flood mitigation case study

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• Published: 01 June 2023

GIS-based hydrodynamic modeling for urban flood mitigation in fast-growing regions: a case study of Erbil, Kurdistan Region of Iraq

• Andam Mustafa 1 ,
• Michał Szydłowski 1 ,
• Mozafar Veysipanah 2 &
• Hasan Mohammed Hameed 3  

Scientific Reports volume  13 , Article number:  8935 ( 2023 ) Cite this article

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• Civil engineering
• Climate-change mitigation
• Environmental impact
• Natural hazards

Floods threaten urban infrastructure, especially in residential neighborhoods and fast-growing regions. Flood hydrodynamic modeling helps identify flood-prone locations and improve mitigation plans' resilience. Urban floods pose special issues due to changing land cover and a lack of raw data. Using a GIS-based modeling interface, input files for the hydrodynamic model were developed. The physical basin's properties were identified using soil map data, Land Use Land Cover (LULC) maps, and a Digital Elevation Model (DEM). So, the HEC-RAS 2-D hydrodynamic model was developed to estimate flood susceptibility and vulnerability in Erbil, Iraq. The case study examines the quality of flood modeling results using different DEM precisions. Faced with the difficulty, this study examines two building representation techniques: Building Block (BB) and Building Resistance (BR). The work presented here reveals that it is possible to apply the BR technique within the HEC-RAS 2-D to create urban flood models for regions that have a lack of data or poor data quality. Indeed, the findings confirmed that the inundated areas or areas where water accumulated in past rainfall events in Erbil are the same as those identified in the numerical simulations. The study's results indicate that the Erbil city is susceptible to flood hazards, especially in areas with low-lying topography and substantial precipitation. The study's conclusions can be utilized to plan and develop flood control structures, since it identified flood-prone areas of the city.

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Introduction.

Floods have developed into an event that people in developing countries regard as routine during the rainy season. Flash floods caused by climate change are one of the most common causes of fatalities and property damage in the twenty-first century. Recently, frequent urban flash floods have become the most popular topic among scientists, engineers, and local authorities in prone regions. Droughts and floods have historically been the most deadly natural disasters 1 . Aptly, the effects of flooding are expected to worsen as the world's population grows, the economy grows, and climate change 2 . Samanta, et al. 3 classified floods into three types: flash floods that last a few hours; floods that last several hours to several days; and floods that occur gradually over a relatively long period of time. Cities in general have become locations that are more prone to be flooded as a result of continued urbanization and population growth 4 . Therefore, even though these natural disasters were unavoidable, it is necessary to investigate flood hazards in order to better manage them going forward. Flood hazard assessment and modeling, in conjunction with inundation maps, can be of assistance to climate experts and scientists in this regard.

Building detailed flood inundation maps is typically done through the use of hydrodynamic models. A significant amount of data, time, and computational resources are required for the development of a hydrodynamic model for a large hydrological basin, all of which must be available at the same time 5 . In developing countries, obtaining archived data for rainfall-runoff modelling, high-resolution DEM for topography and accurate LULC for basin characteristics is a challenge. As Loudyi and Kantoush 6 pointed out, a serious challenge for flood risk assessment in the Middle East and North Africa (MENA) region is the unavailability and sometimes unreliability of data, particularly for the calibration and validation of flood models. There are some approaches that could be considered to fill such gaps, for example, as part of hydrological and hydrodynamic modeling of urban floods in Erbil, previously LULC from Landsat satellite images were prepared for the study area 7 . Furthermore, the availability of such data allows a more precise description of hydrological processes occurring in the real world, paving the way for a more numerical approximation of the processes involved in urban flooding. As a result of historical efforts to mitigate flood impacts, flood loss and damage in developed countries, particularly when measured in terms of the number of fatalities, is generally less severe than in developing countries 8 .

Researchers in many parts of the world have attempted to use geospatial techniques to model floods in urban and rural areas 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 for surface and ground water detection 17 , 18 , analyzing rainfall 19 , 20 , 21 , LULC analysis 22 , 23 , 24 , 25 , 26 , 27 , and finally flood risk mapping and analysis 28 , 29 , 30 , 31 , 32 . A model that utilizes artificial neural networks (ANN), geographic information systems (GIS), and remote sensing (RS) was developed by 33 , 34 to estimate ground water recharge mapping in the Iraqi Western Desert. Using a long-term perspective, a group of Polish researchers presented a method for analyzing the impact of urbanization on the frequency of flooding inside an urban catchment 35 . The integration of GIS remote sensing data and survey data with the ANN was used by 36 to generate a hydrological soil group map for Alghadaf Wadi in Iraq, providing timely, fast, and relatively cheap data for mapping and monitoring soil texture. Samela, et al. 14 developed a GIS tool that is able to delineate areas that are prone to flooding in an efficient and cost-effective manner. El-Saoud and Othman 37 estimated flash floods in Makkah's catchment region utilizing spatial parameter distribution and mathematical hydrological and hydrodynamic modelling. This study created a flash flood risk map. SZYDLOWSKI 38 presented flash flood propagation computations in natural and urban areas, shallow water equations are used to model free surface unsteady water flow. There are a variety of 2-D numerical models and software packages available, each with its own set of capabilities and developed by a variety of different developers; some must be purchased, while others are free and open-source 39 . Glenis, et al. 40 presented and validated City Catchment Analysis Tool – CityCAT, a novel software for modeling, analysis, and visualization of surface water flooding. It consists of a 2-D overland flow routing model that provides quick evaluation of combined pluvial and fluvial urban flood risk and the effects of various flood mitigation strategies. Macalalad, et al. 41 set up the Liuxihe model in order to develop a forecasting scheme and simulate the observed flood process. The study reproduced past flash flooding events and demonstrated a significant correlation between past dense storm events and their respective simulated river discharges. With the help of a 2-D rainfall-runoff simulation at the basin scale, Costabile, et al. 42 investigated the performance and capabilities of the HEC-RAS 2-D model. Mustafa and Szydłowski 43 demonstrated how different building representation techniques and hydrodynamic models can influence the results of urban flood simulations using the HEC-RAS 2-D package. Both BB and BR can be applied in HEC-RAS 2-D. Alipour, et al. 44 examined HEC-RAS 2-D's configuration factors and parameters. They investigated the effects of several model configuration factors, such as the floodplain and channel roughness coefficients, terrain and mesh size, and river boundary conditions, on the dynamics of water levels, maximum water level and flood extent.

Following the invasion of Iraq by the coalition forces in April 2003, Erbil, the capital of the Kurdistan Region of Iraq (KRI), became the focal point of development in the region and is now regarded as an important political, economic, and administrative center not only for Iraq but also for the neighboring countries 45 . KRI has taken steps to develop its oil and gas industry and attract investment from international oil companies since 2009, in order to increase its capacity and prepare for a gradual transition to independence 46 . Rapid urbanization is one of the main causes of flash floods in Erbil. As a result, the patterns of LULC in Erbil have changed significantly over the last two decades, particularly in the urban areas 7 . The most important factor that has a significant impact on creating the danger of flash flooding is the improper use of land for urbanization where the paths of the waterways have been closed. In the aftermath of this, the number of urban flash floods has also increased significantly 47 . Changes and developments to the land surface within cities will have an effect not only on the likelihood of increased flooding, but also on urban water management generally 48 . On the other hand, there have been studies that have linked the increasing frequency of floods to the impact of climate change 49 , 50 . For applications in urban settings, high temporal resolution of precipitation, such as sub-daily, is required for establishing a relationship between extreme precipitation Intensity–Duration–Frequency IDF 51 , 52 , 53 . When it comes to developing countries such as Iraq, the number and distribution of stations capable of recording rainfall on a shorter time scale are limited. The Indian Meteorological Department (IMD) equation was used to determine the rainfall data for periods shorter than 24 h, and IDF curves and empirical IDF formulas for the city of Erbil were developed as a result of these limitations 54 . To assess flood risk, scientists consider the likelihood and severity of a flood in a specific area at a specific time, along with the potential consequences 55 , 56 , 57 .

