Flood Risk Guayaquil

Home , Babahoyo, Babahoyo River, Guayas River, Gulf of Guayaquil

Final Report

A critical analysis on inundations

Augustus-November 2016

Team: Supervisors: J.G. Stenfert 4098366 Dr. ir. E. Mosselman TU Delft, Deltares R.M. Rubaij Bouman 4169603 Dr. ir. M. Arias Hidalgo ESPOL–FICT R.C. Tutein Nolthenius 4155807 Ir. J. van Overeem TU Delft S. Joosten 4174070

Preface

This report concludes our multidisciplinary project written as a part of the master program Hy- draulic Engineering at Delft University of Technology (TU Delft). The project took place between August and November 2016 in the city of Guayaquil, Ecuador. The project has been written under the supervision of the department of Hydraulic Engineering at the TU Delft, the faculty ’Ingenieria en Ciencias de la Tierra’ at Escuela Superior Politecnica del Litoral (espol) and Deltares. For three months we have had the opportunity to experience the lifestyle and culture of Ecuador. In the first place we want to thank the people who directly enabled us to start the project in Guayaquil. Pri- marily, we thank dr. ir. Erik Mosselman for both his help with the organisation of the project from the Netherlands and the supervision during our stay in Guayaquil. Secondly, we greatly thank our supervisor and host dr. ir. Mijail Arias Hidalgo. Without his help we would not have been able to execute the project the way we did. We acknowledge him for his great hospitality, the excursions to show us the culture of his country, translating during several interviews and of course his academic supervision during the project. Furthermore, we would like to thank ir. Jan van Overeem for his help during the preparations of the project and his overall supervision. We would also like to thank ir. Anke Becker and dr. Arthur van Dam from Deltares in their support using the Delft3D Flexible Mesh software. Finally, we would like thank our dear friend and project-associate René van Meerkerk who at the very last moment had to decide not to join us to Guayaquil. He has made a big effort during the preparations of the project and we certainly missed him here in Guayaquil.

Guayaquil, November 2016. Joost Stenfert Roland Rubaij Bouman Raoul Tutein Nolthenius Stan Joosten

Abstract

Despite several researches about the hydrological and hydrodynamic system of the Guayas region, elementary insight of the total system was lacking. Therefore, the purpose of this study was to create a general overview regarding floods. Besides, basic solutions are proposed for preparing Guayaquil against floods which might be present in the future. From August till November the project team researched this topic by starting with a thorough analysis of the hydrological and hydrodynamic system and thereby interviewing many stakeholders within Guayaquil. Afterwards, several solutions concerning different major problems within the system have been conceived and relative effects have been modelled in Delft3D-FM and ArcGIS.

Several possible measures are proposed to challenge the rising sea level and more severe weather conditions which might be present in the future. Relative changes concerning implementing measures are modelled and discussed. Idem, existing articles on the estuary system are reviewed.

It can be concluded that an integral solution is required on measures against current flood problems. To protect the entire city against floods, governmental institutions must share knowledge and ideas. In addition, only a combination of a solution for better drainage and improved flood defences will prepare Guayaquil for more extreme weather events.

iii

Contents

List of Figures vii

List of Tables ix

1 Introduction 1

2 Approach and Methodology 3 2.1 System analysis ...... 3 2.2 GIS modelling ...... 3 2.3 Hydrodynamic modelling ...... 3 2.3.1 Boundary conditions ...... 3 2.3.2 Modelling situations ...... 4 2.4 Stakeholder analysis ...... 4 2.5 Formulation of design conditions ...... 5 2.6 Identiﬁcation and evaluation of possible measures ...... 5

3 Results 7 3.1 System analysis ...... 7 3.1.1 Literature review ...... 7 3.1.2 Data analysis ...... 13 3.2 GIS modelling ...... 14 3.3 Hydrodynamic modelling ...... 15 3.3.1 Amplification of tide ...... 15 3.3.2 Influence of river discharges ...... 15 3.3.3 Influence of Sea Level Rise ...... 16 3.4 Stakeholder analysis ...... 17 3.5 Formulation of design conditions ...... 18 3.5.1 Design water level ...... 18 3.5.2 Design discharge ...... 19 3.5.3 Design precipitation ...... 19 3.6 Identification and evaluation of possible measures ...... 20 3.6.1 Measures considering stormwater system ...... 20 3.6.2 Measures considering flood defence ...... 23 3.6.3 Evaluation ...... 28

4 Discussion 29

5 Conclusions and recommendations 33

v 5.1 Conclusions ...... 33 5.1.1 Required measures ...... 33 5.1.2 Future measures ...... 33 5.2 Recommendations ...... 34

Bibliography 35

A System analysis 39

B Model outcomes 49

C Stakeholder analysis 53

D Design conditions 57

E Possible measures 63

F Article reviews 67

vi List of Figures

2.3.1 Map of Delft3D-FM model ...... 4

3.1.1 Urbanization of Guayaquil [Jimenez and Matamoros, 2009] ...... 7 3.1.2 Overview of the estuary [Google, 2016a] ...... 7 3.1.3 Averaged monthly precipitation in Guayaquil ...... 9 3.1.4 Sea Level Rise in Latin America cities [Miller, 2009] ...... 11 3.1.5 Discharge Quevedo river during the El Niñophenomena [Xinqiang et al., 2015] . . . . . 11 3.1.6 Simplified intrusion scheme [Pietrzak, 2016] ...... 12 3.1.7 Sketch of the effect of a narrower channel ...... 13 3.1.8 Average monthly discharge Guayas river between 1988 and 2012 ...... 13 3.1.9 Water levels Guayaquil in river Guayas ...... 14 3.2.1 Flooded areas due to sea level rise ...... 14 3.3.1 Tidal amplification within estuary ...... 15 3.3.2 Influence on water levels due to different discharges ...... 15 3.3.3 Tidal asymmetry due to sea level rise ...... 16 3.3.4 Influence in water levels due to different scenarios ...... 16 3.6.1 Possible storage area in Guayaquil [Draftlogic, 2016] ...... 21 3.6.2 Possible storage area within the sea branches [Draftlogic, 2016] ...... 22 3.6.3 Use of a check valve ...... 22 3.6.4 Example of permeable asphalt [TARMAC, 2016] ...... 23 3.6.5 Example of green tiles [Grass Concrete Ltd., 2016] ...... 23 3.6.6 Position of levees and barriers [Google, 2016a] ...... 24 3.6.7 Possible barrier locations in the river Guayas [Google, 2016b] ...... 25 3.6.8 Possible location of barrier 2 [Google, 2016b] ...... 25 3.6.9 Modelled time series at Guayaquil using a discharge with a return period of 100 years . 26 3.6.10Modelled time series at Guayaquil using a discharge with a return period of 200 years . 26 3.6.11Effect on the main channel [Drawing by E. Mosselman, in Havinga, 2014] ...... 28 3.6.12Potential location of a bypass [Google, 2016b] ...... 28 3.6.13Side channel effects further downstream ...... 28

A.1.1Tide during observation [Mobile Geographics, 2016] ...... 39 A.1.2Field observations 09-09-2016 ...... 40 A.1.3Field observations 2-10-2016 ...... 40 A.1 Elevation of Guayaquil provided by Interagua ...... 41 A.1 Wind direction and speed [SuárezChanguán,2010] ...... 42 A.1 Stormwater system in Guayaquil provided with Interagua ...... 43 A.1 Cartoon of the El Niñophenomenon ...... 44

vii A.2 Effected zones by El Niñophenomenon 1982-1983 [Xinqiang et al., 2015] ...... 45 A.3 Effected zones by El Niñophenomenon 1997-1998 [Xinqiang et al., 2015] ...... 46

B.1 Inﬂuence of dam on water level in sea branch ...... 50 B.2 Water levels at Guayaquil ...... 50 B.1 Tidal current velocity over a tidal cycle (1) [Barrera Crespo, 2016] ...... 51 B.2 Tidal current velocity over a tidal cycle (2) [Barrera Crespo, 2016] ...... 51

D.1 Water levels Guayaquil in river Guayas ...... 59 D.2 Filtered water levels Guayaquil in river Guayas ...... 59 D.3 The Gumbel exceedance graph of water level ...... 60 D.1 Frequency curve discharge ...... 61 D.1 Frequency curve precipitation ...... 61 D.2 idf analysis [emapag-ep - Interagua, 2016] ...... 62

E.1 Considered city area [Draftlogic, 2016] ...... 63 E.1 Floating house [Cherry Mortgages, 2016] ...... 65 E.1 Inlet of the high water channel Veessen-Wapenveld [Dutchwatersector, 2013] ...... 65 E.2 Overview of the high water channel Veessen-Wapenveld [Dutchwatersector, 2013] . . . . 65

F.1 Part of 20 cities with highest loss in 2050, assuming sea level rise of 20 cm and maintaining ﬂood probability [Hallegatte et al., 2013] ...... 68 F.1 Basin area of Guayas river [Twin2Go, 2016] ...... 68 F.2 Closure of barrier proposed by cispdr [Xinqiang et al., 2015] ...... 70

viii List of Tables

3.5.1 Return period of 24 hours storm ...... 19 3.6.1 Evaluation/Summary table of possible measures ...... 28

D.1.1Reference projects storm surge barriers ...... 57 D.1.2Probability of Exceedance for different design lives and return periods ...... 58 D.1.3Design requirements for different components in a flood defence system ...... 58 D.2.1Discharges at different return periods [Xinqiang et al., 2015] ...... 60 D.3.1Return period of 24 hours storm [emapag-ep - Interagua, 2016] ...... 61

1 Introduction

Due to climate change more severe weather conditions might be present in the future in large parts of the world [IPCC, 2013][Cai et al., 2014]. In Ecuador, Guayaquil urbanized rapidly without proper planning. Therefore, the city exerts a lot of pressure on its surroundings. Nowadays, the city suffers from floods due to high precipitation rates and high water levels within the sea branches (locally known as ’esteros’) and at the Guayas river. The question is how to respond on these higher risks. Several studies show that although the protection against flood increases the magni- tude of societal losses would not undeniably decrease when floods do occur [Hallegatte et al., 2013] [Aerts et al., 2008].

In this research an overall analysis is executed on floods and its critical points within the Guayaquil area. Problems and their associated solutions concerning flooding are specified.

Several studies have been carried out considering the Guayaquil estuary by both local and foreign researchers. Current analyses about the flooding of Guayaquil is often very pragmatic in terms of finding solutions for flood safety. Thereby, simplistic perspectives are given to provide a warning for policymakers. Unfortunately, there is still a lack of elementary insight of the total hydrological and hydrodynamic system of Guayaquil.

The currently proposed interventions might be limited due to the lack of a thorough integral study on the hydrological and hydrodynamic system. In that regard, the following questions will be addressed in this report:

• What are the critical points within the hydrological and hydrodynamic system of Guayaquil?

• What measures should be taken to suﬃciently decrease societal risk by ﬂoods in the future?

• What are the inﬂuences of changing weather conditions?

These questions can be answered by looking into the occurrence of different events in the Guayaquil basin. Combinations of the El Niñophenomenon, sea level rise, tidal fluctuations and high precipitation peaks may lead to critical water levels around the city of Guayaquil and could cause higher societal risk in the future. With the help of GIS modelling critical points within the city can be determined. Knowledge on hydraulic engineering will help us to provide possible measures. Be- sides, with Delft3D-FM modelling the influences of changing weather conditions on the Guayaquil estuary can expose possible future changes.

2 Approach and Methodology

2.1 System analysis

To fully understand the processes in the area of study the total system has been analysed by means of a literature review. Amongst others, the location, topography, current state of ﬂood defences, climate and hydrological and hydraulic conditions of the city are considered. Where needed, extra information and data has been gathered with the help of interviews with experts and site visits.

2.2 GIS modelling

In order to determine which areas of the city will be flooded, ArcGIS is used. Interagua provided data which is implemented in an ArcGIS model (see appendix B.1). In ArcGIS, a distinction is made between rural and urban areas. With future prospects, the influence of sea level rise has to be taken into account. Different sea level rise scenarios are used, which are +3.5 msl plus 20 cm, 40 cm and 60 cm (see figure 3.2.1). Note that +3,5 msl is a water level with a return period of 200 years. In 100 years 60 cm sea level rise can be expected (see section 3.1.1.8).

2.3 Hydrodynamic modelling

To obtain more information on the estuary system, Delft3D Flexible Mesh modelling is used. Flex- ible Mesh refers to the ﬂexible combination of structured and unstructured grids. This leads to more freedom for implementing diﬀerent situations.

A Delft3D Flexible Mesh model has been used by Deltares and P.D. Barrera Crespo for modelling the Guayas estuary (see ﬁgure 2.3.1). Calibration of the model has shown that the reality is well presented. Although most measured data match with the results of the model, there are some discrepancies at some places. Exact water levels for design cannot be taken from the model, but a study with relative changes within the system is possible.

2.3.1 Boundary conditions For the hydrodynamic model time series are taken for boundaries at the ocean side. Since the mouth of the estuary is very wide and tide comes from the North, a gradual changing tide along the boundary is selected. At the northern boundary of the system, discharge boundaries are given at the Daule river (at St. Lucia) and the Babahoyo river (at Babahoyo). In reality however, other small rivers contribute to the discharge as propagating downstream. Relevant rivers are included within the boundary conditions. Spring tide is used to mimic the highest possible water level outcomes.

3 CHAPTER 2. APPROACH AND METHODOLOGY Flood Risk Guayaquil

Figure 2.3.1: Map of Delft3D-FM model

2.3.2 Modelling situations The influence of changing boundary conditions has been evaluated within this report. Due to changing climate conditions sea levels and river discharges might change. These are both used as boundary conditions within this model and are important factors within the estuary system. Besides, the influence of a barrier (proposed within this report) on water levels in Guayaquil has been evaluated and the amplification of the tidal propagation has been analyzed.

2.4 Stakeholder analysis During our study on flood risk in Guayaquil a fair amount of research has been done on the politics considering decision making in civil works. Little literature is available on policies considering flood risk and hydraulic engineering strategies in the region. Therefore, we decided to increase our knowledge by interviewing different parties considering inundations in the city of Guayaquil. The interviews were initially focused on understanding the hydraulic and hydrological system in the area of study. However, it came to notice that a variety of political issues caused inefficient policy and decision making. In the interviews we carefully tried to uncover some of the problems and tried to understand which intentions and visions each stakeholder had. From these interviews often different views on the distribution of responsibility of flood mitigation and relief became apparent. However, a common understanding was found on that something might have to change when it comes to making policies and long term strategies.

The following people have been interviewed to a greater or lesser extent on current and future policies on ﬂood risk. Please note that the interviewed people are in no way liable for the statements within our report. Inaccuracies could be present by misinterpretation and translation errors.

