zone, the the largest amount of rainwater in order to reduce phytodegradation a metabolic process that breaks runoff and flooding and to restore the natural down or degrades contaminants into simpler hydrological cycle. For this purpose, a green and blue molecules or elements. Finally, detained water also water management infrastructure was designed in the filters through the soil helping to recharge the district, (DEP, 2012) improving the connection and groundwater. the multifunctionality of new urban spaces, with Through this linear system developed on the further benefits: economic (increase economic value), greenway, water was collected, phyto-purified and environmental (more biodiversity, decrease of infiltrated into the soil for a total of 3.30 Km and 1655 impermeable surface) and social (more welfare, public sq meters of capturing surface, partially restoring awareness, education on sustainability issues). The water natural cycle. Taking into consideration an area multi-stage realization of a main Greenway and of 2000 sq meters of the greenway, permeable surfaces secondary Greenstreet as a linear system in the center are 1440 sq meters of total area, against 560 sq meters of the district solves the neighborhood water drainage of impermeable surface, with an increment of 80% system. (Fig. 7) Specifically the devices applied are: (Fig. 9).

Fig. 7. Urban scale master-plan. The Greenway system connects the main parks and areas of the neighborhood as an ecological and urban connection corridor

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Fig. 8. Bioswales detail. Phyto-depuration plant and system operation for the collection of rainwater

Fig. 9. Section of permeable surface before and after the project and comparison of the difference in permeability. In this case with the project there is an 80% increase of permeable surface.

Also, in this case planting is promoted. The can be a risk in the urban settlement. Differently, the existing boulevards are mostly made by Pinus pinea new species proposed in the project Acer campestre and Cupressus sempervirens, species widely used in and Acer monspessulanum are characterized by being Rome for their iconography and also for their fast native species with small size and less problematic growth. In particular, Pinus pinea is not a roots system. recommended plant to be used on streets, mainly for Finally, the Greenway, in addition to two reasons: 1) his big roots have the tendency to performing the function of water collector, constitutes branch out the surface cracking the asphalt; 2) the the center of an urban reactivation, where open spaces alteration of the growth condition due to urban soil are an incentive for urban regeneration and social compaction, elevated pH, altered temperature and integration. Different devices have been hypothesized: moisture patterns and the presence of contaminants, for pedestrian some sustainable modal-split travel is

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Nature-based solutions for flood management: A study conducted in Labaro - Prima Porta District, Rome, Italy designed; for bicycle repairer different paths are to evaluate their effectiveness, whether taken defined, creating a new circuit that joins the existing individually or combined with each other, with the one along Tiber river; for school children it’s possible possibility of identifying the fewest number of to walk in safety through the Greenway, which interventions with the maximum effectiveness in connects schools, libraries, sports centers, markets and terms of costs/benefits. This operation also includes a parks. recognition of the territory and what the context can make available in terms of open spaces for landscape 3. Results and discussion design. Final result in terms of quantity of water stored with Nature-base Solution are defined in the area The study here presented shows a possible represented in Fig. 10, but it could be interesting to guideline for the realization of a sponge city in the impute also the urban design in SWMM and quantify Italian territory, which can be defined by a set of the beneficial effects it exercises. actions: 1) Analysis of natural conditions, which differ 3.1. Nature-based solutions from one territory to another. In particular it is important to review the local conditions in terms of In the Urban developed model, the outflow climate (change) and flood vulnerability. The observed a volume (CMS - cubic meters per second) reference study for this section is Filpa and Ombuen, of the total flow equal to 3.94 cms/hr. The graph in 2014; Fig. 11 shows how the sum of the three NbS (80% 2) The use of stormwater models such as, private - 100% public) produce a decrease of the rain ILLUDAS, MIKE-SWMM, MIKE-URBAN, peak equal to 8.6% of the total, respectively of 3.60 MOUSE, SWMM, STORM, TRRL and UCURM cms/hr. This result is composed of draining parking which could develop a map of the hydrogeological lots, of which a single 100% adhesion scenario is context with identification of the flows of the existing envisaged for a 70% draining surface (Table 2). In the sewage system (hydraulic basins, underground project area there are 13,998 sq meters of parking lots, channels, plant drains, etc.). In this case, the work of which about 10,000 are transformed into draining regarding the sewage model was made by the areas. The impact on the rainwater cycle was assessed Department of Hydraulic Engineering of Roma Tre based on the final flow rate at the last pipeline Node University, but a good method to follow for SWMM J59 (m3/second). In particular, the flood waves is made by Rangari et al. (2018); estimated for the return time RT = 10 years and rain 3) Identification of the devices, depending on the durations d = 1 hour with the combination of the urban section under examination, is suitable for Nature-based Solutions, are shown associated together solving the water problem (green roofs, tanks, in Fig. 11 and in different combination in Fig. 12. draining parking lots, etc.). Nature-base Solution used

Fig. 10. Public and private areas

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Fig. 11. NbS associated together vs Urban developed. Y-axis describes the surface runoff in cubic meters per second, while the X-axis describes the amount of time of the event, in this case is about 1 hr