From 1950 to 2010, the number of people who died in Iraq as a result of flooding was only 11 1 . In the fourth quarter of 2021, Erbil was struck by flash floods on October 30 and December 17, the latter of which was particularly devastating, resulting in the deaths of 12 people and the disappearance of the body of a 10-month-old child for almost two months. Another flash flood hit Erbil on January 13, 2022, approximately one month after the previous one. Specifically, this one was located mainly within the study area that we modeled in HEC-RAS 2-D in this paper. Flash floods are more common in areas with a dry climate and impervious terrain because lack of pervious surface or vegetation allows torrential rains to flow overland rather than infiltrate into the ground. According to the available evidence, the city has experienced three floods in the span of just three months. According to a press release from the province of Erbil, more than 7000 people were declared to be in a state of special calamity 58 , and the total flood damage in Erbil was estimated to be $14,5 million 59 . The economic impact of recent flash floods has increased dramatically. Despite the devastation caused by Erbil's flash floods, the study area's summer fresh-water shortage makes flash floods a valuable source of water.

This paper addresses a critical issue of urban flash floods in Erbil and presents a new approach to model and identify flood-prone areas using HEC-RAS 2-D hydrodynamic model, where there has been no such work previously. The novelty of the work lies in discussing the challenges of accurately assessing and modeling flood hazards in this area, particularly regarding the availability and reliability of data. Previous studies on stormwater management in Erbil have been lacking, and there is a need to establish sustainable strategies to mitigate the adverse effects of flooding on the socio-economic fabric of society. The study highlights the importance of accurate topographic representation using a DEM of different precision to improve the flood modeling results. The impact of floods on society is also discussed, emphasizing the need for effective management strategies. This study is the first of its kind in the study area, and it is expected to provide valuable insights into developing sustainable urban stormwater management practices.

Materials and methods

Erbil (also known as Hawler in the Kurdish language) is the capital city of the Kurdistan Region in northern Iraq, and it is the region's largest city by population. Erbil, Iraq's second-largest city in the north of the country after Mosul, is the region's economic hub. In 2020, it was expected to have a population of 2,254,422 inhabitants and more than one million of them living in the city center. Erbil Province has a total land area of 14,873.68 km 2 2 , 60 . The investigation will be focused on the central district of Erbil. In the hydrodynamic modeling using HEC-RAS 2-D, the area that was considered was within the 120 m ring road (circular highway around the city), which is approximately 102.38 km 2 . Due to the fact that a DEM with an acceptable resolution is only available within this boundary, only this area is considered in the modeling as the study area in HEC-RAS 2-D (Fig.  1 ). In general, Erbil Province has a semi-arid continental climate, which is characterized by hot and dry summers and cold and wet winters, owing to its geographic location on the Arabian Plate. It is only possible to consider this climate for the city center because the mountainous region to the north and northeast of the province, which has a Mediterranean climate, cannot be considered. More detailed information can be found in 47 , 61 , 62 .

© ESRI, URL: https://www.esri.com/en-us/arcgis/products/index ).

Study area. Base imagery sources: Esri, DigitalGlobe, GeoEye, i-cubed, USDA FSA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community. These maps were processed and generated in ArcGIS 10.7 software (

Data availability and processing

In the development and simulation of hydrological and hydrodynamic models, the availability of raw data is the most important factor to be considered. It was necessary to acquire a DEM from the Shuttle Radar Topography Mission (SRTM) ( http://dwtkns.com/srtm30m/ ) with a resolution of one arc-second (30 m) in order to delineate the watershed boundary of the study area (Fig.  2 ). Li and Wong 63 conducted an analysis to determine how various DEM data sources may influence the outcomes of hydrologic applications. A DEM with a resolution of 10 m was created using the point clouds of the LIDAR images (the data source was the Erbil municipality, the work date back to 2010). Then, a Feature Manipulation Engine (FME) was used to generate another DEM over the study area, from the layout map of the city, the heights of the buildings were extracted to create a building layer in three dimensions (3D). From the buildings, a raster with spatial resolution of 1 m was created. After resampling the DEM of the city (only the area inside 120 m ring road) from 10 to 1 m, it was then overlaid on the raster accompanied by the buildings. Raster calculation with maximum operation was applied to create a DEM of the city with a resolution of 1 m (Fig.  3 ).

Delineation of watershed using a Digital Elevation Model (DEM) with a resolution of 30 m. This map is processed and generated in ArcGIS 10.7 software (

Digital Elevation Model (DEM) with 1 m resolution for modeling area (BB technique simulations) in HEC-RAS 2-D. This map is processed and generated in ArcGIS 10.7 software (

The Food and Agriculture Organization of the United Nations (FAO) prepared a digital soil map of Iraq, from which a soil map of the studied area was extracted. Brown soils with deep phases have dominated the soil profile in the area under consideration for 2-D hydrodynamic modeling (Fig.  4 ). The Natural Resource Conservation Service (NRCS) divided soils into four Hydrologic Soil Groups (HSG) based on their runoff potential 64 . A, B, C, and D are the four HSGs, where A has the least potential for runoff and D have the most. The study area for modelling in HEC-RAS 2-D is in group C 62 .

The soil classes in the study area. This map is processed and generated in ArcGIS 10.7 software (

The LULC map was created using data collected through remote sensing. When cloudy coverage is less than 5%, a satellite image from Sentinel-2B (2017–present) was downloaded from the Copernicus open access hub platform ( https://scihub.copernicus.eu/ ), which is operated by the European Space Agency. The image was captured by a satellite on September 13, 2021. Regarding the LULC classification, the study area was divided into three categories: built-up (which included residential, industrial, commercial, local streets, roads, and other urban areas); bare land (which included uncovered soils, unused areas, and dry river beds); and vegetation (including forests, orchards, vegetable fields, parks, lawns, shrubs, and others) (Fig.  5 ). Approximately 66.36 km 2 (64.82%) of the total study area is covered by built-up areas, while 25.038 km 2 (24.45%) and 10.97 km 2 (10.71%) respectively are covered by bare land and vegetated areas.

Land use land cover classes inside the modeling area in HEC-RAS 2-D. This map is processed and generated in ArcGIS 10.7 software (

HEC-RAS 2-D model setup

Water flow through natural rivers and other channels is modelled using HEC-RAS 6.1, an open-source software developed by the U.S. Army Corps of Engineers (USACE) to simulate hydrodynamics of water flow. One-dimensional 1-D steady and unsteady flow modeling, as well as two-dimensional (2-D) unsteady flow modeling, as well as combined one-dimensional and two-dimensional 1-D/2-D unsteady flow routing, sediment transport/mobile bed computations, and water temperature/water quality modeling are all possible with this software 65 , 66 . The Digital Terrain Model (DTM) is responsible for inducing the majority of the topographic characteristics of the study into the HEC RAS 2-D model. Using a DEM as an input file, HEC RAS 2-D is capable of creating a DTM within the program. Specifically, a DEM plus buildings with a resolution of 1 m was prepared for use in the generation of the study area's DTM in this case. In the geometric data editor of the software, a 2-D flow area describing the boundary of the assumed flood domain is created by drawing a polygon with the orthophoto as the background layer. Afterwards, an automatically generated computational mesh within the boundary layer is created with a 10 × 10 m cell size. This results in a total of 1,022,897 grid cells with an average size of 100 m 2 . To demonstrate the effects of computational cell size on the model outputs and model run time, two more mesh configurations with 8 × 8 and 20 × 20 m are examined. The total number of grid cells in these mesh configurations is 1,598,552 (average cell size = 64 m 2 ), and 255,501 (average cell size = 400 m 2 ), respectively. The four building representation techniques that are commonly used to model built-up area flooding in hydrodynamic numerical models are the BB, BR, Building Hole technique (BH), and Building Porosity technique (BP) 67 , 68 , 69 , 70 , 71 . In the HEC-RAS 2-D, both BB and BR are applicable. BB technique means increasing the ground elevation of building units by modifying distributed ground elevation data, by configuring the buildings to a real height or a sufficiently high artificial elevation value to ensure no water flows over the buildings. Here, the entire simulated flow area should be meshed as a unified grid, so water flows around buildings. In BR, the modeler may give each grid a different Manning coefficient. High Manning coefficients result in low water flow velocity. In this method, the simulated building areas are given a high Manning n value to increase friction. In other simulated areas, a low value represents the real land cover. Due to the high friction coefficient assigned to the building units, water flows slowly over them but behaves as if there is a high resistance against flow. A detailed description can be found in 43 .