• Dr. Maria del Pilar Cornejo-Grunauer, Former minister of Secretaria de Gestion de Riesgos.

• Juan Carlos Bernal, Water Supply Manager at Interagua.

4 CHAPTER 2. APPROACH AND METHODOLOGY Flood Risk Guayaquil

• Iv´anRivera-Garc´ıa,Design Manager at Interagua.

• Ing. Juan Antonio Ramirez Ponce, Director de Riesgos at the municipality of Guayaquil.

• Dr. Ing. Mijail Arias Hidalgo, Associate Professor & Researcher at faculty of earth sciences at espol

• Msc. Otto de Keizer, Senior Advisor Water Resources and Coordinator Latin America at Deltares.

• Dr. Eduardo Zambrano, Climate services at ciifen.

Furthermore, the parties that might be involved in civil works in the region have been indicated and analysed to determine in what extend these parties are responsible for their share flood mitigation and relief. Within this stakeholder analysis two ministries and more local governmental institutions, for example the Prefecture of the Guayas Province, the Municipality of Guayaquil and its subdivision emapag are considered. Furthermore, the institutions Interagua, The Escuela Superior Politécniadel Litoral (espol), Instituto Oceanográficode la Armada (inocar), Instituto Nacional de Meteorologia e Hydrologia (inamhi) and Changjiang Institute of Survey, Planning, Design and Research (cispdr) are elaborated on. 2.5 Formulation of design conditions From studies on flood interventions and interviews with different stakeholders, a variety of return periods for design parameters came up. The return periods regarding the discharge of certain parts of the stormwater system is currently 1 to 5 years where in other parts it is 10 to 25 years (I. Rivera-Garc´ıa, personal communication, 2016). Other statements are made on the current protection level of the river banks. The design load has a return period varying from 25 to 50 years [Xinqiang et al., 2015] (P. Cornejo-Grunauer, personal communication, 2016). An analysis is made on the correlation of design life, probability of exceedance and return periods. Furthermore, different reference projects are analysed considering these three factors. From these analyses an acceptable return period for design conditions has been determined. 2.6 Identification and evaluation of possible measures Risk is defined as probability times consequence. The risk will be decreased by reducing the probability of failure or the consequences. There are two main components within the solution: lowering water levels and improving drainage of high precipitation rates. Some possible measures are more urgent than others since problems are already present. Other measures will prepare the city for more hazardous events in the future.

The main goal for measures considering the stormwater system is to improve the way precipitation is collected, temporarily stored within the city and drained into the river and sea branches. By improving the system, mainly the probability of a ﬂooding will be reduced.

Measures considering flood defence are proposed to decrease the severity of floods within the city. Two types of solutions can be used. First, lowering the water levels within the sea branches and rivers. Second, improve the defense of the riverbanks to decrease the probability of flooding.

3 Results

3.1 System analysis

3.1.1 Literature review The city of Guayaquil is located at the west coast of Ecuador. Due to the colonial history, the city originated close to the Guayas river that mouths into the Pacific Ocean. The waterway was used for trading, transportation and communication. After 3 attempts and relocations, Guayaquil was founded in 1537. It is the capital of the Guayas Province and also the largest city in Ecuador. Guayaquil is considered to be the economic heart of the country due to the port. The bigger part of the country’s import and half of the export heads to the local harbor (’Puerto Maritimo’) and passes through the Gulf of Guayaquil. Since the 1960s, the city was subjected to major expansions. The expansions are mostly spacial and there are hardly any high-rise buildings present. Thus, rural areas get urbanised fast. This introduces great pressure on the surrounding hydrodynamic system and affects the safety against floods in the city. An overview of the urbanization and the scope for solutions is given in figures 3.1.1 and 3.1.2 respectively.

Figure 3.1.1: Urbanization of Guayaquil Figure 3.1.2: Overview of the estuary [Jimenez and Matamoros, 2009] [Google, 2016a]

Ecuador is situated on the boundary of the Nazca and the South American plate. Guayaquil has

7 CHAPTER 3. RESULTS Flood Risk Guayaquil many low lying areas, some parts are under +4 m relative to MSL. Other parts are up to 400 m on the west side at Cerro Blanco, part of the hilly ridge of Chong´on-Colonche. A map with elevations of the city of Guayaquil is given in appendix A.2. 3.1.1.1 Daule-Peripa Dam The Ministry of water (senagua), constructed the Daule-Peripa dam which was ﬁnished in 1987. The dam is build far upstream in the Daule river and has the following purposes [Arriaga, 1989]:

• Flow regulation, water storage for irrigation and power generation (maximum of 213 MW).

• Control ﬂoods by means of dikes and additional constructions for ﬂow regulations.

• Transportation of water from surplus areas to regions with a lack of water resources.

• Soil protection from erosion and consistent forest resources management for the protection of the environment.

• Preventing salt intrusion at the water intake of Guayaquil (26 km north of the city)

The reservoir has a capacity of 6 km3. During wet season water can be collected, which could be used during dry periods[Saavedra Mera et al., 2014]. 3.1.1.2 Daule and Babahoyo river The Daule and the Babahayo river are the rivers entering the city from the north, forming the Guayas river in front of the city. Thereby, the Vinces river is contributing significantly to the Babahoyo river. Further upstream, smaller rivers connect with the two rivers, which results into a large catchment area. The Daule river basin covers an area of 13.280 km2 and has a contribution of 40 percent to the Guayas river discharge. The Babahoyo river has a basin of 18.220 km2 which completes the other 60 percent contributing to the discharge of the Guayas river. During wet season these percentages can be slightly different. The Guayas river has a mild slope (less than 1 · 10-5). Due to the large catchment areas, more extreme conditions in the future might lead to large effects on the river discharge [Castro, 2009]. 3.1.1.3 Current flood defences Little is known about the current levels of flood safety of structures in and around the city of Guayaquil. To gain more insight in the present flood defence system in the city, observations have been carried out in the field. The current flood defence can withstand water levels with a return period of 1 in 30 to 40 years (P. Cornejo-Grunauer, personal communication, 2016). From observations (see appendix A.1) it seems that the protection of the river banks is not the responsibility of one institution. Although the problems seem to be solved locally and the solutions are not uniform over the whole river, it could be the responsibility of one party. 3.1.1.4 Earthquakes and Tsunamis On 16 April 2016, an earthquake took place at Esmeraldas, Ecuador (at the northern coast). In Guayaquil, few structures collapsed. The damage of this earthquake could be assigned to poorly designed constructions and not particularly to the severeness of the earthquake.

The effects of possible tsunamis can be neglected for both locally and far generated earthquakes, as stated in a research paper of M. Ioualalen et al. Although a large earthquake might occur, it would not lead to a tsunami with significant flooding. However, it might be important to design future measures which can withstand earthquakes, especially since failure of structures in combination

8 CHAPTER 3. RESULTS Flood Risk Guayaquil with high water levels might result in major damage [Ioualalen et al., 2014]. Further elaboration can be found in appendix A.3. 3.1.1.5 Climate The climate of Guayaquil is classified as a dry tropical semi - humid climate, with a wet (rainy) season from approximately January to April and a dry season from circa June to November. Dry season has average temperatures which exceed 24 degrees Celsius. During wet season, average temperatures range from 26 to 28 degrees Celsius [SuárezChanguán,2010]. The average annual precipitation in Guayaquil is equal to 1068 mm, whereof over 80 percent falls during the wet season as illustrated in figure 3.1.3. Heavy rainfall in short periods combined with the rapid and uncon- trolled urbanization cause severe floods [Hollis, 1975]. Some days, precipitation rates can get as high as 100 mm per day [INOCAR, 2016]. Important to notice is that such precipitation rates do not have to be evenly distributed in time and in space. In Guayaquil micro climates are present.

Furthermore, at the inner part of the estuary the wind does not seem to play a major role on the hydrodynamics. A short analysis can be found in appendix A.4.

Figure 3.1.3: Averaged monthly precipitation in Guayaquil

3.1.1.6 Stormwater System During severe precipitation, Guayaquil can flood due to poor drainage. At the moment, there is a stormwater system in some parts of the city. Some parts are subsided and designed poorly and therefore not working properly (P. Cornejo-Grunauer, personal communication, 2016). The low lying areas in the city have major problems with drainage. In addition, most of these areas are currently paved (asphalt, concrete, tiling, etc), which leads to less infiltration resulting in faster and higher runoff.

In appendix A.5, the current stormwater system can be observed. Only few parts of the system have been designed with a return period of 10 or 25 years. However, most parts only have been designed to handle return periods of 1 to 5 years. At the end of the stormwater system there are often open outlets, which can be blocked by high tide. High water levels also cause noticeable sedimentation and salt intrusion within the pipes, especially at the northern river shore (Guayas and Daule Rivers). During extreme high tides, parts of the city can even be ﬂooded through the

9 CHAPTER 3. RESULTS Flood Risk Guayaquil stormwater system due to a negative water level gradient.

Trash in the stormwater system causes poor runoff. Every year the municipality cleans the stormwater system from October until December as a periodical prevention procedure. They do not only clean it, but also destroy and remove illegally build structures that are constructed within the drainage system. In this way higher runoff is enabled during the wet season (J.A. Ramirez Ponce, personal communication, 2016). In addition, the government regulate new laws in which people are prohibited to live in flood prone areas. 3.1.1.7 Tide dominated system The Guayas river mouths into an estuary which is categorized as a tide dominated system. Char- acteristics of such a system are wide rivers and small islands near the mouth of the river [Stive and Bosboom, 2015]. The entrance of the estuary is more than 200 km in width and convergences further upstream. The tidal wave strengthens as it goes upstream, because convergence has a larger effect than friction [Barrera Crespo, 2016, p.24]. This can be observed up to 120 kilometers upstream of the mouth of the estuary, but it is no longer noticeable beyond the towns of Babahoyo (120 km inland) and Daule (60 km inland). The latter is due to the regulation of the Daule-Peripa Dam. [Castro, 2009]. The tidal wave also creates a standing wave character as it travels upstream to Guayaquil. There is a phase lag of 1 hour between high-water and high-water-slack, which remains constant along the Guayas. The tidal system is flood dominant. This implies that the rising period is faster than the falling period and that maximum flood velocities are higher than maximum ebb velocities. The current velocities of one tidal cycle in the estuary are visualised in appendix B.3. 3.1.1.8 Relative Sea level Rise In the recent past the awareness regarding sea level rise increased significantly [Hallegatte et al., 2013]. It is of importance to investigate what the effect of sea level rise could be on Guayaquil in order to come up with solid measures.

Due to many reasons, sea level rise occurs on different time and spatial scales. Sea level rise can be divided into global and local sea level rise. Warming of the Earth causes water to expand and the glaciers to melt which both lead to global sea level rise. Although globally the sea level has been rising 3.5 mm per year since 1993, it differs locally due to subsidence, global sea level fluctuations, winds, ocean circulation and water density [Miller, 2009]. Subsidence can be divided in several components as well, for instance mineral extraction, seismicity and glacial rebound. Relative sea level represents the changes in both vertical land movements and the changes in the eustatic ocean level [Warrick and Oerlemans, 1990].

At the moment, no research is present on subsidence at Guayaquil. According to measurements at La Libertad (at the tip of the Peninsula of Santa Elena, the westernmost point of Ecuador), the country faces one of the biggest sea level rises per year, in comparison with other locations along the west coast of South America [Miller, 2009]. In figure 3.1.4, it can be observed that during the last 50 years an average absolute rise of 6 mm/year occurred. Despite its distance from the study area, observations from La Libertad can still be used as indication for Guayaquil since tide is present there. 3.1.1.9 The El Niñophenomenon The El Niñophenomenon is known as one of the largest (global scale) and most severe climatic events. In contrast with other natural hazards, the El Niñophenomenon is not directly visible or

10 CHAPTER 3. RESULTS Flood Risk Guayaquil

Figure 3.1.4: Sea Level Rise in Latin America cities [Miller, 2009] noticeable. It can cause heavy rainfalls, prolonged droughts and major ﬂoods especially in Latin America and Australia. Although the El Ni˜nophenomenon is still not very well understood, main drivers of such an event are explained in appendix A.6.

The El Niñophenomenon is hard to predict due to the fact that both strength and return period are far from constant. On average an event happens every 4 years, but the range of succession is between 2 and 7 years [Pietrzak, 2015, p. 140-145]. In 1972 there was a large El Niñophenomenon. Besides severe precipitation rates, the El Niñophenomenon led to a rapid increase of 34 cm sea level in a few months in the east Pacific until a maximum of 22 cm above MSL [Wyrtki, 1977].

Furthermore, a modeling research stated that there will be an increase in El Ni˜nophenomena frequency due to surface warming over the Eastern Equatorial Paciﬁc. Heating of this water column takes places faster than in the surrounding ocean waters. This facilitates more convection in the eastern equatorial region [Cai et al., 2014].

Large historical inundations During the El Niñophenomena in 1982-1983 and 1997-1998, large floods occurred in the Guayas region. The precipitation rates during these periods were higher than the ordinary averaged values, which led to higher discharges within the rivers (figure 3.1.5). Both El Niñophenomena had their biggest impact on the middle- and low lying areas of the Guayas Province, which includes Guayaquil (see appendix A.6.1) [Xinqiang et al., 2015].

Figure 3.1.5: Discharge Quevedo river during the El Ni˜nophenomena [Xinqiang et al., 2015]

11 CHAPTER 3. RESULTS Flood Risk Guayaquil

In 1982-1983, the precipitation rates in local areas reached values up to 60% more than average. In addition, the river Vinces processed a 210 times higher volume than average in the same period. Almost all Guayas basins were ﬂooded and big disasters followed. The caused damage of this El Ni˜nophenomenon was hard to quantify [Xinqiang et al., 2015].

The El Ni˜nophenomenon of 1997-1998 had around 75% higher precipitation than the average precipitation in one year. The national losses were estimated to be around 4 billion usd [Xinqiang et al., 2015].

3.1.1.10 Salt intrusion Tides lead to changes in ocean water levels. Due to these relatively fast changes a water level gradient exists and thereby salt water can intrude into the river. In ﬁgure 3.1.6, a simpliﬁed example is presented [Pietrzak, 2016]. How ocean water intrudes into the river system, is depending on the bed slope of the river and the amplitude of the tide, in this case respectively low and high. Therefore, salty water intrudes far into the system. Salt intrusion can lead to damage to agriculture, water intakes and the environment at large [Uzochukwu et al., 2009, p.98].