Table 2. Results Green roofs vs. Water tanks

Green roofs Transformed Private Small buildings M buildings Big buildings areas SCENARIO N Transformed N Transformed N Transformed surface surface surface 75 % HIGH 54 3.884 m2 79 11.493 8 4.530 19.906 m2 Public Small buildings M buildings Big buildings Transformed Areas SCENARIO N Transformed N Transformed N Transformed surface surface surface 75 % ALL 25 1.887 m2 67 12. 943 9 7.109 21.939 m2 TOT 41.846 m2 = 6.5% of tot. area Water tanks Small buildings M buildings Big buildings Private (flat and pitched) (pitched) (pitched) Total 1 tank per building 2 tanks per building at least 3 tanks per building SCENARIO N Cubic m N Cubic m N Cubic m N Cubic m stored stored stored stored HIGH 60 240 116 928 10 184 360 1.241 Public Small Buildings M buildings Big buildings Total Flat roof 2 tanks per building 4 tanks per building At least 3 tanks SCENARIO N Cubic m N Cubic m N Cubic m N Cubic m stored stored stored stored ALL 25 100 67 536 9 270 101 906 Public Small Buildings M buildings Big buildings Pitched Total 2 tanks per building 4 tanks per building At least 3 tanks Roof SCENARIO N Cubic m N Cubic m N Cubic m N Cubic m stored stored stored stored ALL 15 60 45 360 5 150 65 570 TOT 2,670

Fig. 12. First graphic: combination of Draining parking lots and Green roofs - reduction of surface runoff to 3.63 cubic meters per second / hr (- 7.9%); Second graphic: combination of Draining parking and Water tanks - reduction of surface runoff to 3.75 cubic meters per second / hr (- 4.9%); Third graphic: combination of Green roofs and Water tanks- reduction of surface runoff to 3.68 cubic meters per second / hr (- 6.8%).

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Analyzing the temporal development of the 4. Conclusions flood waves of the curves associated with the three different scenarios, we can distinguish the effects of Flooded squares and streets, urban forests, the interventions in: urban devices, wet parks, increase of absorbent 1) you can quantify the amount of water stored surfaces, etc. these are just some of the elements that depending on which device is used, but the storage could merge into a new image of an ecological and interventions could reduce but not eliminate urban sponge city. The need is to trace a general rethinking flood (engineering-oriented approach); on how a sponge city should appear, in terms of design 2) it is interesting to observe how it is not of the relationship between landscape, environment certain that the total sum of the interventions and social systems, where ecology can become hypothesized is actually the best solution in terms of creativity and where water, redetermining its founding management and reduction of the surface runoff and nature, can become a first useful agent for a new urban in terms of economic and social costs/benefits. As design. Usability gradually promote new values and shown in Fig. 11 and Fig. 12 carrying out the protective behaviors, of which, going back from the interweaving of all the interventions together does not citizen to the top decision-making, landscape always reach a satisfactory increasing value. As seen architecture aspires to make everyone aware of what in the figures shown, the curve varies slightly, we pass world we could live in. by the decrease of 8.6% in the case of the sum of the Practical solutions for water flood adaptation three interventions to a decrease of 7.9% with the must be combined with a unitary design of the urban match of Draining parking lots (P) and Green roofs space, which takes into account the territorial and (T.V.). Therefore, we can establish that in this case landscape context, but also the local urban structure. study the best combination of intervention, in terms of In order for the adaptation strategy to work on all amount of water held and costs/benefits, is the defined elements, this dual nature should be kept combination of P and T.V. In particular, is together: a unitary project through the definition of newsworthy that the percentages of the decrease in aesthetic characteristics relevant to the old and new outflow for individual interventions should not be landscape and the necessary contemporary emergency added together because the final effect is not equal to techniques. the sum, but is a different effect linked to the Therefore, the overall objective of this study is associations of interventions and the reference to provide theoretical support for the “sponge city” context. Although in this final evaluation (point 2) the theory, where the general benefits can be listed as best cost / benefit ratio is taken into consideration, it is follows: • reduction of surface runoff • improved water necessary to emphasize the importance of starting to quality • preservation of urban biodiversity • promote the collection (water tanks) and the phyto- mitigation of climate change • reduction of air depuration of rainwater in our territory. In Rome, for pollution • stimulation of green economy • example, there is no law prohibiting the use of preservation of the natural and cultural heritage • drinking water to water private or public gardens, stimulation of social innovation • improvement of small plots or large plots. It is therefore necessary to environmental quality • landscape design. point out that drinking water resources are drastically decreasing and that increasingly difficult times are References ahead in terms of the amount of drinking water available for everyone. Furthermore, as we have Abbott S., Caughley B., Douwes J., (2007), The recently seen, long periods of drought are much more Microbiological Quality of Roof-Collected Rainwater of Private Dwellings in New Zealand, In: Rainwater and frequent in our country, which risk ruining local crops Urban Design, Barton A.C.T. (Ed.), 13th Int. 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