The model's other parameters, which include 2-D surface roughness, curve number for LULC classes, boundary conditions, and rainfall data, are also required. Table 1 categorizes the LULC classes, Erbil City center is a densely urbanized area with predominant brown soil and deep phase. Thus, based on imperviousness and soil type, three different Manning's n are selected for the 2-D area 72 ; see Table 2 . Defining boundary conditions within the HEC RAS 2-D flow area is required in order to run the 2-D model simulations. Boundary conditions for defined 2-D flow areas can include a variety of features such as flow and stage hydrographs, normal depths, rating curves and precipitation boundary conditions, among other things. In the current study, only 23 outlets are defined as boundary conditions with normal depth. A time series of rainfall is used as meteorological data in the unsteady flow section for each storm event, and a simulation run is carried out to generate flood inundation for each storm event.

Analyzed long-term series of maximum daily rainfall data were used in this study and within them, a theoretical probability distribution of 10, 5, and 1%, which is equal to 71.16, 83.21, and 113.49 mm 47 (see Fig.  6 ). The method that was used to prepare the temporal rainfall distribution was based on Huff's second quartile 74 . The reasons for using this method are explained in 47 . Uniform rainfall distribution in space is considered. Unsteady flow routing can be done two-dimensionally with either the Shallow Water Equations (SWE) or the Diffusion Wave equations (DWE). To solve the flow over the computational mesh using HEC-RAS, three sets of equations are available: the Diffusion Wave equations; the Shallow Water Equations (SWE-ELM, or Shallow Water Equations, Eulerian–Lagrangian Method) original equations; and a more momentum-conserving Shallow Water Equations solution (SWE-EM, which stands for Shallow Water Equations, Eulerian Method) 66 . In the present study, the original (SWE-ELM) was considered for HEC-RAS 2-D. The flowchart shown in Fig.  7 illustrates the process of developing a HEC-RAS 2-D model.

Temporal distribution of rainfall for three probability distributions of 10, 5, and 1%.

A flowchart illustrating the steps involved in developing a HEC-RAS 2-D model.

Results and discussion

Analysis of different mesh resolutions and building representation techniques.

This study compared two different building representation techniques as well as the outputs of various simulations using fine and coarse grid sizes in order to analyze the results. For modelling floods in urban areas, a fine 2-D grid, typically less than 5 m, is required to accurately simulate the flow on streets, intersections, around houses and buildings 75 . In the beginning, we focused on the BB technique to determine whether or not the prepared DEM was suitable for such numerical simulation. Because we believe that the quality of the DEM that was prepared is at an acceptable level. In this case, we were looking for the answer to the question of whether or not this model would provide us with results that were satisfactory. In our study, we used three different grid sizes, starting at 8 m and the others at 10 and 20 m. In fact, because of the size of the area considered in the modeling in HEC-RAS 2-D, it was difficult to simulate the flow using a grid size smaller than 8 m. The fact should be noted, however, that shrinking the size of hydrodynamic grid cells results in denser mesh and therefore requires a longer run-time to complete 76 , 77 , 78 , necessitating a trade-off between simulation accuracy and calculation time. In a study by 79 , two novel methodologies for reducing the processing time of 2-D large-scale flood simulations are compared in order to evaluate their merits and drawbacks and provide advice for their effective application. Specifically, Yalcin 80 stated that mesh resolutions created at the basin scale with a size greater than 10 × 10 m, referred to as a "coarse grid," cause significant errors in the estimated inundation extent because they are unable to capture rapid changes in the terrain geometry.

To shed light on the role of grid size in numerical simulation, multiple simulations have been done. When the BB technique was simulated using cell sizes of 8, 10, and 20 m, the results of the simulations revealed an error in the water depth calculation. In front of the buildings, a large amount of water has accumulated. We believe that this error is due to the disparity between the dimensions of the street and the size of the cell (See Fig.  8 a, b, and c). When more precise cell sizes are utilized, it is anticipated that the error will decrease. Our attention was drawn to something, water propagation and water depth in front of buildings can be improved if the grid size is reduced. The DEM and mesh resolutions are the most significant elements to consider when running simulations of water level dynamics using the BB technique. On the other hand, the floodplain roughness coefficient is a crucial consideration for mapping the extent of floodplain. According to Alipour, et al. 44 , the resolution of the DEM is the most essential factor across all scales for the simulation of the dynamics of water levels. In their research on the flood inundation simulation of the Mahanadi River in Odisha, Surwase, et al. 81 found that the HEC-RAS model is sensitive to the manning roughness coefficient. Figures  8 a, b, and c show a random location within the 2-D geometry area to demonstrate flow propagation. Figure  9 illustrates the levels to which the inundation depth is sensitive to the grid size used in the BB technique simulations. Because these simulations give a false impression of the extent and depth of the flood, they should be ignored in most cases. Because of the capabilities of the computer processor, it was not possible to reduce the cell size to less than 8 m. A mesh of this size would be unable to accurately simulate the abrupt change in the terrain. As a result, we came to the conclusion that the size of the 2-D flow area needed to be reduced in order for us to be able to model the area using a grid size of 2 × 2 m or even less than 2 m.

Analysis of the numerical simulation using different mesh resolutions with the BB technique: ( a ) Grid size 8 × 8 m. ( b ) Grid size 10 × 10 m. c Grid size 20 × 20 m. These maps were processed and generated in ArcGIS 10.7 software (

Comparison of inundation depth between BB technique simulations.

This is not the end of the story because it is the responsibility of the researchers to investigate all possible avenues so that they can eventually present a conclusion to society. Because we were interested in determining the effect of urban flooding inside of the 120 m ring road in Erbil, we made the decision to model this zone using a different method, which is known as the BR technique. Previously, Mustafa and Szydłowski 43 have validated this method by applying it on a small scale to a physical model of the Toce river. The Manning coefficient is a coefficient describing the roughness or friction of a surface in the field of flow, that estimates the average flow velocity. In the BR technique, Manning coefficient values (such as 10 m −1/3  s) are assigned to all the mesh regions that represent the building blocks (which here are known as user-defined polygons) to examine the resistance against the flow. When compared to the BB techniques, the results demonstrated a more accurate estimation of the water depth within the same grid size and geometry area. In point of fact, the BR method allows for the possibility of water entering the houses and buildings, whereas the BB method ensures that this will not occur because the building is modelled in the form of a block. In terms of the calculation of water depth, BR may give better results, which is something we could say in response to the question of which method is more realistic. If a high-resolution DEM is used in the modeling and simulation process, it is expected that the BB technique will give more accurate results about the flood extent and the most vulnerable areas.

Assessments of the areas affected by flooding

We came to the realization that BR is an effective technique for conducting analysis on floods in the study area, obviously, we reached this conclusion due to the lack of reliable data. Hence, the analyses presented are based on the BR technique with a 10 m grid size. Moving on, it is clear that we made some assumptions in order to develop the model for the area considered in HEC-RAS 2-D, one of which was that there is no inflow to the area at all, which is not true because there is inflow to the 2-D area through main roads and some underground box culverts that cross the 120 m ring road. However, because there is no recorded data regarding the flow, we made the decision to keep the boundary closed. Despite this, we are aware that this assumption has an impact on the results; however, by constructing some retention basins, we can prevent flow from the outside of the studied area into the inside. Beyond assumptions, we can confidently state that our modeling is accurate to a significant degree because when comparing our results with those areas known as prone areas, the accumulation of water in the HEC-RAS 2-D is calculated.