Figure 3.1.6: Simpliﬁed intrusion scheme [Pietrzak, 2016]

3.1.1.11 Sedimentation of the estuary At the moment, the Gulf of Guayaquil is exposed to sedimentation issues due to natural events and human interventions within the estuary. The El Niñophenomenon, deforestation, development of shrimp farms, construction of a bridge and the placement of a dam upstream all have influence on the situation. The estuary is flood dominant during normal conditions and therefore imports sediment. When higher discharges are present within the Guayas river, the characteristics of the system could shift from flood dominance to ebb dominance [Barrera Crespo, 2016].

Below, several things are listed why sedimentation would be a problem for the system. In appendix A.7 causes of sedimentation are described.

• The sedimentation within the Guayas, Daule and Babahoyo river harms the navigability.

• Sedimentation along the channels may cause an increase in flood risk for low lying areas around the margin of the rivers. The decreased depth throughout a large part of the river might reduce the carrying capacity. Furthermore, the reduced width of the river could cause backwater effects that might increase flood risk as well. A narrower channel (2) leads to a higher equilibrium depth, as can be seen in the lower part of figure 3.1.7. This difference in equilibrium depth between the situation upstream (1) and downstream (3), may lead to a backwater effect and thus increases flood risk. It can be argued what the influence is, when tide is present.

12 CHAPTER 3. RESULTS Flood Risk Guayaquil

Figure 3.1.7: Sketch of the eﬀect of a narrower channel

3.1.2 Data analysis

3.1.2.1 Water levels and discharge Discharge data is available at 5 different gauging stations, from which four are situated along the Babahoyo river system and one at the Daule river. The monthly average discharges of these stations span from 1883 until 2012 [INAMHI, 2012]. The Daule-Peripa Dam (see section 3.1.1.1) has large influence on the perception of the data. In order to have a valuable indication of the discharge, the data before construction of the dam is not considered. In figure 3.1.8, difference between the El Niñophenomenon and the normal discharge is clearly visible [Barrera Crespo, 2016].

Figure 3.1.8: Average monthly discharge Guayas river between 1988 and 2012

The average discharge in the wet season is 970 m3/s for the Babahoyo and 445 m3/s for the Daule river. In the dry season these discharges are signiﬁcantly lower, namely 115 m3/s for the Babahoyo and 125 m3/s for the Daule river.

The water level near Guayaquil is mainly determined by the tidal wave travelling into the estuary. With the use of data provided by Interagua it is found that during springtide the amplitude near Guayaquil is usually around 2 meters (see ﬁgure 3.1.9).

13 CHAPTER 3. RESULTS Flood Risk Guayaquil

Figure 3.1.9: Water levels Guayaquil in river Guayas

3.2 GIS modelling

Under the different circumstances proposed in section 2.2, the total flooded urban area is approximately between 30 and 53 km2. As can be seen in figure 3.2.1, the southern part of Guayaquil is most vulnerable because the floods are mainly caused by the sea branches. Although this is a reasonable approximation there are some remarks, which are elaborated in appendix B.1.

Figure 3.2.1: Flooded areas due to sea level rise

14 CHAPTER 3. RESULTS Flood Risk Guayaquil

3.3 Hydrodynamic modelling 3.3.1 Amplification of tide In figure 3.3.1, it can be observed that the tidal amplitude amplifies when travelling into the system (see section 3.1.1.7). This is the case for the water levels in both the sea branches and the Guayas river.

Figure 3.3.1: Tidal ampliﬁcation within estuary

3.3.2 Influence of river discharges Discharges differ significantly during dry and wet season. Higher discharges may lead to differences in flood or ebb dominance [Barrera Crespo, 2016, p. 35]. According to the model, the discharge can have significant influence on the water levels in Guayaquil (see figure 3.3.2). As can be observed, the shape of the time series becomes more skewed when the discharge increases. Although the difference is small, it confirms that higher discharge will evolve towards a more ebb dominant system.

Figure 3.3.2: Inﬂuence on water levels due to diﬀerent discharges

Figure 3.3.2 shows that at a discharge with a return period of 200 years (see section 3.5.2) the water

15 CHAPTER 3. RESULTS Flood Risk Guayaquil level at Guayaquil can be at least 60 cm higher compared to the mean wet season discharges. Higher discharges result in higher water levels further downstream. Note that this scenario is modelled with spring tide. 3.3.3 Influence of Sea Level Rise We analyzed the effect of sea level rise on the estuary, partly by modelling and partly by means of theory. As described in section 3.1.1.7, tidal amplification is present within this estuary. From the Delft3D-FM model it can be observed that sea level rise will lead to a higher tide within the city. Due to higher water levels, friction will have less influence on the tidal wave and therefore the amplitude will increase more. The tidal amplitude amplifies more during high tide than during low tide (see figure 3.3.3). When the tidal asymmetry will increase, more sediment might be imported due to sea level rise [Stive and Bosboom, 2015].

Figure 3.3.3: Tidal asymmetry due to sea level rise

In figure 3.3.4, different sea level rise scenarios are given. 20, 40 and 60 cm sea level rise have been modelled (similar to GIS modelling) with a mean river discharge and during spring tide. In addition, 50, 70 and 90 cm show the same sea level rise with an El Niñophenomenon present. When the El Niñophenomenon is present, the sea level increases about 30 cm (see section 3.1.1.9) and river discharges increase significantly. Within this scenario discharges are used with a return period of 200 years.

Figure 3.3.4: Inﬂuence in water levels due to diﬀerent scenarios

16 CHAPTER 3. RESULTS Flood Risk Guayaquil

3.4 Stakeholder analysis Firstly, all stakeholders mentioned in section 2.4 are analysed to determine their relation with ﬂood mitigation and relief. The full analysis is given in appendix C. Furthermore, new insights were obtained considering the problems by means of the interviews. Although the interviews were based on questions to understand the hydraulic and hydrological system also several political issues were discussed.

By law, public services considering drainage and irrigation are established in national planning by senagua. However, the planning and execution is the responsibility of the autonomous decentralized provincial governments in accordance with their respective powers [Secretaria del Agua, 2014]. The acquisition of funds is done by the decentralized governments and can be partly collected at the diﬀerent ministries (e.g. The Ministry of Risk Management and senagua) and the development bank of Ecuador. It could be interpreted as follows: ”The ministry gives the tools for a policy but decentralized governments have to implement it” (P. Cornejo-Grunauer, personal communication, 2016). Furthermore, from the series of interviews it came to notice that sanctions can be imposed upon the decentralized governments if policies are not followed. However, it was not clear to us what the nature of these sanctions is and on what base they are appointed.

Although the above mentioned system might sound promising, some conflicts seem to arise. The national and different local governments are chosen independently and therefore the priorities considering flood defence are not always aligned. We learned that especially the province of Guayas and the municipality of Guayaquil do not work closely together on for instance policies related to the river Guayas due to political disagreements. Besides, in politics certain measures especially in flood mitigation are not very popular by the inhabitants. As the inhabitants elect both the municipality and the mayor, the politicians seem to be careful in renewing their views considering unpopular policies. For instance, in three different interviews the consideration of extension of the drinking water system versus the improvement of the stormwater system is discussed. Although the people suffer from the inundations that can occur during wet season (especially during the El Niño phenomenon) the more popular thing to do is extending the drinking water network because it has instant value for the inhabitants. The inundations do not occur all year round and are easily forgotten when dry season begins, therefore development of the improved drainage is often postponed (P. Cornejo-Grunauer, personal communication, 2016) (I. Rivera-Garc ´ıa,personal communication, 2016) (J.A. Ramirez Ponce, personal communication, 2016). As in many countries around the globe often short term or ”visible” solutions have a higher political value.

Moreover, we have noticed that sometimes a lack of long term policy and future perspective on city spacial planning might cause intensified and more frequent problems. We have for example heard about plans to transform Urdesa, one of the low-lying flood prone areas of the city, from residential to commercial area. This would mean an increase of crowdedness and therefore intensified water consumption. However, appropriate measures relating to improved stormwater systems and increased human risk in case of an emergency are not considered.

On the other hand, lots of improvements are obtained in the past few years. For instance, new laws are implemented by the national government considering the illegal occupation of the sea branches. The municipality and mayor recognize the problem and started relocating the people by new regulations and enforcement strategy. Furthermore, no deaths occurred during the last ﬂood- ing and drainage channels are getting cleaner, less sedimentation and new regulations are made in

17 CHAPTER 3. RESULTS Flood Risk Guayaquil order to prevent a worse situation (P. Cornejo-Grunauer, personal communication, 2016). From an interview at the municipality we obtained information about a new resident unit in ﬂood management. The unit is only four years old and involves all problems related to rainfalls and high water levels in the estuary. The unit is assigned to evaluate the (hazardous) events and support in the development of solutions. Additionally, the municipality started a development plan in which they promote the vertical expansion of the city instead of horizontal expansion (J.A. Ramirez Ponce, personal communication, 2016). Lastly, at Interauga several developments are made including a master plan where the current system is evaluated and a handbook (best practices) is made with studies on, and possible measures against, the current problems.

However, the lack of available budget causes an ongoing conﬂict (according to experts and researchers) on what projects need to be done and what projects are actually executed (I. Rivera- Garc ´ıa,personal communication, 2016) (J.C. Bernal, personal communication, 2016). Concluding: We tend to think that the long term views on ﬂood risk are more and more implemented in the protocol for spacial planning but are not yet considered in all decisions.

From the interview at ciifen the main concern is the life span of upcoming projects on flood mitigation and relief. It was made very clear that solutions to reduce inundations should be assessed on the most up to date information regarding climate change, sea level rise and the El Niño phenomenon. Governmental organisations and consulting firms should therefore seek advice from institutions like ciffen.

As a final statement we would like to emphasize the importance of a integral solution for the city of Guayaquil. Not only when it comes to civil works but also in politics. It should be highlighted that almost all interviewed parties plead for a solution that is supported by all different stakeholders. The different stakeholders should improve their relationship with one and another and should respect each others expertise. It is important that policy makers are advised by experts and decisions are made upon scientific reasoning. A good start would be a mutual understanding on the exact nature of the problems and responsibilities considering floods in Guayaquil by all different parties.

3.5 Formulation of design conditions The design return period is chosen as 200 years. This is rather low compared to reference projects. The design level is a trade oﬀ between costs and consequences if the structure fails. In Guayaquil, consequences might be lower if the structure fails. Besides, compared to the Netherlands, a certain amount of money in Ecuador might have more value compared to the Netherlands, since it is a larger part of the total GDP. The determination of the return periods are elaborated in appendix D.1.

3.5.1 Design water level The design water level has been determined from a dataset obtained by Interagua. The dataset has been obtained slightly downstream of the confluence of the Daule and Babahoyo river since 2009. With a Gumbell extreme value analysis it is found that the design water level with a return period of 200 years is msl + 3,07 m. This is further elaborated in appendix D.1.1. The design water level includes a moderate El Niñophenomenon in 2009. However, more severe El Niñophenomena were not present in the registered period. For that reason, a higher design water level might be advisable. cispdr used a water level of msl + 3,5 m. The water level which is elaborated by cispdr might have included more El Niñophenomena. Unfortunately, the data for the elaboration

18 CHAPTER 3. RESULTS Flood Risk Guayaquil of this value were not provided in their report. Since measured water levels have some uncertainty, the water level from cispdr with a return period of 200 years is adopted. 3.5.2 Design discharge The design discharge of the Guayas river is obtained from the data of cispdr. The data provides discharges at different cities adjacent to the Daule and Babahoyo river. For the Daule river, the discharge at St. Lucia is taken because this city is used as boundary condition in the Delft3D-FM model (see section 2.3). For the Babahoyo river however, the city Samborondónis chosen. This is done in order to include the discharge of the Vinces river within the boundaries. Note that for the Daule river only the discharges after the construction of the Daule-Peripa dam are considered (see section 3.1.1.1). For the determination of the river discharges with a return period of 200 year the data of the study of cispdr is extrapolated. It follows that the design river discharge of the Daule river (at St. Lucia) is 3904 m3/s and the Babahoyo river (at Samborondón)is 6286 m3/s. This is elaborated in appendix D.2.

3.5.3 Design precipitation The design precipitation is obtained from data provided by inamhi. One of the stations of inamhi, which registered the precipitation since 1959, is established near the airport of Guayaquil (02◦ 09 12 s, 79◦ 53 00 w). By using the Gumbel’s extreme value analysis the precipitation with a return period of 200 is elaborated (see appendix D.3). It depends on the measures which return period (50, 100 or 200 year) is taken. The precipitation rates belonging to the diﬀerent return periods are given in table 3.5.1. Note that these values are not bound to a interval of 24 hours, but could also fall in a shorter period of time. Furthermore, in 1998 the maximum registration of precipitation rates due to the El Ni˜nophenomena was 221.8 mm per day [emapag-ep - Interagua, 2016]. This is between the precipitation rates with the return periods of 50 and 100 years.

Return period [years] 50 100 200 Precipitation [mm/d] 214.3 237.5 263.5

Table 3.5.1: Return period of 24 hours storm

19 CHAPTER 3. RESULTS Flood Risk Guayaquil

3.6 Identiﬁcation and evaluation of possible measures The most important measures are elaborated within this chapter. For completeness, other considered measures are elaborated in appendix E. These can be divided into measures considering the stormwater system and considering ﬂood defence.

3.6.1 Measures considering stormwater system Several measures considering stormwater are proposed to decrease the amount and severity of floods within the city. The main goal is to improve the way precipitation is collected, temporarily stored and drained into the river and sea branches. By improving the system, mainly the probability of a flood will be reduced. 3.6.1.1 Possible storage areas During peak precipitation rates the runoff could be collected in storage areas. It is hard to find suitable areas in the urban area of Guayaquil, because constructing a storage area in an urban area has a huge social impact (J.A. Ramirez Ponce, personal communication, 2016). In some parts of the city, especially in the southern part, the groundwater level is reached at approximately 1 metre under the surface level (I. Rivera-Garc´ıa,personal communication, 2016). This must be considered when storage areas are designed.

At the moment, a ’cascade’ is being designed for the North Western part of the city. The area is hilly and therefore the water can temporally be stored at different levels. Due to gravitational forcing hardly any energy is consumed. Furthermore, runoff is distributed in both space and time, which prevents the valley to flood during peak precipitations rates. 3.6.1.2 Storage area in the city We proposed several storage areas as can be seen in figure 3.6.1. These storage areas are all low lying areas and are not far from the river (see appendix A.2). Therefore, these areas can easily be reached with drainage pipes and emptied when the peak precipitation has passed. Thereby, water can be drained to the Guayas river when low water is present. Furthermore, hardly any assets are present within these areas.

In the following list six possible areas are elaborated.

• Area 1: In the northern part of the city a large grassland is available near Santa Ines. Approximately 1,000,000 m2.

• Area 2: Near Santa Anes. Approximately 760,000 m2.

• Area 3: A stretch adjacent to the Daule river. Approximately 1,050,000 m2.

• Area 4: The new airport will be relocated to the western part of the city and therefore the old airport might be used as storage area in the future. Approximately 1,300,000 m2.

• Area 5: In the southern part hardly any large areas are available. Agricultural land could be used as temporary storage basins, especially because the area is low lying. Approximately 2,000,000 m2.

• Area 6: In the southern part of Guayaquil several smaller parts could be used as storage areas, which would approximately 1,100,000 m2 in total.

20 CHAPTER 3. RESULTS Flood Risk Guayaquil

Figure 3.6.1: Possible storage area in Guayaquil [Draftlogic, 2016]

A summation of all these areas leads to a total storage area of 7.1 km2. In appendix E.1, a rough calculation is given considering the required storage areas. The most difficult part is to transport the runoff towards the storage areas due to flat areas. Note that these areas can have multiple purposes. Most of the possible storage areas are positioned in the northern part of the city because these areas are not urbanized yet (figure 3.6.1). The municipality has to realize these storage areas on short notice or legally constrict any building activity, as otherwise, these areas will be urbanized as well (J.A. Ramirez Ponce, personal communication, 2016).

3.6.1.3 Roof tops Hardly any water is collected at residential places. By using gutters at rooftops combined with barrels to store water, the peak runoﬀ can be reduced. This storage of water by inhabitants will also create possibilities to use precipitation within households.

3.6.1.4 Sea branches as storage area The large sea branches in the city could be used as storage area when gates are constructed at the entrances of the branches, as can be seen in ﬁgure 3.6.6. In case of an extreme weather event, the gates will close at low tide which leads to lower water levels in the sea branches. This results in better runoﬀ possibilities and also an extra storage area (approximately 5.1 km2). The branches can be drained after high tide has passed. The storage area within the sea branches could be used in combination with the six areas mentioned in section 3.6.1.2.

3.6.1.5 Improved stormwater system In order to improve the system, the capacity of most canals and pipes has to increase. Further- more, an improved system has to be installed in a correct way. This means no negative slopes and

21 CHAPTER 3. RESULTS Flood Risk Guayaquil

Figure 3.6.2: Possible storage area within the sea branches [Draftlogic, 2016] minimal leakage. Increased monitoring of the canal system could prevent that people will illegally build structures in the stormwater system.

Pumping stations near the outlets of (temporary) storage basins and drainage pipes could be measures to overcome the blockage of runoff. Furthermore, there will be no tidal influence within the system and thereby no erosion and sedimentation. Another measure to overcome the tidal intrusion is check valves at the end of the stormwater system (see figure 3.6.3). These valves are relatively cheap and ensure the river water cannot intrude into the stormwater system when high water levels are present. However, sediment coming from the drained areas might still be present in the stormwater system.

Figure 3.6.3: Use of a check valve

In order to update the system, high investments are required. A big part of the stormwater system needs to be refurbished and if precipitation rates become higher a stormwater system of pipes and

22 CHAPTER 3. RESULTS Flood Risk Guayaquil canals on it self might not be able to accommodate the high precipitation rates.

3.6.1.6 Permeable paving In Guayaquil, almost every road and parking lot is paved with asphalt or concrete. As a result, streets have a fast runoff and no precipitation will infiltrate into the soil. If pavement would be more permeable, water infiltrates easier into the soil. Thereby, water has a lower flow rate within the soil and the soil might act as a temporary basin to avoid high peaks. This will decrease the stress on the stormwater system, since not all precipitation will reach the stormwater system. At the moment, several options are possible for permeable paving: parking lots, sidewalks and even roads. Note that on higher slopes these measures will not be as effective as in flat regions.

Figure 3.6.4: Example of permeable asphalt Figure 3.6.5: Example of green tiles [TARMAC, 2016] [Grass Concrete Ltd., 2016]

3.6.2 Measures considering flood defence In the following section different measures considering flood defence are proposed and evaluated to decrease the severity of floods in the city. In section 2.2 it became clear that flooding are mainly caused due to high water levels in the sea branches.

3.6.2.1 Levees at sea branches Considering the model outcomes discussed in section 3.3.1, it is known that in the sea branches a rather high tidal ampliﬁcation is present. Thereby, several sea branches were closed and land was reclaimed in the past. Nowadays, it is important to preserve the natural state of the sea branches as much as possible. Preserving the sea branches is favorable for drainage and also has aesthetic value for the city’s image.

The current problems ask for various solutions. A combination of gates with the construction of levees is suggested. At first, the idea of the barriers is elaborated. A gate should prevent extreme high water levels within the city (see figure 3.6.6). These barriers will close at low tide when a high tidal amplitude or severe precipitation is expected. Closure of the gates will create more storage area to drain water to the sea branches. The water quality will hardly be influenced due to the infrequent closing of the gate.

A closed barrier by itself will not completely stop the tide from penetrating into the city. Water could enter the city via low lying mangrove areas. Therefore, levees around the city should be

23 CHAPTER 3. RESULTS Flood Risk Guayaquil

Figure 3.6.6: Position of levees and barriers [Google, 2016a] implemented as well (see figure 3.6.6). This could be achieved by temporary levees or fixed levees. Which ones to use depends on social impact, costs and human welfare of the adjacent area. Temporary levees will be preferred for ecology and in densely populated areas where little space is available. However, these temporary levees are prone to vandalism in poor areas. In that case, fixed levees might be preferred. The municipality will start a small pilot project in the near future where they will test a barrier in one of the smaller sea branches. This pilot might prove if this measure will be suitable for all sea branches within the city (J.A. Ramirez Ponce, personal communication, 2016).

3.6.2.2 Levees at the Guayas river Protecting the city against the rising water levels in the Guayas river could be solved by constructing levees. Levees require hardly any maintenance compared to a barrier. Although levees are relatively cheap, there are some downsides. At the moment, there are hardly any levees present adjacent to

24 CHAPTER 3. RESULTS Flood Risk Guayaquil the Guayas river. Some people need to be relocated for the construction of levees. Furthermore, levees will result in a disruption of the current sight, especially within the city.

3.6.2.3 Dredging To decrease the water levels in the rivers dredging could be considered. When dredging of the rivers is studied a distinction has to be made between areas in the river that are affected by the tide and parts which are not influenced by the tide. As described in section 3.1.1.7, the estuary is tide dominated and the tide reaches up to 120 km upstream. The non tidal influenced areas are further elaborated on in appendix E.2. With help of section 3.1.1.11, the results of possible dredging in tide influenced areas can be predicted. Both horizontal and vertical dredging lead to an increased average flow depth in the estuary. This enhances a flood dominant character of the estuary (it enhances the imbalance between friction and convergence length, see section 3.1.1.11) and therefore increases the tidal amplification. Furthermore, the increased flood dominant character will cause intensified sediment import which counteracts the dredging works.

The desired eﬀects of dredging could be: (1) The increased navigability of the river. For this, vertical dredging can be a shortterm solution. However, this is neither a durable nor a sustainable operation. (2) Dredging could increase the accommodation space for runoﬀ by extreme precipitation rates or high river discharges. However, it is important to highlight that this will only have an effect during low tide, because the increased accommodation space will be overruled during high tide.

So, dredging the tide-influenced part of the river will only decrease the flood risk of the city during low tide or when tidal influences in the river are reduced in some way. Therefore, dredging will not be a suitable measure within the scope.

3.6.2.4 Barrier In order to reduce water levels and salt intrusion within the river Guayas a barrier could be constructed. In this part, two possible locations for barriers are suggested. Thereby, several pros and cons are elaborated.

Figure 3.6.7: Possible barrier locations in the Figure 3.6.8: Possible location of barrier 2 river Guayas [Google, 2016b] [Google, 2016b]

25 CHAPTER 3. RESULTS Flood Risk Guayaquil

Barrier at location 1 The first proposed barrier has practically the same location as proposed by cispdr. This barrier is positioned at location 1 in figure 3.6.7. An outlet must be present to drain river discharges frequently. cispdr proposed a barrier with gates that will close after low tide and will open when high tide has passed (see figure F.2). In figure 3.6.9, it can be seen what the effect of the barrier will be on water levels at Guayaquil. The linear increase of the water level is due to accommodation of river discharges upstream of the barrier. After high tide, gates will open when water levels on both sides coincide. So, the water drains with the tide.

Figure 3.6.9: Modelled time series at Guayaquil using a discharge with a return period of 100 years

Barrier at location 2 The barrier is situated further downstream, at location 2 in ﬁgure 3.6.7. More accommodation space for drainage from the city on the river is created. This location is preferable since navigation will not be hampered and a fair amount of discharge can continuously drain from the system.

Figure 3.6.10: Modelled time series at Guayaquil using a discharge with a return period of 200 years

Tide enters the system from left to right, as can be seen in appendix 2.3. Therefore, the tidal wave enters channel 1 (see figure 3.6.8). The barrier will partly reflect the incoming tide from channel 1 to channel 2. The water level gradient in channel 2 counteracts the tidal wave entering channel 4. Since channel 3 is significantly smaller than the main channel, friction might be important to

26 CHAPTER 3. RESULTS Flood Risk Guayaquil reduce the tidal amplitude. This leads to lower water levels at Guayaquil compared to a situation without a barrier. Only when really high discharges are present within the river Guayas gates are needed to drain discharges, since channel 3 has a limited capacity. In ﬁgure 3.6.10, the result is shown when high discharges are present during spring tide. This will lead to a situation where gates are only used in extreme situations. Monitoring of channel 3 will be important, since sedimentation within this channel should be avoided to maintain the same conveyance area.

General eﬀects due to barriers • According to the model, implementing a closure of the Guayas river leads to slightly higher water levels in the sea branch south west of the city. In appendix B.2, the model result is given for the inﬂuence of the barrier on the water levels in the sea branches.

• Salt intrusion is signiﬁcantly reduced. Although this cannot be modelled in a 2D model, reducing the tidal amplitude results in a reduced salt wedge [Pietrzak, 2016].

• Sediment transport will change near the barrier and therefore the introduction of a barrier may change the ecosystem. Note that there still is a tidal cycle present within the river.

• Without a lock in the barrier navigation is not possible for the barrier at location 1. However considering option 2, navigation is still possible through channel 3 but dredging might be needed to control the navigation depth.

• A barrier might lead to more ebb dominance, since flood flow is largely blocked by the barrier and ebb flow will remain present. This might decrease sediment import or could even enhance the sediment to be transported seawards.

• Closing of the gates must be executed slowly to prevent high pressure on the structure. The model results of rapid closing gates are present in ﬁgure B.2 in appendix B.2.

3.6.2.5 Bypass Lowering the water level in the river Guayas may be solved by implementing an additional channel (see figure 3.6.12). The discharge in the main channel is then divided over two channels and therefore the water level might drop in the Guayas river. However, tidal influence could dimish the effect of the bypass.

Problems may arise on the long term considering a permanent bypass. Sedimentation in the Guayas river might take place parallel to the bypass. In figure 3.6.11, the initial and long term effects of the bypass are shown. Besides, siltation problems at the inlet might occur due to for example gravitational pull and the Bulle effect [E., 2014]. Sedimentation at the main channel can be overcome by a weir at the entrance of the bypass. In this case, the bypass will only be used during flood conditions. This can be designed as a combination of a regular bypass and a floodplain. Due to the high tidal influence in the current system it should be further investigated if a temporary bypass will have the desired effect. An example of a temporary bypass is given in appendix E.6.

27 CHAPTER 3. RESULTS Flood Risk Guayaquil

Figure 3.6.11: Eﬀect on the main channel Figure 3.6.12: Potential location of a bypass [Drawing by E. Mosselman, in Havinga, 2014] [Google, 2016b]

3.6.3 Evaluation Each measure has his own characteristics. In order to have a good overview a simple Multicriteria- analyse (MCA) has been made. The measures are tested with the following criteria: problem solving, costs and social impact (see table 3.6.1). The measures compared to each other can be observed in ﬁgure 3.6.13, where the short and long term solutions are separated.

Problem Societal Long term or solving Costs impact short term Storage areas in the city +++ ++ ++ Short term Rooftops storage +++ ++++ +++ Short term Sea branches as storage +++ +++ ++++ Short term Check valves + ++++ ++++ Short term Permeable paving ++ ++++ +++ Short term Levees at sea branches ++++ ++ +++ Short term Levees at Guayas river +++ ++ +++ Long term Dredging + ++ ++++ Long term Barrier in Guayas river +++ ++++ Long term Bypass + + ++ Long term

Table 3.6.1: Evaluation/Summary table of possible measures

Short term Long term

Figure 3.6.13: Side channel eﬀects further downstream

28 4 Discussion

This study analyzes the ﬂood risk within Guayaquil. A thorough analysis has been made and several measures are proposed.

Part of the study was to evaluate the societal risk of Guayaquil. Since there was no time to ﬁnd data on assets within the city, we recommend a validation of societal risk using these assets. Design requirements calculated within this report are solely useful as an indication. A distinction is made between more and less vital structures within the stormwater system. Rough return periods are determined for corresponding discharges, precipitation and water levels. This is determined considering reference projects, the economic condition of Ecuador and interviews. Keep in mind that the method used to determine the required return period is rather subjective. The advised return periods are low compared to well developed countries. Within Guayaquil structures are designed with low return periods. Large improvements on return periods might lead to high investment and therefore might make policy makers cautious. On the other hand, it must be argued whether it is convenient to build large structures designed for a rather low return period.

The data series used to compute the water level corresponding to a return period of 200 years was somewhat short. Interagua recorded water levels since 2009. Those time series do not contain extreme weather events as happened in 1982-1983 and 1997-1998. Therefore, results might be too low. The return periods for water levels are determined by means of the current situation excluding sea level rise. However, a map has been given to show which areas will be aﬀected when sea level rises.

Diﬀerent scenarios have been modelled within Delft3D-FM. Since water levels at the river Guayas depend on multiple discharge boundary and no covariance is known between those boundary conditions, it was not possible to create a discharge within the Guayas river with a return period of 200 years. Therefore, both discharge boundaries are chosen with a return period of 200 years to simulate very high discharges. Moreover, the obtained discharges are a logarithmic extrapolation from values within the report of cispdr. We recommend to make a new probabilistic analysis with better correlations and data. The Delft3D-FM model has been used to show relative changes within the system due to sea level rise and river discharges. Possible eﬀects on water levels due to future measures are elaborated. These outcomes are all relative to the normal conditions of the same model. Absolute water levels are not presented, since the model shows deviations to measured data.