Using two orthogonal components of the flow, 2-D surface flow modeling attempts to model the propagation of overland flow. It is possible to predict the maximum inundation area and the flow dynamics, such as water depth and velocity, using 2-D modeling of the surface flow 82 . When we look at the extent of the flood, it is immediately apparent that water has accumulated in low-lying areas. Flood accumulation areas are often identified by their low elevation, which is a good indicator of their risk of flooding 28 . Furthermore, despite changes in the city's layout, the flow movement continues to follow the same path that it did a hundred or even a 1000 years ago. For example, the source of accumulated water in both Tayrawa street, particularly Tayrawa Bazar, and the main gate of the council of ministers on 30 m street is coming from the northeastern areas of the studied areas, such as the North industrial area and the area near the Family Mall shopping center, according to the findings (Fig.  10 a). The source of the flow that causes problems in Setaqan quarter on 60 m street, then in Saydawa quarter near the old Saydawa bridge, and near Nishtiman Bazar, before finally passing through the city via an underground box culvert, is located in the eastern part of the study area, and it comes from the Havalan quarter (Fig.  10 b). When the volume of flow exceeds the capacity of the box culvert, overflows occur in this zone. This event occurs after heavy rainfalls for a variety of reasons, including the flow from the surrounding area being accumulated over there, the area serving as a flow route, the stormwater system at this location appearing to be inadequate, old and finally, the accumulation of debris inside inlets, manholes, and box culverts, which prevents the system from functioning properly.

Results of the numerical simulation using BR technique with grid size 10 × 10 m: ( a ) upper part of the studied area. ( b ) the lower part of the studied area. Base imagery sources: Esri, DigitalGlobe, GeoEye, i-cubed, USDA FSA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community. These maps were processed and generated in HEC-RAS 6.1 software ( https://www.hec.usace.army.mil/software/default.aspx ).

The inundation depth (m) maps that were generated over the course of the simulation run period are used as criteria to describe the extent of the inundated areas. Although the area of flood inundation and its depth are the most critical parameters, particularly when mapping flood hazards 83 . We chose to focus on the extent and prone areas of flooding rather than the depth of inundation because the surface flow is all that is calculated during simulations. For the reason that some of the surface runoff will pass through the existing stormwater system. In addition, we performed three separate simulations based on a theoretical probability distribution of 10, 5, and 1%, which is equivalent to 71.16, 83.21, and 113.49 mm, respectively (the duration of the rainfall event was 24 h).

Here, in order to delineate flood extent in the studied area, we generated a vector layer using water depth maps at a value of 0.2 m. This means that the program will develop a vector layer for all areas where the water depth is equal to and/or greater than 0.2 m. This was done so that we could determine the extent of the flooding. After that, the vector layer was saved by being transformed into a shapefile. The vector layer was then sorted using the attribute tables, and areas smaller than 500 m 2 were ignored. As can be seen in Fig.  11 a and b, the amount of rainfall that occurs will cause the flooded area to expand, and this expansion will be proportional to the amount of rainfall that occurs. When the simulation was performed with a rainfall probability of 10%, an area of about 5.725 km 2 was affected by flooding. The size of this affected area increased by about 21.83%, which is equivalent to 1.25 km 2 , when the rainfall probability was increased to 5%. In addition to this, when we simulated this time with a rainfall probability of 1%, it resulted in a 71.37% increase in the magnitude of the flood extent (Fig.  12 ). In point of fact, the areas of the studied site that experience water levels that are higher than 0.2 m in the case of P 1% rainfall have an area that is approximately equivalent to 10% (9.811 km 2 ) of the total area (102.38 km 2 ). It is concerning that the majority of the areas that flood or accumulate water as a result of rainfall are public streets, commercial districts, and residential areas. As a direct consequence of this, both citizens and businesses experience a loss of life as well as property. It is a common observation in Erbil that rain that falls in a concentrated burst over a short period of time causes the water level in the streets to rise, which in turn has a significant effect on the flow of traffic. Other flood hazard parameters, such as velocity, could not be developed by us because of the quality of the data that was available and the level of uncertainty that we produced during the modelling process. It was mentioned that only 10.71% of the studied area is covered by vegetation, and the majority of this vegetation can be found in two large areas in the middle of the city. Because the permeable areas were not distributed well, there was less infiltration and more runoff as a result.

Comparison of the development of flooded areas based on a different rainfall simulation: ( a ) Gate to council of ministers. ( b ) Nishtman Bazar, Saydawa quarter and Setaqan quarter. Base imagery sources: Esri, DigitalGlobe, GeoEye, i-cubed, USDA FSA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community. These maps were processed and generated in ArcGIS 10.7 software (

The evolution of inundated areas.

Observing two extraordinary events that occurred at the end of 2021, authorities in Erbil revealed that the flooded area is located on the route of natural and seasonal streams, which occurred outside the area considered in the HEC-RAS 2-D modeling in the current study. The expansion of the city has resulted in the construction of numerous residential and commercial buildings, as well as industrial and manufacturing facilities, along the path of natural flow routes. In this section, we evaluated the areas that were at risk of flooding outside of the 120 m ring road by using the DEM with a resolution of 30 m to assess flood basins that had been delineated. The route of the natural streams can clearly be seen in Fig.  13 , which shows that both Zerin city and Korean village are located along the route of the natural streams. According to a media statement issued by the governor of Erbil on October 30, 2021, an amount of 55 mm of rainfall was recorded in the upper part of the city in just two hours on that day. In the northeast, where there is higher topography known as the Tarin heights, crazy flow can flow to the prone areas.

Some inundated areas in Erbil during the storm event of October 30 and December 17, 2021. Base imagery sources: Esri, DigitalGlobe, GeoEye, i-cubed, USDA FSA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community. This map is processed and generated in ArcGIS 10.7 software (

The same can be said for the village of Grd Jutiar, which is located directly adjacent to the natural canal. In fact, on that particular day, the canal was unable to handle the volume of water flowing through it. As a result of this, the overflow of canal banks occurred somewhere near the north side of the village, resulting in the catastrophic event. The first phase of a 150 m ring road connecting the main Shaqlawa road with the main Bahrka road was completed in 2021. In an interview with Rudaw TV 84 , the project manager for the 150 m ring road stated that the culverts and box culverts that cross the ring road and run along the ring road were only intended to handle stormwater from the surrounding areas and household waters, not the large amounts of water that flow from the natural basin. Erbil city has expanded toward mainly the Northeast and East areas, but detailed hydrologic studies are absent. Many stormwater and sewer pipes in local areas throughout Erbil have been built without taking the dimensions of water pathways and streams into consideration. It is now possible to experience flash flooding in areas where urban and infrastructure development has taken place.

Flooding in Erbil ranges from minor incidents, such as inundation of streets and then water entering some houses, to major incidents, such as large areas of the city being submerged for several hours at a time. The event, which took place on December 17, 2021, was primarily focused on the Southeast of the city, specifically the Bnaslawa sub-district and the Roshinbiri quarter (Fig.  14 ). In reality, this was a catastrophic event that was unprecedented in Erbil's history. Because 12 people died, one of them was a 10-month-old child whose body was found approximately 60 days after the event and more than 15 km away from his house. A large number of small-scale local problems are common in most developing cities around the world, primarily because their stormwater systems do not have enough capacity to handle heavy rainstorms 85 . Greater flooding risk exists in areas that are close to the main channel and accumulation path 86 . Poorly designed highways that do not take into account natural drainage patterns can lead to increased runoff and flooding during heavy rainfall events 87 , 88 . There were various contributing factors to this catastrophic event, the first of which was a reduction in the cross-section of streams, with their bed elevations approaching the elevation of the street in some places. The reason for this is that these seasonal streams have not been cleaned in a long time and have become clogged with river sediments and debris. In addition, a large number of quarries are operating on the river bed on the upstream side of the developed area (Bnaslawa sub-district) to extract sub-base or other materials. According to the locals' speech, those quarries created a dam-like barrier, which collected a large volume of water on that particular day before being breached, causing the flow to become increasingly erratic. As we can clearly see, a large number of residential areas have been constructed directly adjacent to stream routes, indicating that this type of event is predictable.