On short notice, it is advised that measures should be taken on the improvement of the stormwater system and on ﬂood defence in the southern part of Guayaquil. Minor adjustments could already be introduced within the system, whereas an overall improvement would be a large investment and operation. Those measures could be considered as long term solutions. The municipality is currently designing new measures for an improved system. The proposed measures within this

29 CHAPTER 4. DISCUSSION Flood Risk Guayaquil report should be revised when their design is complete. Note that treated drainage problems are mainly based on interviews and observations. Our result suggests (using a rough calculation) that storage basins within the city are possible. However, zoning and land-use regulations have not been considered. Besides, assets on proposed areas are not considered. A storage area within the city will always be a trade-oﬀ between the eﬀects and the losses.

Measures which result in lower water levels in the Guayas river are desirable on the long term. In chapter 5.1, three measures which reduce the probability of ﬂoods on the long term are presented. However, levees might increase consequences if they fail. Two locations for a barrier are proposed in this report. Both options perform well considering lowering water levels. Although a barrier at location 2 has more advantages (navigability, more accommodation space and constant drainage of discharge), it is not possible to label this barrier as the best option. It is a highly theoretical idea to oppose tide with tide (section 3.6.2.4). In addition, we recommend to model changes in sedimentation patterns near the barrier (including channels around the barrier) and within the Guayas river. If results happen to be unacceptable for the Guayas river, this solution should be revised. In addition, we propose a study on salt intrusion, which has not been analyzed extensively within the short term solutions. It is arguable if a barrier with gates is a proper measure for salt intrusion and high tidal amplitudes. To cope with both problems, the gates should be closed when extreme water levels are present. This will put high stress on the mechanical components of the barrier. Especially when elements fail, there is hardly any time to repair the barrier. Constructing and maintaining a barrier will be more expensive than constructing and maintaining a stretch of levees to protect the city. However, one might be more eﬃcient than the other. Be aware that solutions for the Guayas river are not advised at the moment.

To review the actual feasibility of all options, not only the eﬀectiveness of the measure should be studied, but the expenses as well. Costs are important for proper decision making. We recommend an extra study on feasibility so decision can be made on possible measures.

Dredging is considered to be a proper solution within the system according to some local institutions. However, this study shows that dredging might be ineffective on the long term within the area of tidal influence. Significant dredging within the tidal influenced area might even lead to a more flood dominant system, allowing more sediment to come into the estuary.

One of the considerations within this report was a permanent bypass. In such a bypass, sedimentation will take place on the long term, which is not favourable for the river Guayas. A bypass, which only opens during high water could be suitable though. If there will be more factors in favour of a bypass it is recommended to do a in-depth study on bypasses.

Most proposed measures will decrease the probability of floods and therefore the total risk of inundations at Guayaquil. Within this study, some research is executed on reducing the consequences of a flood. Relocating people, as carried out by the government, would be possible to reduce consequences of a flood for example. Furthermore, adaptive building (section E.5) is a measure on reducing consequences. Permeable paving is the most promising solution for reducing consequences. It is relatively easy to implement and cheap.

In appendix F, articles which initiated questions for the report are reviewed. Both articles were not within the scope of the report. Hallegatte et al. (2013) researched the vulnerability for natural hazards of 136 cities on a large scale. Therefore, ﬁndings from this report are not one-to-one

30 CHAPTER 4. DISCUSSION Flood Risk Guayaquil comparable. Guayaquil is ranked relative to other cities. Therefore, a rise or fall on the rankings may not be due to an increase or decrease of flood risk. In addition, cispdr developed a master plan for the entire country. For Guayaquil, they introduced a barrier in the river Guayas in combination with floodplains. Specific volumes for floodplains are not proposed, whereby a validation of the proposition is hard. Suggestions are given on the barrier concept. However, within this report it is explicitly stated that a barrier will not solve current issues. Policy To achieve a proper flood defence not only designs for physical measures should be composed. As can be seen in figure A.2, floods are often interregional or even interprovincial in Ecuador. Therefore, a strategy on a nationwide level considering flood defences might be useful. Controlling this on a national level could enhance the cooperation between municipalities and provinces. As shown in section 3.4, relations between the stakeholders must improve. This implies cooperation and comprehension of all parties. Several interviews revealed that improvements might be possible between the responsible parties. Our preliminary result shows complications between stakeholders. We recommend an extra study on political issues and legislation. Since knowledge about political mechanisms is not sufficient, an comprehensive solution is unfortunately not present within this report. Nevertheless, a good start would be a mutual understanding on the exact nature of the problems and responsibilities considering floods in Guayaquil by all involved parties.

5 Conclusions and recommendations

5.1 Conclusions The societal risk of floods in Guayaquil will increase in the near future. Due to sea level rise floods become more likely to happen adjacent to the sea branches. Nowadays, areas along the sea branches are flooded when high tide is present. More severe weather conditions may cause floods within the city due to the lack of a proper stormwater system. Several parts of the city are subject to different natural hazards, making an integral solution on reducing probabilities of failure necessary. To have a consistent approach on reviewing problems and measures a framework is proposed. Within this framework it should be possible to determine the severity of the problem, what kind of risk is assessed (e.g. human, economic or ecologic risk) and on what timescale it will take place. By this framework, the goal of the measures should be clearly defined. This will lead to a more consistent and uniform approach for researchers and policy makers to design measures. Often, main focus is on creating a ’nice’ solution without knowing the exact nature of the problem. This report shows that current problems ask for different solutions then for future problems.

Dredging is considered to be a proper solution within the system according to some local institutions. However, we suggest that dredging will be ineffective on the long term within the area of tidal influence regarding flood safety. Significant dredging within the tidal influenced area might even lead to a more flood dominant system, allowing more sediment to come into the estuary.

We also conclude that measures regarding high water levels within the Guayas river will not solve current problems within the system. So a barrier or levees within the Guayas river will not reduce current problems and thereby current risk.

5.1.1 Required measures On a short term, the city should be protected against ﬂooding caused by precipitation. Improve- ment of the stormwater system should be achieved. This includes proper runoﬀ in combination with storage areas and other smaller enhancements (see section 3.6.1).

Supplementarily, high tides cause ﬂooding within the southern part of Guayaquil. Constructing levees along the sea branches with gates at the inlets, as presented in section 3.6.2.1, should increase ﬂood safety within this area. Both measures should be executed on a short term.

5.1.2 Future measures If sea level rise will continue or the severity of weather conditions will increase, measures on lowering the water levels in the Guayas river are required. From all proposed solutions in chapter 3.6, the

33 CHAPTER 5. CONCLUSIONS AND RECOMMENDATIONS Flood Risk Guayaquil ones that are most feasible are stated below:

• Levees at the river Guayas (section 3.6.2.2)

• Barrier downstream of Guayaquil (section 3.6.2.4)

• Barrier further downstream of Guayaquil (section 3.6.2.4)

5.2 Recommendations First of all, it is advised that measures should be taken for improvement of the stormwater system and for ﬂood defence in the southern part of Guayaquil. It is advised to introduce already the following minor adjustments in the system on a short term:

• Installing check valves and pumpingstations on drainage outlets.

• Implementing permeable pavement during road maintenance and construction.

• Using gutters and temporary storage at houses.

Due to a lack of time, skills and provided data many assumptions and simpliﬁcations have been made. Therefore, more extensive studies should be executed. Below recommendations are given for becoming more precise by further research:

• A thorough analysis on economical acceptable return periods to design measures.

• An analysis and comparison on the societal consequences of ﬂoods and measures.

• Better calibration of the Delft3D-FM model of Guayaquil to research absolute eﬀects of the proposed measures.

• New statistic calculation on weather conditions.

• The cost vs. beneﬁt of all proposed measures should be determined.

• Consider societal changes due to implementing storage areas within Guayaquil.

• Constructing a framework for decision making on ﬂood defences.

• Changing strategies and possibly regulations to increase incentives for improving ﬂood defences.

34 Bibliography

[Aerts et al., 2008] Aerts, J. C., Botzen, W., Veen, A., Krywkow, J., and Werners, S. (2008). Dealing with uncertainty in ﬂood management through diversiﬁcation. Ecology and Society, 13(1):1–17.

[Arriaga, 1989] Arriaga, L. (1989). The Daule-Peripa Dam Project UrbannDevelopment of Guayaquil and their Impact on Shrimp Mariculture.

[Barrera Crespo, 2016] Barrera Crespo, P. (2016). Delft3D Flexible Mesh modelling of the Guayas river and Estuary system of Ecuador.

[Cai et al., 2014] Cai, W., Borlace, S., Lengaigne, M., van Rensch, P., Collins, M., Vecchi, G., Timmermann, A., Santoso, A., McPhaden, M., Wu, L., England, M., Wang, G., Guilyardi, E., and Jin, F.-F. (2014). Increasing frequency of extreme El Ni˜noevents due to greenhouse warming.

[Castro, 2009] Castro, B. (2009). Sedimentation processes at the conﬂuence of the Daule and Babahoyo rivers, Guayaquil, Ecuador. El Palmar island.

[Cherry Mortgages, 2016] Cherry Mortgages (2016). Flood, earthquake and tsunami restistant housing. http://www.cherrymortgages.com/sustainable_zero_carbon_housing/flood_ earthquake_and_tsunami_resistant_housing.htm. 12-09-2016.

[Draftlogic, 2016] Draftlogic (2016). Google maps area calculator tool. https://www.daftlogic. com/projects-google-maps-area-calculator-tool.htm. 03-10-2016.

[Drawing by E. Mosselman, in Havinga, 2014] Drawing by E. Mosselman, in Havinga (2014). Projects on Rhine branches in the Netherlands [PowerPoint slides]. https://blackboard. tudelft.nl/bbcswebdav/pid-2573549-dt-content-rid-8642391_2/courses/36516- 151602/CIE5311_04_2014_1D_Projects_Rhine_branches_NL_weinig_RVR.pdf.

[Dutchwatersector, 2013] Dutchwatersector (2013). Boskalis contracted for dutch room for the river project at veessen-wapenveld, the netherlands. http://www.dutchwatersector.com/news- events/news/6663-boskalis-contracted-for-dutch-room-for-the-river-project-at- veessen-wapenveld-the-netherlands.html. 19-10-2016.

[E., 2014] E., M. (2014). River bifurcations, part 1 [PowerPoint slides]. https://blackboard. tudelft.nl/bbcswebdav/pid-2573549-dt-content-rid-8642396_2/courses/36516- 151602/CIE5311_05b_2014_River_bifurcations_Part_1.pdf.

[emapag-ep - Interagua, 2016] emapag-ep - Interagua (2016). Plan de Manejo de Aguas Lluvias en la Cuenca Noroeste de Guayaquil.

35 BIBLIOGRAPHY Flood Risk Guayaquil

[ESPOL, 2016] ESPOL (2016). Visi´ony misi´on. http://www.espol.edu.ec/es/nosotros/ vision-y-mision. 16-09-2016.

[Google, 2016a] Google (2016a). Google maps. https://www.google.com.ec/maps/place/ Guayaquil/@-2.6457586,-79.8899702,9z/data=!4m5!3m4!1s0x902d13cbe855805f: 0x8015a492f4fca473!8m2!3d-2.1709979!4d-79.9223592. 12-09-2016.

[Google, 2016b] Google (2016b). Google maps. https://www.google.nl/maps/place/ Guayaquil,+Ecuador/@-2.225314,-79.8971669,64142m/data=!3m1!1e3!4m5!3m4! 1s0x902d13cbe855805f:0x8015a492f4fca473!8m2!3d-2.1709979!4d-79.9223592. 15- 10-2016.

[Grass Concrete Ltd., 2016] Grass Concrete Ltd. (2016). Car parking with sustainable grass reinforcement. http://specificationproductupdate.com/2016/08/12/grass-concreteltd- grass-permeable-paving/. 24-10-2016.

[Hallegatte et al., 2013] Hallegatte, S., Green, C., Nicholls, R., and Corfee-Morlot, J. (2013). Fu- ture ﬂood losses in major coastal cities.

[Hallegatte et al., 2011] Hallegatte, S., Ranger, N., Mestre, O., Dumas, P., Corfee-Morlot, J., Her- weijer, C., and Wood, R. (2011). Assessing climate change impacts, sea level rise and storm surge risk in port cities: A case study on Copenhagen.

[Hollis, 1975] Hollis, G. (1975). The effect of urbanization on floods of different recurrence interval. Water Resources Research, 11(3):431–435.

[iha, 2016] iha (2016). Changjiang institute of survey, planning, design and research. https://www.hydropower.org/companies/changjiang-institute-of-survey-planning- design-and-research. 16-09-2016.

[INAMHI, 2012] INAMHI (2012). E. Anuarios hidrol´ogicos1984-2012.

[INAMHI, 2016] INAMHI (2016). La institution. http://www.serviciometeorologico.gob. ec/la-institucion/. 16-09-2016.

[INOCAR, 2016] INOCAR (2016). Precipitation en guayaquil. http://www.inocar.mil.ec/web/ index.php/precipitacion-en-guayaquil. March 2013, site invoked: 16-09-2016.

[Ioualalen et al., 2014] Ioualalen, M., Montfret, T., B´ethoux,N., Chlieh, M., Ponce Adams, G., Collot, J., Martillo Bustamante, C., Chunga, K., Navarette, E., Montenegro, G., and So- lis Gordilla, G. (2014). Tsunami mapping in the Gulf of Guayaquil, Ecuador, due to local seismicity.

[IPCC, 2013] IPCC (2013). Climate change 2013: the physical science basis contribution of working group I to ﬁfth assessment report of the intergovernmental panel on climate change. Chapter summary for policymakers. Cambridge University Press.

[Jimenez and Matamoros, 2009] Jimenez, D. and Matamoros, D. (2009). Modelaje De Un Sistema Urbano De Alcantarillado Pluvial En El Area´ De Drenaje De Los Esteros Miraﬂores Y Represado, Ciudad De Guayaquil.

36 BIBLIOGRAPHY Flood Risk Guayaquil

[Jonkman et al., 2016] Jonkman, S., Steenbergen, R., Morales-N´apoles, O., Vrouwenvelder, A., and Vrijling, J. (2016). Probabilistic Design: Risk and Reliability Analysis in Civil Engineering. Course reader, CIE4130.

[Miller, 2009] Miller, K. (2009). Land under Siege: Recent Variations in Sea Level through the Americas. Working paper.

[Mobile Geographics, 2016] Mobile Geographics (2016). Guayaquil, ecuador tide chart. http: //tides.mobilegeographics.com/locations/2324.html?y=2016&m=9&d=9. 12-09-2016.

[Pietrzak, 2015] Pietrzak, J. (2015). An Introduction to Physical Oceanography for Civil and Oﬀshore Egineers. Course reader, CIE5317.

[Pietrzak, 2016] Pietrzak, J. (2016). An Introduction to Stratiﬁed Flows for Civil and Oﬀshore Egineers. Course reader, CIE5302.

[Saavedra Mera et al., 2014] Saavedra Mera, J., Larrea, G., Loor, H., Castillo, R., Fortis, R., Mar- cillo, P., Vera, H., Cor´azar,M., Mar´ın,L., Rivas, K., Granja, R., Cires, J., Hidrobo, I., and Barreiro, P. (2014). 25 Presa Daule - Peripa a˜nos1988-2013. CORPORACION´ ELECTRICA´ DEL ECUADOR HIDRONACION.

[Savenije, 2006] Savenije, H. (2006). Salinity and tides in alluvial estuaries. Elsevier.

[Secretaria del Agua, 2014] Secretaria del Agua (2014). Ley organica de recursos hidricos, usos y aprovechamiento del agua, no 39/2014. http://www.asambleanacional.gob.ec/es/contenido/ley-organica-de-recursos- hidricos-usos-y-aprovechamiento.

[senagua, 2016] senagua (2016). La secretar´ıa. http://www.agua.gob.ec/category/la- secretaria/. 16-09-2016.

[Stive and Bosboom, 2015] Stive, M. and Bosboom, J. (2015). Coastal Dynamics I. VSSD.

[SuárezChanguán,2010] SuárezChanguán,P. (2010). Muelle de Servicio Isla Santay. Estudios y Diseños. http://simce.ambiente.gob.ec/sites/default/files/documentos/anny/ Informe%20Final%20Muelle%20de%20Servicio%20Isla%20Santay%20Estudios%20y%20Dise% C3%B1os_0.pdf.

[TARMAC, 2016] TARMAC (2016). Topmix permeable. http://www.tarmac.com/solutions/ readymix/topmix-permeable/. 24-10-2016.

[sgr, 2016] sgr (2016). La secretar´ıa. http://www.gestionderiesgos.gob.ec/la- secretariadsdfwefsef/. 16-09-2016.

[Twin2Go, 2016] Twin2Go (2016). Guayas river basin fact sheet. http://www.twin2go.uos.de/ images/stories/CaseStudies/twin2go_fact_sheet_guayas%20.pdf. 15-09-2016.

[Uzochukwu et al., 2009] Uzochukwu, G., Schimmel, K., Chang, S., Kabadi, V., Luster-Teasley, S., Reddy, G., and Nzewi, E. (2009). Proceedings of the 2007 National Conference on Environmental Science and Technology.

[Warrick and Oerlemans, 1990] Warrick, R. and Oerlemans, J. (1990). Sea Level Rise.

37 BIBLIOGRAPHY Flood Risk Guayaquil

[Wyrtki, 1977] Wyrtki, K. (1977). Sea level during the 1972 El Ni˜no.

[Xinqiang et al., 2015] Xinqiang, N., Qigui, Y., Zhiyu, Z., Yan, H., Xiaojun, Z., Xiangyang, H., Jianghe, H., Hongzhong, X., Gaohong, X., Ni, F., Xuejun, X., Zhaoming, X., Gaohong, X., Tienv, G., Xiao, Z., Shengyi, G., Kexu, F., Jun, S., Sirong, Z., Liming, Z., Xiaojie, M. Jun, S., Zhengxiang, W., Xintian, Z., Sirong, Z., Zheng, G., and Xin, L. (2015). Plan Hidráulicoregional de la demarcaciónhidrografáficaGuayas.

38 A System analysis

A.1 Observations site visits

On September 9th 2016 (3:15 pm) the authors made their ﬁrst ﬁeld observations on revetments and water levels within the city of Guayaquil. The water level during high tide this day was 3,10+mlw at 12:59 pm and the water level during low tide was 0.67+mlw at 7:55 pm. By means of a simple sinus function with a M2 tide (12,42 hours) the water level at the time of the observations was approximated to be 2.40 m. Figure A.1.1 indicates this is a fair estimation.

Figure A.1.1: Tide during observation [Mobile Geographics, 2016]

The observations are shown in figure A.1.2. From the observations it can be concluded that at the western side of the Guayas river the defence of the city against floods is not uniform and changes approximately every 30 meters. It seems that protection of the river banks is not the responsibility of one party. In fact, it seems that the river bank is protected locally or that when there is a problem it has been fixed very locally. This results in some less protected areas. In addition, the river banks revetment are sometimes damaged or flushed away (see figure A.1.2c ). This indicates that these banks are or were not able to withstand the force of the water. Moreover, from the observations one might notice that many river banks do not reach more than 1.5 meters above water level during the periods the observations where made. For now the river banks are assumed to be at a water level of 3.90+mlw. On Isla Santay, which is an island in the Guayas river, no artificial river bank protection is present because it is a nature reserve. As can be seen in figure A.1.2d the unprotected riverbanks are subjected to erosion. From this it might be concluded that river bank protection is needed to prevent erosion in this region. In earlier days these banks were covered with mangroves.

During the second site visit, 2-10-2016 (5:00 p.), the water level was at ebb spring tide. Some

39 APPENDIX A. SYSTEM ANALYSIS Flood Risk Guayaquil

(a) (b)

Figure A.1.2: Field observations 09-09-2016

drainage pipes were now visible which were not seen in the ﬁrst site visit, see ﬁgure A.1.3. This means that these pipes are under water during higher tides and are not able to drain the water to the river during that time. However, it could also be pumping pipes or old drainage pipes which are not used any more.

Figure A.1.3: Field observations 2-10-2016

40 APPENDIX A. SYSTEM ANALYSIS Flood Risk Guayaquil

A.2 Elevation Guayaquil

Figure A.1: Elevation of Guayaquil provided by Interagua 41 APPENDIX A. SYSTEM ANALYSIS Flood Risk Guayaquil

A.3 Earthquakes and Tsunamis

The coast of Ecuador has very fragmented and complex bottom. The northern region of Ecuador and the southern region of Colombia generate powerful tsunamigenic earthquakes due to subduc- tion of the Nazca plate and the central zone of Ecuador is characterized by moderate seismicity.

In 2014, a research paper from M. Ioualalen et al. was published about the potential tsunamis present in the Gulf of Guayaquil due to local seismicity. A numerical model was used for the seismicity prediction and another model was used for the propagation of waves (fully nonlinear and dispersive). It is possible that a slide of a plate will be present in the Gulf of Guayaquil. However, this will not lead to a tsunami in the gulf because the vertical movement of the sea ﬂoor is absent. The expected magnitudes are not signiﬁcant and a tsunami is not assumed to amplify, because it is generated at shallow water, compared to deep water earthquakes. The most powerful modelled earthquake has a probability of occurrence of 1 in 500 years, which seems reasonable because larger return periods are never observed in the history.

In the same research it is stated that distant tsunamis generated outside the Gulf of Guayaquil tend not to generate significant flooding in the Gulf of Guayaquil. Although few small tsunamis have occurred in the past, there is no record of significant tsunami impact on the coastal zone of Guayaquil due to distant earthquakes. Although an earthquake would not lead to a tsunami with significant floods it might be important to design future measures which can resist earthquakes, especially since a combination of a failure of measures cannot be combined with potential (although not enormous) high water levels due to tsunamis [Ioualalen et al., 2014].

A.4 Wind

Records of long and short periods have indicated that the predominant wind direction is Southwest with a maximum wind speed of 8.0 m/s, as shown in figure A.1 [SuárezChanguán, 2010]. This is negligible compared to other factors within the system.

Figure A.1: Wind direction and speed [Su´arezChangu´an,2010]

42 APPENDIX A. SYSTEM ANALYSIS Flood Risk Guayaquil

A.5 Stormwater system

Figure A.1: Stormwater system in Guayaquil provided with Interagua

43 APPENDIX A. SYSTEM ANALYSIS Flood Risk Guayaquil

A.6 The El Niñophenomenon Trade winds blow across the Pacific Ocean from East to West at the height of the equator and are part of the Hadley circulation. Next to these trade winds there is an additional circulation called the Walker circulation, which is driven by the East - West temperature gradient. The wind creates a pressure gradient with a set up in the West, and a set down in the East Pacific. With the absence of Coriolis near the equator a simple balance is present. The walker circulation enhances the effect of cool water in the East and warm water in the West.

When the intensity of the trade winds reduces the temperature gradient drops. The system tries to reach a new equilibrium, the pressure gradient reduces which means that the set down in the east decreases. This phenomenon is called the El Niñophenomenon. As mentioned earlier, the Walker circulation enhances the Trade Winds. However, during an El Niñophenomenon the circulation weakens the winds. An El Niñophenomenon is recognized when the pressure drops near Tahiti for a sufficient long period [Pietrzak, 2015]. An illustration of the El Niñophenomenon is given in figure A.1.

Figure A.1: Cartoon of the El Ni˜nophenomenon

An El Niñophenomenon can have global impact. Under normal conditions warm air rises above the western Pacific and precipitates at the middle of the Pacific Ocean, annually between 3 tot 5 meters. During an El Niñophenomenon two circulations are present. The warm air rises in the middle of the Pacific and precipitates partly above parts of Latin America. These increased precipitation rates during the wet season cause severe inundations. Besides, the pressure gradient drops and the water temperature rises resulting in increased water levels near the coast of Ecuador. Sea level rise due to an El Niñophenomenon can be divided into 5 stages.

1. Built up of the sea level in the western Paciﬁc

2. Trade winds reduce in power causing the sea level to drop in the west and rise in the East

3. A rapid drop of sea level in the West ﬁlling up the Paciﬁc trough

4. A second peak of sea level rise in the East

5. At last the water level equalizes very quickly

44 APPENDIX A. SYSTEM ANALYSIS Flood Risk Guayaquil

A.6.1 Large historical inundations

Figure A.2: Eﬀected zones by El Ni˜nophenomenon 1982-1983 [Xinqiang et al., 2015]

45 APPENDIX A. SYSTEM ANALYSIS Flood Risk Guayaquil

Figure A.3: Eﬀected zones by El Ni˜nophenomenon 1997-1998 [Xinqiang et al., 2015]

46 APPENDIX A. SYSTEM ANALYSIS Flood Risk Guayaquil

A.7 Sedimentation The estuary is subject to several sedimentation related concerns. There are a few important reasons why sedimentation occurs and why this might cause problems.

• Deforestation of mangroves leads to instability of the estuary banks and thereby higher sediment availability in the system.

• The funnel shaped estuary of Guayaquil creates a convergence of tidal energy and therefore causes the tidal amplitude to increase landwards. Contrarily, friction causes the energy to decline. In this case bed friction is overruled by convergence energy due to width restriction. Naturally the system tries to restore the balance between convergence and friction. Restoring the balance can be obtained when the water level of the estuary near Guayaquil decreases, in other words sedimentation will occur [Barrera Crespo, 2016].

• Typically, rivers with high discharges are wide and uniform in width. Due to the decreased discharge by construction of the The Daule-Peripa Dam (see section 3.1.1.1) the river Daule get more converged. The increased convergence leads to a lower transport process and sedimentation takes place. [Savenije, 2006].

• The expansion of shrimp farms and other aqua cultural activities leads to less inter tidal areas in the estuary. The reduction these inter tidal areas cause for an increase of the average channel depth. This leads to less friction and enhances a ﬂood dominant tidal character. The natural balance between convergences and friction will further disrupt and causes sedimentation in order to restore it.

B Model outcomes

B.1 GIS modelling

The city of Guayaquil is small enough to use a projected coordinate system. The wgs84 ellipsoid is used to model the Earth in the Universal Transverse Mercator (utm) coordinate system. The earth is divided in 60 zones which each have a width of 6 degrees. Furthermore, a division is made between location North and South to the equator. In order to project the city of Guayaquil on a map the following model is used: wgs 1984 utm Zone 17s.

The data provided by Interagua contained a Guayaquil.tif file which indicates the elevation with respect to msl. With the help of the raster calculator tool all levels below 3,5 m msl are indicated, these are called polygons. In order to be flooded these polygons need to be hydraulically connected to the river or the sea branches. All the polygons which are not connected are eliminated in the model. In order to estimate the flooded area within the city of Guayaquil a distinction is made between rural and urban areas. This results in the distinction between rural and urban floods. An error is created in the polygon adjacent to the river. The polygon was partly situated in urban and partly situated in rural area and therefore need to be separated manually, which obviously results in computation errors. Furthermore, some of the polygons are partially located in the river or sea branches resulting in an overestimation of flooded area within the city.

B.2 Modelling barrier

For simplicity, gates within the barrier are modelled as a time dependent weir. When gates are open, the weir is at the bottom of the water column. When closing the gate, the weir is gradually increasing in height till a height is reached which is signiﬁcantly higher than the water level.

Influence of a barrier on water levels in the seabranch In figure B.1, the consequences of the barrier in the Guayas river on the water level in the sea branch can be seen. From the figure one might concluded that the elevation of the tide due to the barrier is negligible.

Barrier at location 2 with mean wet season discharge In ﬁgure B.2, the situation of a barrier is given during spring tide, with mean wet season discharge. Rapidly closing gates lead to fast changes in water levels and thereby high loads on the barrier. The diﬀerences in water levels on both sides of the gate can be seen by means of the troughs just after closure.

49 APPENDIX B. MODEL OUTCOMES Flood Risk Guayaquil

Figure B.1: Inﬂuence of dam on water level in sea branch

Figure B.2: Water levels at Guayaquil

50 APPENDIX B. MODEL OUTCOMES Flood Risk Guayaquil

B.3 Tidal Propagation

Figure B.1: Tidal current velocity over a tidal cycle (1) [Barrera Crespo, 2016]

Figure B.2: Tidal current velocity over a tidal cycle (2) [Barrera Crespo, 2016]

C Stakeholder analysis

In this section the indicated stakeholders are elaborated on.

C.0.1 Government of Ecuador The Government of Ecuador is responsible for the safety of its inhabitants and the community at national scale. They provide rules and regulations by means of risk assessment, safety standards and site planning. Within this study two ministries and more local governmental institutions are considered.

Secretaria del Agua (SENAGUA) The Ecuadorian ministry of water is called senagua and its main goal is to gain permanent access to ’clean’ water and to make proper use of the exploitation of water resources. senagua is responsible for the control and distribution of water from reservoirs over rural areas [senagua, 2016]. In section 3.1.1.1, it is mentioned that the discharge regulation by the dam in the Daule river causes sedimentation near Guayaquil. Furthermore, senagua is partly responsible for risk aversion considering inundations. senagua was, until 2014, responsible for irrigation, drainage and dredging in the country. However, the provincial governments got this attribution [Secretaria del Agua, 2014].