Bnaslawa sub-district and the Roshinbiri quarter were inundated in Erbil during the storm event of December 17, 2021. Base imagery sources: Esri, DigitalGlobe, GeoEye, i-cubed, USDA FSA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community. This map is processed and generated in ArcGIS 10.7 software (

The floods in Erbil cause broad damage on several levels (Fig.  15 ). On a human level, floods claim a number of lives. Economically, urban areas are the most frequently affected, and this is especially true in the most severe events. Environmental consequences are big, and we are seeing deterioration of the natural environment, as well as the production of debris and wreckage, which is being spread over drainage lines and residential areas. There are several different approaches that can be taken to mitigate the consequences of flooding and heavy rainfall. One of the strategies is to make individuals aware of locations that are at risk of flooding and to warn them accordingly. For example in Brazil, a Decision Support System (DSS) coupled with a flood alert web application was developed and evaluated in the Prosa Basin (Midwestern Brazil) to send early flood warning messages to ordinary people 89 . The basis of the flood alarm system was the Hydrologic Modeling System (HEC-HMS) and River Analysis System (HEC-RAS) of the Hydrologic Engineering Center.

Flooding had devastating consequences in Erbil in two separate events at the end of 2021.

Recommendations, suggestions and the future scope

In accordance with the findings of this study, the recommendations made priorities the implementation of a plan for flood hazard prevention and the protection of the city and its infrastructure through the maintenance of existing floodwater drainage facilities. The result of this study highlights the necessity of establishing hydrodynamic facilities for the control, obstruction, and divergence of the floods of drainage lines, and the specific recommendations are as follows:

The adoption of a plan to harvest water in the northeast and east of the city would make a significant contribution to the provision of water for people and farms. It would also aid in the process of afforestation, which slows down floods and allows them to feed the underground reservoirs. At the same time, it would reduce a portion of the wasting floods that are directed towards the city center. Moreover, in order to reduce the craziness of the flow and delay the flow into the city.

Cleaning and maintaining the width of seasonal streams and drainage lines, which are located in various parts of the city, especially those located in the east, the northeast and the southeast. Also necessary is the refinement of the slope of the drainage channel in the area in order to increase the drainage velocity.

A reserve for each stream must be established to prevent construction in drainage lines and flood catchments. This reserve must remain in place even after the proposed man-made channels have been constructed. A mandatory study of flood risks, including their peaks and catchments, must also be provided with each project and submitted to the appropriate authorities for consideration of approving the project.

The stormwater management system should be changed/modified so that it can keep up with urban development, population growth, and climate change. Because there was no way to show that they were the same.

Green roofs, rainwater harvesting systems in the household, permeable surfaces, swales, channels and rills, infiltration trenches, detention and infiltration basins, rain gardens, and retention ponds are all examples of Nature-Based Solutions (NBS) that can be used to improve the capacity of stormwater systems. Certainly, this will be after evaluating the outcomes of each solution using high-resolution models and selecting the most suitable option for the research area.

The uneven distribution of the city's greenery has contributed to the problem of increased runoff. One way to lessen the impact of this is to reorganize the green spaces within the city layout. In this regard, precautions should be taken in areas that are prone to flooding.

Local and regional authorities should develop flood control and protection legislation and regulations in order to save lives and property from the effects of flooding. Having such types of national laws in place is extremely important for managing flood risk and increasing future flood resilience in floodplains.

The Storm Water Management Model (SWMM) or a coupled model can also be used to evaluate the efficiency of the current urban drainage system in Erbil city center, which will allow for a more accurate analysis of urban flooding. However, because there are currently no GIS-based stormwater lines in Erbil, a significant amount of effort may be required. The model can simulate storm events and the resulting flooding scenarios and shall help the authorities in the directorate of water and sewer/Erbil devise an efficient drainage system in the city. Filling in the gaps in the current study will result in a completely different understanding of the Erbil flooding process in the future, which will aid the authorities in developing a more comprehensive flood management and mitigation plan.

Conclusions

Climate change, which causes and amplifies large-scale natural disasters, poses a threat to the city of Erbil. These dangers can sometimes have a negative impact on people's daily lives and activities in the city. Our previous paper clearly illustrates the magnitude of the flooding phenomenon that has occurred in this area. Flash floods in urban areas have been and will continue to be a major problem in many cities throughout the world, particularly in developing countries. The threat of flooding can be countered by the opportunity it provides to bring in more water. As a consequence of this, flood management is a component of water management, and it should be given particular consideration in the Kurdistan Region of Iraq, particularly in the city center of Erbil, where solutions to the problem of water scarcity are required as quickly as possible. Due to the rapid growth of Erbil as a city in a developing country without the necessary funds to expand and renovate their existing drainage systems, the situation continues to deteriorate further. The findings of this study tell us that the effects of flash flooding in Erbil in the areas shown are due to their location that is located on the waterways, and even the areas that were flooded in the first month of 2022 in the city center were waterways in the past. Therefore, we believe that serious and practical steps must be taken in order to lessen the effects of floods, which will allow for runoff to be collected, utilized, and stored in order to increase groundwater levels. Currently, certain areas of the city are experiencing water shortages during the warm summer months, and the level of groundwater has decreased by a sizeable level.

In order to shed some light on the crucial role that data plays in the preparation of hydrological and hydrodynamic models, we must keep in mind that obtaining data in developing countries is not an easy task. There are difficulties and challenges to overcome at each stage. Even if the goal is to develop a simple flood model, we face obstacles and challenges. During the course of this work, we tested a number of different approaches to prepare the hydrodynamic model. In the end, we were successful in employing the BR technique to construct a model with cell size (10 * 10). In point of fact, we were able to draw the conclusion, on the basis of our observations, that the BR technique is adequate for modelling flash floods in regions where there is a scarcity of data.

Data availability

The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.

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Mustafa, A., Szydłowski, M., Veysipanah, M. et al. GIS-based hydrodynamic modeling for urban flood mitigation in fast-growing regions: a case study of Erbil, Kurdistan Region of Iraq. Sci Rep 13 , 8935 (2023). https://doi.org/10.1038/s41598-023-36138-9

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The 2015 Chennai Flood: A Case for Developing City Resilience Strategies

Soumita Chakraborty , Umamaheshwaran Rajasekar

Over the last 25 years, the world has seen a rise in the frequency of natural disasters in rich and poor countries alike. Today, there are more people at risk from natural hazards than ever before, with those in developing countries particularly at risk. This essay series is intended to explore measures that have been taken, and could be taken, in order to improve responses to the threat or occurrence of natural disasters in the MENA and Indo-Pacific regions. Read More . ..  

The Chennai metropolitan region (CMA), with an area of 1,189 sq kms and a population of 8,653,521, is the fourth-largest populated city in India. [1] This city, located in north eastern part of Tamil Nadu is a flat plain bounded on the east by Bay of Bengal and on the remaining three sides by Chengalpattu and Thiruvallur districts. Expansion in terms of area as well as population has led to a shift in land use and land cover patterns across the region.

Situated along the eastern coast of India, Chennai is exposed to violent storm surges and flooding during northeast monsoons (September to November). Although local flooding is an annual phenomenon in selected parts of the city, extreme events, such as the 1918 cyclone and 1985 floods, had faded from people’s memory. [2]  However, history repeated itself in the city and neighboring coastal districts in November-December 2015, when a devastating flood affected more than 4 million people, claimed more than 470 lives and resulted in enormous economic loss. [3]

The sudden and unprecedented nature of the flood led to ad hoc and uncoordinated relief and response activities by different governmental and non-governmental agencies. Industrial and commercial centers were forced to temporarily shut down their production due to loss of power, shelter and limited logistics. Amid the chaos and widespread impact, the event brought people and institutions in and outside Chennai together, to provide support to the victims affected by the flood. Help reached the affected areas and their residents from different sections of society and in variety of forms. The lessons from this case study and others like it can help urban centers elsewhere in Asia to plan for similar eventualities.

Challenges Faced During and Following the Event

Flooding often handicaps the affected community by adversely affecting its educational system, food availability, mobility and access to energy on a daily basis. Chennai was no exception: daily functions became a challenge for the entire city.

School authorities faced numerous challenges, ranging from the sudden need to shift and secure school records / admit cards and postpone exams, to maintaining physical infrastructure and equipping schools to serve as shelters. Following the event, school authorities faced yet another set of daunting tasks related to the resumption of the academic session (e.g. repairing and replacing furniture, etc.) in schools that had been shuttered (for 10 to 33 days) in various parts of the city.

Flooding often handicaps the affected community by adversely affecting its educational system, food availability, mobility and access to energy on a daily basis.

Food logistics arrangements across the affected communities included the unavailability of manufacturing capacity and delivery mechanisms. The lack of accessibility to several parts of Chennai due to severe flooding made identification of delivery points and transport routes more difficult, which deprived some local communities of basic food supplies required for survival. During the first 24 hours of flooding, the main concern of the local supermarkets providing food supplies to surrounding areas, was to safeguard perishable items not only from getting wet but also to keep them from spoiling (since there was no electricity). However, it was critical for them to meet customer demand, keeping in mind the limited food availability and lack of communication within their management team.

First responders and information providers faced difficulties in providing accurate real time information to local communities on flooded areas, accessibility of roads, road condition, traffic flow and current weather scenario.

Flooding of roads, tracks and supporting infrastructure, delayed and suspended provision of necessary services. Moreover, several hospital staff were unable to get to work or extend their support due to being affected by the flood themselves. It was a greater challenge for hospital authorities, to safeguard patients admitted to Intensive and Critical Care units (ICU) or those under ventilation through maintenance of power supply.

The Chennai flood had a devastating impact on businesses, especially on small and medium-sized enterprises (SMEs), who were unprepared and vulnerable to both direct and indirect impacts. Flood water entered the first level of most of the offices and shops, reaching a height of approximately two meters in some areas. This damaged products, stocks, storage units, electrical equipment. In post disaster scenario, several businessmen in Chennai were unable to operate for three months due to lack of process-service delivery, finance, logistics, management implications and loss of customer base. Service station owners too had a hard time in recovering broken cars, fixing damaged engines, car interiors, upholsteries and external impact damages. In post flood scenario fungal attack and rusting were additional issues faced by them to continue their business.

Community-Based Organizations (CBOs) faced a plethora of challenges and obstacles, as did official first responders ...

Community-Based Organizations (CBOs) faced tough challenges, such as contingency planning at zone/ district level, stock piling of relief materials/supplies, arranging for inter-agency coordination, preparing evacuation plans, providing public information and conducting field exercises. Service providers in the transport sector had to undertake route planning and ensure priority management. Situation worsened due to lack of mechanisms to mitigate impacts of flood, such as road closure notification, absence of traffic control warning signs, emergency detour routes, etc. which are essential during such extreme events. Thus, they procured boats and hired fishermen to commute to inundated parts of the city.

Likewise, government officials — first responders, such as the fire department, the National Disaster Response Force (NDRF) and the police, in particular — faced a plethora of challenges and obstacles. They not only had the responsibility of conducting rescue operations, but also of road clearance and provision of other facilities to ensure supply of basic necessities throughout the affected communities. The fire department managed calls, coordinated between departments and controlled water distribution system, in the absence of power for prolonged periods. They had to function with disrupted utility services, clear streets of debris, waste and fallen trees in low lying areas and also ensure steady and quick pumping out of water from flooded pockets. NDRF on the other hand, was required to conduct timely rescue operations with small teams, coordinate with local officials, mobilize limited human resources to priority areas and commute using limited transport vehicles and boats. They also had electricity constraints in setting up onsite operational coordination control room (OSOCC) and shelters for both their team as well as the local community. In some instances, the Chennai police were unable to ensure effective and timely response, due to lack of common command system, clear assignment of duties and demarcation of roles to respective officials, for times of emergency.

Resilience Efforts

Various segments of society assisted local communities and relief providers in affected parts of Chennai to cope with the flood. The Chennai government, private schools and the Parent Association were three strong pillars which supported victims in the aftermath of the flood. School children from Hosur made artefacts for sale at an art show to raise funds for a severely affected government school in Poonamallee. Another group of 15 teachers and 40 alumni of the TVS Academy School of Hosur, travelled to Chennai to help improve the infrastructure of Aringar Anna Government Girls Higher Secondary School, Poonamallee. These groups extended help in painting damaged walls, blackboards and building new toilets. During and post flood, government schools were used as relief camps where food and health issues were partially covered by government and parent association.

Various segments of society assisted local communities and relief providers in affected parts of Chennai to cope with the flood.

Private enterprises, such as restaurants, taxi service providers and automobile service centers, also joined hands with the government to provide relief to the flood affected population. Kolapasi, a Chennai-based restaurant, was turned into a temporary food relief agency. Social media was used for awareness generation on the initiative and also to raise funds. Individuals of all age groups and across all professions, supported this initiative by volunteering to cook, wash utensils, pack and deliver food. About 1.7 lakhs food boxes were distributed across the city.

The ride-hailing company Ola started operating boats, which also provided an important learning for future preparedness measures. They strategically identified water routes for providing service to even the most inaccessible areas. They also helped the Fire Department in conducting their rescue operations. Similarly, a vegetable and milk supply chain, Heritage Fresh, sold their commodities at a subsidized rate when prices in parts of Chennai were on the rise. Mobile vegetable shops also put in efforts to reach out to as many flood affected people as possible. Online food service providers, such as Zomato, added one extra meal on behalf of the company for every order that was placed for the stranded people.

The impact of flood on health sector was a complex issue, as the threats to health were both direct (for example, flash flood) and indirect (for example, a hospital needing to be closed due to flooding). To protect and promote health of patients and minimize health risks, sustained treatment for chronic infectious disease were provided through voluntary camps. 51 patients were evacuated and ICU wards were shifted to first floor; special care was taken while shifting new born babies, mental patients, elderly or patients with disabilities; cleanliness was ensured by internal experts using prescribed norms and dosage of chemicals and sump pumps were installed in hospitals to drain out water. Adequate stock of medicine, injections and IV fluids (intravenous) were available for continued medical care of the patients. Immediate actions in response to the flash flood situation from the ESIC was to direct all capacities of the existing health care system towards flood relief, prevention of disease outbreak, water disinfection and vigilance for future outbreaks.

Funds for energy and fuel supply were of least priority, but their demand was high in slums and remote areas where it was required for the survival of sick family members, the elderly and children. Organizations like Oxfam, provided support through the provision of energy and fuel supply to households. Private companies like Servals Pvt Ltd. initiated a similar program of providing specially designed rehabilitation kit, which included a kerosene stove, water filter, utensils, disinfectant, etc. to the slum dwellers, manual laborers and villagers in the worst hit areas, who were not covered under government programs. Along with the kit, training was also provided to ensure optimum utilization of the given products. 

Small- and medium-sized enterprises (SMEs) suffered both direct (physical) and indirect (man-days/ sales) loss. They demanded government to provide interest free loans and delay their tax payment along with other repayments. SMEs took adequate measures to build resilience against future floods through installation of electrical points at a raised height and flood defense barriers within their premises, securing databases by using online recovery systems, etc.

Vehicle service stations, such as Harsha Toyota collected and repaired cars that broke down due to water logging. Company ordered its dealerships to take extra space for flood affected cars while insurance companies were asked to clear their claims on time. They also provided discounted service packages, such as completely waiving labor charges, and offering ten percent discounts on spare parts, roadside assistance, loyalty points of up to Rs. 20,000, 50 percent discounts on car renewal and an exchange bonus up to Rs. 30,000 to flood-affected areas. The 2015 Chennai flash flood made all the car companies (e.g., Toyota, BMW, Renault, Maruti, Hyundai, Nissan, etc.) rethink and develop more sustainable business continuity plan for production, maintenance and parking. Several online and local sellers including a number of automobile portals, such as Copart, has a separate page exclusively for cars damaged in Chennai floods for holding auctions.