Secretaria de Gestion de Riesgos (SGR) The main goal of the Risk Management Ministry is stated as follows: ”Ensuring the protection of persons and communities from the negative eﬀects of both natural and human induced disasters.” [sgr, 2016]. Furthermore, the ministry aims to incorporate risk management in all levels of public and private institutions by generating policies, strategies and standards that promote identiﬁcation, analysis, prevention and mitigation of risk. sgr controls the national risk center and provides information about natural hazards.

Prefecture of the Guayas Province The province is an autonomous government with a political, administrative and ﬁnancial autonomy. Parallel to the provincial government the executive power of the president is represented in the province by a governor. The province encompasses an area of approximately 17 km2 with 4.1 million inhabitants of which 3.8 million live in the city of Guayaquil. The provincial area covers almost the complete Guayas estuary, the Daule, Babahoyo and Vinces rivers and a large part of their catchment areas. The prefecture is responsible to preserve the water quality and hydrodynamic conditions of the river (J.A. Ramirez Ponce, personal communication, 2016). By national law, public services considering drainage and irrigation are established in national planning by senagua. However, the planning and execution is the responsibility of the autonomous decentralized provincial governments in accordance with their respective powers [Secretaria del Agua, 2014].

53 APPENDIX C. STAKEHOLDER ANALYSIS Flood Risk Guayaquil

Municipality of Guayaquil The municipality of Guayaquil represents the people of Guayaquil and is elected by them. The mayor is individually elected by the inhabitants and has the supervision and responsibility of the municipality. The municipality and mayor of Guayaquil are the direct responsible for ﬂood mitigation and relief in the city. The mayor, accompanied by the municipality, submits proposals to the ministries in order to get funds for ﬂood defence (P. Cornejo-Grunauer, personal communication, 2016). Furthermore, the municipality is accountable for sewage, stormwater system and water supply. EMAPAG emapag is a public company governed by the municipality of Guayaquil to provide the city with sewage, a stormwater system and drinking water supply. emapag is responsible for long term visions and strategies for the municipality considering water resources. This is done in collaboration with Interagua. emapag is the link between the Municipality and Interagua (J.A. Ramirez Ponce, personal communication, 2016).

C.0.2 Interagua Since 1999, the water services have been privatized. The company Interagua (ruled by Veolia) is the operator and is responsible for the development of the system. Interagua is responsible for drinking water, sewage and the stormwater system in Guayaquil. The latter has a big inﬂuence on ﬂoods in and around Guayaquil. Interagua is in charge of information about precipitation levels, discharges through the current storm sewers and are responsible for the construction and maintenance of all structures.

C.0.3 Inhabitants Inhabitants have a big influence on the development of the city. Indirectly, they decide which actions are made regarding flood protection. A significant part of the people would like to have direct solutions for visible problems, for example traffic jams. Floods are considered to be less important, because they are not a day-to-day problem and therefore easily forgotten (P. Cornejo- Grunauer, personal communication, 2016).

C.0.4 The Escuela Superior Polit´ecniadel Litoral (ESPOL) espol is an institution of higher education specialized in scientiﬁc and technical education located in Guayaquil. It is within the class A, the highest academic category in the country. espol wants to be a leader and international benchmark for higher education. Their mission is to form excellent professionals in the studies they provide. They are able to provide information about the region of the project. espol could provide experts for academical and research purposes [ESPOL, 2016]. Furthermore, the research executed at this academic institution may create a basis for policy makers.

C.0.5 Instituto Oceanogr´aﬁcode la Armada (INOCAR) The basic functions of inocar are providing security for marine navigation, research in oceanography, compile the national nautical map. In addition, it represents the country in international organizations in relation with hydro-oceanic activities. Their mission is to plan, coordinate and control the technical and administrative activities related to: Hydrographic Service, Navigation, Oceanography, Meteorology, Marine Sciences, Marine signaling and Management of Specialized Equipment Activity. They have information about the waterways, water-and sediment streams and seabed in the area of study.

54 APPENDIX C. STAKEHOLDER ANALYSIS Flood Risk Guayaquil

C.0.6 Instituto Nacional de Meteorologia e Hydrologia (INAMHI) inamhi is the national meteorological institute of Ecuador. It has the capacity and obligation to provide vital information on weather, climate and water resources. inamhi is an institution with national and international representation and is member of the World Meteorological organization, wmo [INAMHI, 2016]. inamhi has the ability to monitor and predict the behavior of the atmo- sphere and inland waters. In addition, the institute produces early warning systems that can save lives, reduce property damage and protect the environment in case of hazardous event. Moreover, it operates and maintains the infrastructure of national meteorological and hydrological stations. inamhi strives to contribute to national prevention and protection concerning natural disasters. C.0.7 Changjiang Institute of Survey, Planning, Design and Research (CISPDR) cispdr is a state owned high-tech enterprise and an international contractor certiﬁed by the Min- istry of Commerce of China [iha, 2016]. In the past, the contractor the completed survey, planning and design of the Three Gorges project. Furthermore, cispdr is involved in the South-to-North Diversion Project in China.

In 2012 cispdr was assigned to make a hydraulic analysis of Ecuador at large [Xinqiang et al., 2015]. In the report published in 2015 they provided several solutions for the current problems in the Daule, Babahoyo and the Vinces river. With these solutions peak discharges could be controlled and might prevent ﬂoods according to the institute. Their strategy to prevent Guayaquil and its surroundings from ﬂoods is thoroughly evaluated in section F.2.

D Design conditions

D.1 Probability of exceedance For the determination of the design parameters for the flood protection measures the return period of the different discharge, water levels and precipitation levels have to be met. From the different interviews it came to notice that it is common to talk in terms of return periods instead of probabilities and design life. The relation between the three mentioned values is given in equation D.1 [Jonkman et al., 2016]. 1 P (x > X) = 1 − (1 − )y (D.1) n With P (x > X) = probability of exceedance [%]; n = return period[y]; y = design life [y]

From [Xinqiang et al., 2015] it can be concluded that it is desirable to design for a load (being a water level, extreme discharge or precipitation level) with a return period of 200 years. For the two other design requirements a small list of reference projects is made. However, not all data in the table originates from a scientiﬁc source and therefore the values are only assumed to be a robust estimation. The results are shown in table D.1.1.

return period [y] design life [y] Pexceed [%] Cost [million usd] Thames Barrier 2.000 50 2.5 760 Maeslant Barrier 10.000 100 1.0 530 Eastern scheldt Barrier 4.000 200 4.9 8.700 St. Petersburg Barrier 10.000 100 1.0 840 Afsluitdijk 4.000 100 2.5 *1.000 Alsluitdijk(redesign) 10.000 50 0.5 850 *Current value. Table D.1.1: Reference projects storm surge barriers

Furthermore, an analysis is made on probabilities of exceedance corresponding to set return periods and design lives given in table D.1.2. A distinction is made between the functional requirements for big structures like barriers and smaller, less costly and less vital structures like drainage pipes. It is decided to determine the design life of a large barrier or dike by means of reference projects. From the table a design life of 100 years and a return period of 200 years as proposed earlier results in a probability of exceedance of almost 40%. Therefore, it should be highlighted that the design parameters for precipitation, water level and discharge have a risk of almost 40% to be exceeded over the design life time of 100 years.

Although, the shorter design life of smaller structures causes the probability of exceedance of the design parameters to decrease this probability is still high. Furthermore, due to the lack of data,

57 APPENDIX D. DESIGN CONDITIONS Flood Risk Guayaquil

Return Design Pexceed Design Pexceed Design Pexceed Design Pexceed period [y] life [y] [%] life [y] [%] life [y] [%] life [y] [%] 5 100 100 40 100 30 99.8 10 86.5 10 100 100 40 98.2 30 95 10 63.2 50 100 86.5 40 55.1 30 45.1 10 18.1 100 100 63.3 40 33.0 30 25.9 10 9.5 200 100 39.3 40 78.1 30 13.9 10 4.9 500 100 18.1 40 7.7 30 5.8 10 2 1000 100 9.5 40 3.9 30 3 10 1 10000 100 1 40 0.4 30 0.3 10 0.1

Table D.1.2: Probability of Exceedance for diﬀerent design lives and return periods it will not be possible to determine all wanted design parameters for a 200 year return period. Therefore, also smaller return periods are considered and the resulting design requirements are given in table D.1.3.

return period [y] design life [y] Pexceed [%] (Storm surge) Barrier 200 100 39.3 Large components 200 30 13.9 Medium components 100 30 25.9 Small components 50 30 45.1

Table D.1.3: Design requirements for diﬀerent components in a ﬂood defence system

D.1.1 Design water level In order to determine the design water level at the site, the data which was provided by Interagua is used. The provided measurements are obtained at a station in Guayaquil in the river Guayas. The data is registered between 30-08-09 and 13-11-09 with a sampling interval of 5 minutes and has a height relative to msl. From 07-12-09 to 28-09-16 the water levels are observed with a sampling interval of 15 minutes.The dataset is given in figure D.1. The dataset seems to be a significant, but there are some important notes. At first, the station occasionally registered only one observation a day. The station was probably not adjusted in the right manner at that time. Second, the time series need to have an uniform sampling interval in order to be of use. In addition, there are many observations that reach water levels which are much lower than a realistic tidal amplitude could be. These observations will be disregarded in order to have a good approximation of the design water level. In the graph two high peaks can be observed. These peaks are caused by a hardware error at the station of Guayaquil, which measured the water level higher than it should be. For this reason these observations are not considered.

The adjustments mentioned lead to 7 years of measurements with 254189 observations. These are shown in figure D.2. Although 7 years of data is not much, due to lack of more data this will probably provide the best estimation of the required design water level. In order to find the design water level for the given return period a Peak over Threshold method (PoT-analysis) is used. In this analysis, the highest water level per tide should be taken into account. In total 3625 observations are found with a threshold higher than 2 meter. The PoT-data is plotted by means of a Gumbel distribution which can be seen in figure D.3.

58 APPENDIX D. DESIGN CONDITIONS Flood Risk Guayaquil

Figure D.1: Water levels Guayaquil in river Guayas

Figure D.2: Filtered water levels Guayaquil in river Guayas

With the use of the regression line of this ﬁgure it is possible to calculate the water level for the return period Q of 200 years. The average number of observations above 2 meter per year ’Ns’ is 3625 ( 7,1 =)511, 6 and the probability of exceedance of a storm in a year Qs = N s ∗ Q. By means of formula D.2 the design water level can be determined.

59 APPENDIX D. DESIGN CONDITIONS Flood Risk Guayaquil

Figure D.3: The Gumbel exceedance graph of water level

Ns 511, 6 h = γ − β ln(ln( ) = 2, 19 − 0.17 ln(ln( )) = 3, 07m (D.2) Ns − Qs 511, 6 − 511, 6 ∗ 1/200

The design water level with a return period 1 in 200 years is msl+ 3,07 m. To conclude this calculation it is highlighted that within the used data set only one moderate El Niñophenomenon(2009) is registered. If the dataset would contain more or more severe El Niñophenomena the design water level would increase. D.2 Design discharge cispdr made an analysis on discharges corresponding to four return periods at different cities in the Guayas region. The discharges with a certain return period at the cities St. Lucia and Samborondónare given in table D.2.1.

Return period [years] 10 25 50 100 Discharge St. Lucia [m3/s] 2.200 2.770 3.090 3.520 Discharge Samborond´on [m3/s] 4.420 5.000 5.430 5.850

Table D.2.1: Discharges at diﬀerent return periods [Xinqiang et al., 2015]

The needed design river discharge has a return period of 200 years. In order to achieve this, the data in table D.2.1 is logarithmic extrapolated (see figure D.1). This results in a discharge of 200 years of 3.904 m3/s in the Daule river (at St. Lucia) and 6.286 m3/s in the Babahoyo (at Samborondón). D.3 Design precipitation For the approximation of the precipitation in Guayaquil data of inamhi is used. To determine the frequency curve, the maximum annual records in 24 hours of precipitation are taken [emapag-ep - Interagua, 2016]. By emapag-ep-Interagua, the methodology of Gumbel’s extreme value analysis is used in order to get the maximum values of precipitation in 24 hours for different return periods which can be seen in table D.3.1.

For the analysis of design precipitation also a return period of 200 years is desirable. By means of a logarithmic extrapolation of the data in table D.3.1, the related value of 263,5 mm per day is found (see ﬁgure D.1). Note that the above mentioned amount is not bound to a interval of 24 hours but could also fall in a shorter period of time.

60 APPENDIX D. DESIGN CONDITIONS Flood Risk Guayaquil

Figure D.1: Frequency curve discharge

Return period [years] 2 5 10 25 50 100 Precipitation [mm] 93.5 132.1 151.7 186.4 214.3 237.5

Table D.3.1: Return period of 24 hours storm [emapag-ep - Interagua, 2016]

Figure D.1: Frequency curve precipitation

From the diﬀerent return periods a Intensity-Duration-Frequency (idf) analysis is done by Interagua and is presented in ﬁgure D.2 . Unfortunately, the idf curve with a return period of 200 years has not been elaborated. Thereby the required data to determine with a return period of 200 years curve is not available for this research.

61 APPENDIX D. DESIGN CONDITIONS Flood Risk Guayaquil

Figure D.2: idf analysis [emapag-ep - Interagua, 2016]

62 E Possible measures

This appendix contains in depth information which further elaborates on the theories and statements made in section 3.6.

E.1 Storage Areas

The total area of Guayaquil according to Google Maps is 344.5 km2. However, the western part is mostly not paved and therefore not considered as city area. The total area considered can be seen in ﬁgure E.1 and is approximately 220 km2.

Figure E.1: Considered city area [Draftlogic, 2016]

The storage has to withstand a precipitation with a return period of 200 years, which is equal to 263,5 mm per day. Because high precipitation rates often coincide with higher water levels in the river and the sea branches due to for example the El Ni˜nophenomenon. Therefore, it is assumed that all the runoﬀ ends up in the storage areas.

In order to get an idea of the size of these storage areas a rough calculation is made. The total volume of water is equal to 220.000.000 · 0.2635 = 57.970.000 m3. The total storage area in the city is approximately 7.100.000 m2, this would result in 8 meter deep reservoirs. Combining this solution with the storage in the sea branches the depth could decrease. This depends on the water level in the sea branches. It would be desirable if the storage basins

63 APPENDIX E. POSSIBLE MEASURES Flood Risk Guayaquil could be emptied in the river under gravitational force.

In reality not all the drainage water would end up in the storage area. An in depth study should determine how much storage area is required. The stormwater system would probably fail during an extreme event before the storage areas will be filled. E.2 Dredging In non tide-influenced areas dredging could lead to other results than mentioned in section 3.6.2.3. Dredging increases the cross-sectional profile to accommodate higher discharges and therefore reduce water levels. However, due to the current high sedimentation rates in the river the dredged parts might not retain their increased depths for a long time. Therefore, dredging will probably not provide a sustainable solution against flood risk on its own. To predict the exact possibilities on dredging more comprehensive studies have to be executed. The non tide-influenced areas are further upstream so it is not within the scope of this project. E.3 Babahoyo dam The Daule-Peripa dam regulates the discharges in the Daule river. Construction of a dam in the Babahoyo and Vinces rivers could completely regulate the discharge of the Guayas river throughout the year. During wet season discharges could be decreased and in the dry season water could be drained. The construction of these dams can further decrease salt intrusion.