Hotel authority liaised with local authorities (i.e., police and fire service and incorporated emergency plans and services wherever possible. Guests were relocated and although flood kits (water proof clothing, blanket, candle/torches, etc.) was provided to all, there is a need to strengthen response and relief capacity of hotels.

Community-Based Organizations (CBOs), such as Tamil Nadu Thowheed Jamath (TNTJ) mobilized over 700 volunteers for carrying out rescue, relief, rehabilitation and reconstruction work, which included arranging food, shelter, cleaning up after flood water resided, waste management, spraying of insecticides and distribution of relief kit. They used half-cut plastic tank boats to rescue stranded people, conducted community based training programmes in health risks and fostered behavioral changes to support all social groups. TNTJ also became one of the coordinating facilitator through establishment of community, zone and district level mechanism with local partners, frontline workers and line departments.

Social media, such as Facebook, Twitter, and Google Maps, played an important role in bringing all the service providers and individuals to work together for reducing the impact and helping the flood affected population recover better. These platforms helped disseminate information, broadcast further warnings, inform people of the undertaken initiatives, call for volunteers in respective sectors, crowdsource and map the waterlogged or inundated areas. Professor Amit Sheth and his team at Wright State University in the United States carried out a new National Science Fund (NSF)-funded project, the Social and Physical Sensing Enabled Decision Support for Disaster Management and Response. This technology was mobilized  to monitor and analyze social media and crowdsourcing for better situational awareness of Chennai flood. Companies, such as BSNL, Paytm, Airtel and Zomato, also pitched in to help Chennai flood victims.

Towards Building Urban Disaster Risk Resilience

The 2015 Chennai flood caused by the torrential downpour brought city life to a standstill. It affected socio-economic condition of the district, maimed critical infrastructure, stranded animals and humans, disrupted services and flooded major parts of the city. The incorporation of flood preparedness measures will help reduce the extent of their impact on people, their life and property in future, along with giving them better coping abilities.

Best practices from Chennai flood case study should be used to strengthen existing risk handling capacities as well as learn lessons, to help replicate similar initiatives for preparedness of other Indian cities. This will also enable the government to coordinate and collaborate with similar service providers across the city for conducting efficient rescue and response operations in future. Best practices extrapolated from this case study could also prove useful to local and national officials from countries throughout Asia and the Middle East, all of whom continue to wrestle with the complex challenges associated with responding to responding to natural disasters in urban settings.    

Prioritized interventions and emergency responses which can be used to reduce urban risk, redevelop city plans and ensure effective disaster relief operations in future are listed below.

➢ As was reflected in the initiatives undertaken by several CBOS, particularly TNTJ, disaster response should address the humanitarian imperative; adhere to the principles of neutrality and impartiality; and ensure local participation and accountability, along with respecting local culture and custom. Thus, awareness generation and capacity building programs should promote inclusive flood disaster management approaches. Operational and sustainable livelihood models should be developed in the aftermath of such emergencies for weaker sections of the society. Disaster resistant shelters, public buildings and critical infrastructure, such as water and sewerage networks, need to be improved in order to avoid water logging and enhance community resilience.

➢ Cities need to develop broadcasting systems to inform the affected community about real time extreme events in different locales and provide updates on current road, flood, weather, food and energy supply scenario. Social media helps develop a two-way communication which helps acquire real time information from the community itself.

➢ Development of city disaster risk resilience strategy will better enable government and non-government organizations in phasing out adaptation and mitigation measures during normalcy.

➢ To ensure community level disaster preparedness, designed trainings should include actions or steps to be taken by citizen prior to, during and after disaster scenarios. Emergency respondents need to have basic first aid skills, such as airway management, bleeding control and simple triage.

➢ Emotional impact of the event on both workers as well as victims need to be addressed and documented for informing city disaster management plan.

➢ GIS-based evacuation plans, including current flood water flow, emergency routes, water depth, obstacles and possible search and rescue (SAR) interventions, need to be prepared. Existing capacity needs to be strengthened and assistance programmes should be provided to existing or new SAR teams at district and state level, for future preparedness. In addition, there is also a need to prepare Flood Risk Maps highlighting availability of grocery stores, restaurants, public utilities, food storage units, hospitals, residential homes for elderly people, high flood prone areas, etc.

➢ Communication systems, including early warning and public awareness mechanisms, need to be established in order to disseminate information during adverse conditions. (There is also an urgent need to prioritize child protection for the prevention of child trafficking during disasters.)

➢ Adaptation strategies need to ensure raised utility and reduced food cost through development and strengthening of local food suppliers. Food supply chain should be maintained by improved coordination and efficiency between producers, suppliers and retailers.

➢ Local flood plain maps, should inform construction practices (e.g., selection of appropriate materials for walls and floors).

➢ In flood-prone areas, water proofing should be mandated for emergency facilities like- power control room, water treatment plants, sewerage plants, etc. Emergency food and assets (generator sets, fuel) area should be at an elevated level to prevent inundation due to flooding.

Note: The detailed assessment of interventions undertaken during and post Chennai floods was funded by Rockefeller Foundation under the Asian Cities Climate Change Resilience Network program. The study was conducted by Taru Leading Edge and IFMR Chennai.

[1] “Chennai Metropolitan Urban Region Population 2011 Census,” accessed May 29, 2017, http://www.census2011.co.in/census/metropolitan/435-chennai.html .

[2] Deepa H. Ramakrishnan, “Memories of Rain Ravaged Madras,” The Hindu, December 9, 2015, accessed May 29, 2017, http://www.thehindu.com/news/cities/chennai/floods-in-madras-over-years… .

[3] “Letter from Chennai- Saving a home from floods,” The National, January 17, 2015, accessed May 29, 2017, http://www.thenational.ae/world/south-asia/20151213/letter-fromchennai-saving-a-home-from-the-floods ; “When Chennai was logged out and how,” Deccan Chronicle, accessed March 29, 2017; and http://www.deccanchronicle.com/151203/nation-currentaffairs/article/when-chennai- was-logged-out-and-how.B. Narasimhan, “Storm water drainage of Chennai: Lacuna, Assets, and Way Forward.” Presentation made at “Resilient Chennai: Summit on Urban Flooding,” hosted by 100 Resilient Cities in partnership with the Corporation of Chennai (2016). 

The Middle East Institute (MEI) is an independent, non-partisan, non-for-profit, educational organization. It does not engage in advocacy and its scholars’ opinions are their own. MEI welcomes financial donations, but retains sole editorial control over its work and its publications reflect only the authors’ views. For a listing of MEI donors, please click here .

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Disaster Management in Flash Floods in Leh (Ladakh): A Case Study

Preeti gupta.

Regimental Medical Officer, Leh, Ladakh, India

Anurag Khanna

1 Commanding Officer, Army Hospital, Leh, India

2 Registrar, Army Hospital, Leh, India

Background:

On August 6, 2010, in the dark of the midnight, there were flash floods due to cloud burst in Leh in Ladakh region of North India. It rained 14 inches in 2 hours, causing loss of human life and destruction. The civil hospital of Leh was badly damaged and rendered dysfunctional. Search and rescue operations were launched by the Indian Army immediately after the disaster. The injured and the dead were shifted to Army Hospital, Leh, and mass casualty management was started by the army doctors while relief work was mounted by the army and civil administration.

The present study was done to document disaster management strategies and approaches and to assesses the impact of flash floods on human lives, health hazards, and future implications of a natural disaster.

Materials and Methods:

The approach used was both quantitative as well as qualitative. It included data collection from the primary sources of the district collectorate, interviews with the district civil administration, health officials, and army officials who organized rescue operations, restoration of communication and transport, mass casualty management, and informal discussions with local residents.

234 persons died and over 800 were reported missing. Almost half of the people who died were local residents (49.6%) and foreigners (10.2%). Age-wise analysis of the deaths shows that the majority of deaths were reported in the age group of 25–50 years, accounting for 44.4% of deaths, followed by the 11–25-year age group with 22.2% deaths. The gender analysis showed that 61.5% were males and 38.5% were females. A further analysis showed that more females died in the age groups <10 years and ≥50 years.