Dams in the Vinces and the Babahoyo river could prevent inundations downstream. A reduced discharge can cause the water level to drop near Guayaquil even with tidal inﬂuence. It is also important to note that till the Andes, the slope is very small in the Babahoyo river.

The dam could be used to produce energy and for irrigation purposes. However, it is very expensive. Furthermore the dam has a big inﬂuence on the ecosystem.

E.4 Maeslantbarrier A similar kind of barrier as the Maeslantkering could be constructed in the Guayas river. The barrier can be closed when extreme high water levels near the city are predicted. The advantage of such a barrier is that the discharge is not hindered when the barrier is open. The barrier can not operate every tidal cycle tidal. Closing the barrier would simply take too long, especially due to the large width of the river. Thereby, compared to the Netherlands, storm surge is not present within Guayaquil. E.5 Adapted buildings Instead of protecting against floods, adaption can be a solution as well. An interesting solution could be construction of more high rise buildings. Only the ground floor will be affected during a flood. Thereby, it is a efficient way of land use.

Floating buildings can be seen as adaption as well. These could be constructed both on land as in the water for instance. When the city ﬂoods the buildings simply rise simultaneous with the water level.

64 APPENDIX E. POSSIBLE MEASURES Flood Risk Guayaquil

Figure E.1: Floating house [Cherry Mortgages, 2016]

Both solutions will require a lot of investments and are only feasible for the long term. When no hard measures are taken floods might occur even more than nowadays. During flood conditions a large part of the city could malfunction. E.6 Bypass An example of a bypass that is only used during flood conditions is the high water channel at Veessen-Wapenveld in the Netherlands. The high water channel is constructed as a part of the Room for the river project. The project should protect the surrounding areas against extreme events. The 8 km long and 500 to 1500m wide channel is able to lower the water level in the current river by 71 cm. The channel is not dug out, but two dikes are constructed to enclose the river. Furthermore, bridges are build and recreational and ecological sites are realised. The total cost of the project is estimated at 75 million Euro (approximately 82 million usd). The flood planes will be used as agricultural lands during normal conditions. A schematising of the bypass is given in figure E.2 and an artist impression of the inlet is illustrated in E.1.

Figure E.1: Inlet of the high wa- Figure E.2: Overview of the high ter channel Veessen-Wapenveld water channel Veessen-Wapenveld [Dutchwatersector, 2013] [Dutchwatersector, 2013]

F Article reviews

In the following appendix the articles that led to this research will be elaborated on. The articles provided solutions for the current en future problems in Guayaquil. F.1 Hallegatte et al.: Future flood losses in major coastal cities The Nature Climate Change published a letter of Hallegatte et al. in 2013. In this letter they provide a quantification of present and future flood losses in the largest coastal cities around the world. Note that this is an economical research and not a hydraulic research. The method used for determining flood risks is divided into five steps. Step one, a statistical analysis of past storm surges in cities. Second, a geographical analysis of the population and exposed assets. Followed by an assessment of direct economic losses in case of storm surge. The fourth step is an assessment of indirect losses; production, job losses and reconstruction duration. And lastly, a risk analysis of the effectiveness of coastal flood protections is executed, including risk changes due to climate change and sea level rise [Hallegatte et al., 2011, p.114]. Afterwards, the probability of flood levels is derived using three simple models for failure. Furthermore, different socioeconomic scenarios combined with six scenarios of environmental change, changing subsidence and sea level rise led to 108 different combinations.

Of course, this study is simplified since it is a global research. This simplification can give wrong results, especially when assumptions taken at developed cities are copied to cities in developing countries. For example, due to lacking data in some cities assets are evaluated considering insured assets. Insured assets in developed countries could be roughly equal to the total value of assets, where in developing countries this can be totally different. By not knowing details of the study concerning Guayaquil, it is hard to rely on the outcome of this article, since the ranking is relative to other cities. So a different ranking in 2050 could be caused by changes in the Guayaquil safety standards or by changing standards in other cities.

Hurricanes are within the calculation for the average annual loss. Guayaquil is indicated as prone to hurricanes or tropical cyclones, which can be questionable. Since hurricanes are not present within the Guayaquil basin. However, the El Ni˜nophenomenon can produce severe weather conditions that may be comparable to hurricanes without wind gusts.

The high ranking of Guayaquil potentially creates fear and awareness in the city.

67 APPENDIX F. ARTICLE REVIEWS Flood Risk Guayaquil

Figure F.1: Part of 20 cities with highest loss in 2050, assuming sea level rise of 20 cm and maintaining ﬂood probability [Hallegatte et al., 2013]

F.2 CISPDR: Planiﬁcaci´onde control de inundaciones

In December 2015 the Chinese Research institute cispdr made a plan to prevent inundations in the Guayas Province. The plan starts with a brief recap of all previous ﬂood events. Furthermore, a model and data analysis were made to come up with several solutions. The Babahoyo, the Vinces, the Daule and the Bulubulu river form the basin of the river Guayas.

Figure F.1: Basin area of Guayas river [Twin2Go, 2016]

Near the Bulubulu river several adaptions were already implemented before cispdr published their report. The construction of these plans was shortly mentioned in their report and are quite similar to the ones cispdr came up with for the Babahoyo, Vinces and Daule river.

68 APPENDIX F. ARTICLE REVIEWS Flood Risk Guayaquil

F.2.1 Solutions Babahoyo river As can be observed in figure F.1, the catchment area of the Babahoyo river stretches over a wide area and contains several mountains. These mountains cause flood waves to travel with high speed and increase in size rapidly. Inundations in the Babahoyo river are the result of flood waves in combination with a small capacity of the lower lying parts of the river. At this moment the Baba- hoyo river has a discharge capacity of approximately 1420 m3/s. According to cispdr this has to increase till 3840 m3/s during high peak discharges. cispdr came up with 5 alternatives to overcome this problem.

1. Construct levees and dredge the river.

2. Construction of 4 reservoirs upstream of the Calope, Suquibi, Sibimbe and Pita rivers. These reservoirs cover an area of 2590 km2.

3. A combination of alternative 1 and 2.

4. Alternative 3 in combination with an additional storage for ﬂood waves.

5. Construct Alternative 4 together with a bypass that leads high discharges peaks directly to the mouth of the Guayas. Upstream the bypass is connected to the Juntas river.

In the report these 5 alternatives are elaborated and the last one is recommended as best measure. The main reason to implement this series of solutions is that otherwise possible levees would need to be designed with a level of 9 meters, this causes big impact on the landscape. The total capacity of the system has to be 3840 m3/s. The discharge is determined with help of inhabitants and the desirable return period for a certain area. The bypass would take 200 m3/s, the reservoirs have to accommodate 1390 m3/s in total, the heightening of the levees creates an capacity of 1780 m3/s in the river and the additional storage has to store 470 m3/s.

F.2.2 Solutions Vinces river The river Vinces crosses the city of Vinces which is the most important place to protect. Similar alternatives as the Babahoyo river where initiated except last solution with bypass. The current capacity of the river Vinces is 750 m3/s, according to the solutions of cispdr this has to increase till 2750 m3/s. Alternative 4 which includes a storm storage, 3 reservoirs, dredging and increasing levee height was chosen to be the most promising one. The 3 reservoirs reduce/regulate the discharge more downstream. In total these 3 reservoirs have a catchment area which covers 2590 km2. The reason for the solution is the same as for the Babahoyo river, the high levees disrupt the landscape especially near the city of Vinces.

F.2.3 Solutions Daule river In contradiction to the previous two main rivers that mouth in the Guayas, the Daule river already has a major reservoir. The functions of the Daule-Peripa Dam can be revised at section 3.1.1.1. The dam can withstand a ﬂood that occurs once every 50 years, which is equal to 3380 m3/s of 4210 m3/s when the power generation is cut oﬀ. Despite these high discharges, the river near the city of Daule has a current capacity of 1680 m3/s. The current capacity upstream as well as downstream has to be improved with the help of levees, next to that the capacity of the reservoir will be increased to accommodate storage in case of peak discharges.

69 APPENDIX F. ARTICLE REVIEWS Flood Risk Guayaquil

F.2.4 Guayas River Barrier cispdr proposed a solution for each river basin of the Guayas individually. Complimentary a adjustable barrier is designed south of Guayaquil. The location of the dam is given by number 1 in ﬁgure 3.6.7. The main purpose of this dam is to prevent high tide to propagate into the Guayas at the height of Guayaquil. Furthermore it decreases the salt intrusion, which causes major problems for drinking water treatment purposes and irrigation nowadays. The dam has to close every tidal cycle for approximately 3 to 4 hours and could therefore be prone to failure. The dam closes right after low tide and opens again when high tide has passed, as can be observed in ﬁgure F.2.

Figure F.2: Closure of barrier proposed by cispdr [Xinqiang et al., 2015]

F.3 Dredging

From the report it is not clear where the exact areas are that are to be dredged, nor is the amount of dredged material or the approximated dredging depth. However, for each river the length to be dredged are mentioned. ”In the Babahoyo river a canal with a length of 150km needs to be dredged. Furthermore, in the river Vinces and the river Guayas 110km and 60km need to be dredged respectively. In other tributaries another 310km needs to be dredged making the total works 630km.” As the report does not clearly states where the exact locations of dredging are and with what purpose the dredging works are hard to evaluate. However, from section E.2 it can be considered that the interventions for the non tide-influenced parts are a possibility to decrease the flood risk of the adjacent areas although not very sustainable. The 60km that is planned to be dredged in the river Guayas is probably for a large part tide-influenced. If this intervention is made to create accommodation space it might not be a sustainable solution because of the arguments mentioned in section 3.6.2.3.

F.4 Eﬀects and consequences of measures

In the following section the proposed solutions will be discussed. Both positive and negative consequences will be given.

F.4.1 Bypasses As discussed in section 3.6.2.5 can the water level be lowered by implementing a bypass and therefore ﬂoods can be reduced. In ﬁgure 3.6.11 it is shown that the main channel will sedimentate in the long term, which is not preferable. Of course, these returning sedimentation problems can be solved by maintenance dredging.

70 APPENDIX F. ARTICLE REVIEWS Flood Risk Guayaquil

F.4.2 Reservoirs Reservoirs can temporarily store water and regulate the discharge of the river and therefore can ﬂatten out peak discharges. The regulation can be helpful regarding exploitation of water during the dry season. In both the Babahoyo and the Vinces river cispdr proposed to build several reservoirs and in the Daule river a reservoir is situated already.

Although a reservoir has several advantages it also has disadvantages. Knowing that the rivers contain a lot of sediment, sedimentation in the reservoir might need a lot maintenance. Either the dam has to contain a ﬂush system or dredgers have to be available. More regulation of discharges cause even more sedimentation near the conﬂuence of the Daule and Babahoyo river and Guayas estuary as can be found in section 3.1.1.11. Especially on the long term sedimentation can cause severe problems. Furthermore, the design of the reservoirs and additional storage by cispdr is somewhat unclear. No sizes or locations for the basins are given. The capacity of the reservoir is solely given in terms of a discharge (m3/s) that needs to be accommodated without any insight in for what period of time this discharge continues. Therefore the volume (m3) of the basins can not be calculated.

F.4.3 Additional flood basin Both for the Babahoyo and the Vinces river an additional flood basin is proposed. The flood basin for the river Guayas will be situated above the E484 and the E25 on the west side. This area is partly in its natural state, the rest is covered with meadows or plantations. This area will be preferred because hardly any crops are lost when the basin floods. However a lot of people would be affected by this temporary flood basin. Especially at the northern side of the N484 more houses can be found. cispdr has determined that the return period will be less than 25 years. It is unclear how the chosen area will contain the water and how adjecent areas are protected against flood. The high ways are not constructed on higher ground and can therefore not form the levees which should surround the basin. Also secondary issues are not discussed for example, are the inhabitants in the area of the additional basin warned and financially supported in case the basin is used? How will the basin be drained? And what are the influences of sediment on the agricultural areas after the basin is used?

F.4.4 Dam Babahoyo river A dam within the Babahoyo river can regulate the discharge within the river, just as the Daule Perida dam does. When both rivers can be regulated, peak discharges can be potentially avoided. However, since the Babahoyo river has a very mild slope, a dam must be placed far upstream, close to the mountains. This means that peak discharges can still occur, during high precipitation. Therefore a dam within the Babahoyo river will not be considered as a proper solution.

F.4.5 Barrier The proposed barrier will reduce salt intrusion significantly. If executed as their report stated, it will reduce water levels in the river Guayas as well, according to figure 3.6.9. The mechanical operation of gates on a daily basis might be prone to hazardous situations. When parts malfunction, little time is present for repairing, since during the next tidal cycle the gates must be closed again. Especially during severe weather events this can lead to large problems for the city. Furthermore, the report states an water level set up of 20-60 cm on the sea side of the barrier when this is closed. Effects on the adjacent areas should be studied and further elaborated.

71 APPENDIX F. ARTICLE REVIEWS Flood Risk Guayaquil

F.5 Discussion The Chinese institute delivered a report concerning a national plan for, among other things, water safety in the country. Several measures are proposed within our scope.

The proposed barrier could be a good solution especially for salt intrusion. However, a solution specific for protecting Guayaquil against floods is not included. This report can be misleading for policy makers, since as far as this research goes, it is not explicitly stated that several extra measures are needed to protect Guayaquil from floods: Sea branches should be defended, since many floods occur there at the moment and drainage within Guayaquil must be improved since most floods occur in the city during high precipitation. As mentioned in section 3.6.2.5, sedimentation might occur at the entrance of bypasses. Keeping all sedimentation problems in mind, dredging might be needed. This kind of concerns are not stated within the report. As well as locations for storage reservoirs are not mentioned, which is important to know to map the social and economical impact. Lastly, some small remarks can be made on missing information. In the report little can be found about expectations for sea level rise due to both climate change and the El Niñophenomenon and how this is included in the proposed solutions.

Overall, the report gives some good solutions for the Prefecture of the Guayas Province, but the eﬀect can be questionable. Without extra measures, like maintenance dredging and improving drainage same problems might still occur. Placing an expensive barrier without extra measures, proposed in section 3.6, will not lead to favourable outcomes concerning ﬂoods, but will reduce salt intrusion. However, it can be argued if that will be worth the expenses.