Conclusions:

Disaster preparedness is critical, particularly in natural disasters. The Army's immediate search, rescue, and relief operations and mass casualty management effectively and efficiently mitigated the impact of flash floods, and restored normal life.

Introduction

In the midnight of August 6, 2010, Leh in Ladakh region of North India received a heavy downpour. The cloud burst occurred all of a sudden that caught everyone unawares. Within a short span of about 2 h, it recorded a rainfall of 14 inches. There were flash floods, and the Indus River and its tributaries and waterways were overflowing. As many as 234 people were killed, 800 were injured, and many went missing, perhaps washed away with the gorging rivers and waterways. There was vast destruction all around. Over 1000 houses collapsed. Men, women, and children were buried under the debris. The local communication networks and transport services were severely affected. The main telephone exchange and mobile network system (BSNL), which was the lifeline in the far-flung parts of the region, was completely destroyed. Leh airport was flooded and the runway was covered with debris, making it non-functional. Road transport was badly disrupted as roads were washed away and blocked with debris at many places. The civil medical and health facilities were also severely affected, as the lone district civil hospital was flooded and filled with debris.

Materials and Methods

The present case study is based on the authors’ own experience of managing a natural disaster caused by the flash floods. The paper presents a firsthand description of a disaster and its prompt management. The data was collected from the records of the district civil administration, the civil hospital, and the Army Hospital, Leh. The approach used was both quantitative as well as qualitative. It included data collection from the primary sources of the district collectorate, interviews with the district civil administration and army officials who organized rescue operations, restoration of communication, and transport, mass casualty management, and informal discussions with local residents.

Disaster management strategies

Three core disaster management strategies were adopted to manage the crisis. These strategies included: i) Response, rescue, and relief operations, ii) Mass casualty management, and iii) Rehabilitation.

Response, rescue, and relief operations

The initial response was carried out immediately by the Government of India. The rescue and relief work was led by the Indian Army, along with the State Government of Jammu and Kashmir, Central Reserve Police Force (CRPF), and Indo-Tibetan Border Police (ITBP). The Indian Army activated the disaster management system immediately, which is always kept in full preparedness as per the standard army protocols and procedures.

There were just two hospitals in the area: the government civil hospital (SNM Hospital) and Army Hospital. During the flash floods, the government civil hospital was flooded and rendered dysfunctional. Although the National Disaster Management Act( 1 ) was in place, with the government civil hospital being under strain, the applicability of the act was hampered. The Army Hospital quickly responded through rescue and relief operations and mass casualty management. By dawn, massive search operations were started with the help of civil authorities and local people. The patients admitted in the civil hospital were evacuated to the Army Hospital, Leh in army helicopters.

The runway of Leh airport was cleared up within a few hours after the disaster so that speedy inflow of supplies could be carried out along with the evacuation of the casualties requiring tertiary level healthcare to the Army Command Hospital in Chandigarh. The work to make the roads operational was started soon after the disaster. The army engineers had started rebuilding the collapsed bridges by the second day. Though the main mobile network was dysfunctional, the other mobile network (Airtel) still worked with limited connectivity in the far-flung areas of the mountains. The army communication system was the main and the only channel of communication for managing and coordinating the rescue and relief operations.

Mass casualty management

All casualties were taken to the Army Hospital, Leh. Severely injured people were evacuated from distant locations by helicopters, directly landing on the helipad of the Army Hospital. In order to reinforce the medical staff, nurses were flown in from the Super Specialty Army Hospital (Research and Referral), New Delhi, to handle the flow of casualties by the third day following the disaster. National Disaster Cell kept medical teams ready in Chandigarh in case they were required. The mortuary of the government civil hospital was still functional where all the dead bodies were taken, while the injured were handled by Army Hospital, Leh.

Army Hospital, Leh converted its auditorium into a crisis expansion ward. The injured started coming in around 0200 hrs on August 6, 2010. They were given first aid and were provided with dry clothes. A majority of the patients had multiple injuries. Those who sustained fractures were evacuated to Army Command Hospital, Chandigarh, by the Army's helicopters, after first aid. Healthcare staff from the government civil hospital joined the Army Hospital, Leh to assist them. In the meanwhile, medical equipment and drugs were transferred from the flooded and damaged government civil hospital to one of the nearby buildings where they could receive the casualties. By the third day following the disaster, the operation theatre of the government civil hospital was made functional. Table 1 gives the details of the patients admitted at the Army Hospital.

Admissions in the Army Hospital, Leh

The analysis of the data showed that majority of the people who lost their lives were mainly local residents (49.6%). Among the dead, there were 10.3% foreign nationals as well [ Table 2 ]. The age-wise analysis of the deaths showed that the majority of deaths were reported in the age group 26–50 years, accounting for 44.4% of deaths, followed by 11–25 year group with 22.2% deaths.

Number of deaths according to status of residence

The gender analysis showed that 61.5% were males among the dead, and 38.5% were females. A further analysis showed that more females died in <10 years and ≥50 years age group, being 62.5% and 57.1%, respectively [ Table 3 ].

Age and sex distribution of deaths

Victims who survived the disaster were admitted to the Army Hospital, Leh. Over 90% of them suffered traumatic injuries, with nearly half of them being major traumatic injuries. About 3% suffered from cold injuries and 6.7% as medical emergencies [ Table 4 ].

Distribution according to nature of casualty among the hospitalized victims

Rehabilitation

Shelter and relief.

Due to flash floods, several houses were destroyed. The families were transferred to tents provided by the Indian Army and government and non-government agencies. The need for permanent shelter for these people emerged as a major task. The Prime Minister of India announced Rs. 100,000 as an ex-gratia to the next of kin of each of those killed, and relief to the injured. Another Rs. 100,000 each would be paid to the next of kin of the deceased from the Chief Minister's Relief Fund of the State Government.

Supply of essential items

The Army maintains an inventory of essential medicines and supplies in readiness as a part of routing emergency preparedness. The essential non-food items were airlifted to the affected areas. These included blankets, tents, gum boots, and clothes. Gloves and masks were provided for the persons who were working to clear the debris from the roads and near the affected buildings.

Water, sanitation, and hygiene

Public Health is seriously threatened in disasters, especially due to lack of water supply and sanitation. People having lost their homes and living in temporary shelters (tents) puts a great strain on water and sanitation facilities. The pumping station was washed away, thus disrupting water supply in the Leh Township. A large number of toilets became non-functional as they were filled with silt, as houses were built at the foothills of the Himalayan Mountains. Temporary arrangements of deep trench latrines were made while the army engineers made field flush latrines for use by the troops.

Water was stagnant and there was the risk of contamination by mud or dead bodies buried in the debris, thus making the quality of drinking water questionable. Therefore, water purification units were installed and established. The National Disaster Response Force (NDRF) airlifted a water storage system (Emergency Rescue Unit), which could provide 11,000 L of pure water. Further, super-chlorination was done at all the water points in the army establishments. To deal with fly menace in the entire area, anti-fly measures were taken up actively and intensely.

Food and nutrition

There was an impending high risk of food shortage and crisis of hunger and malnutrition. The majority of food supply came from the plains and low-lying areas in North India through the major transport routes Leh–Srinagar and Leh–Manali national highways. These routes are non-functional for most part of the winter. The local agricultural and vegetable cultivation has always been scanty due to extreme cold weather. The food supplies took a further setback due to the unpredicted heavy downpour. Food storage facilities were also flooded and washed away. Government agencies, nongovernmental organizations, and the Indian Army immediately established food supply and distribution system in the affected areas from their food stores and airlifting food supplies from other parts of the country.

There was a high risk of water-borne diseases following the disaster. Many human bodies were washed away and suspected to have contaminated water bodies. There was an increased fly menace. There was an urgent need to prevent disease transmission due to contaminated drinking water sources and flies. There was also a need to rehabilitate people who suffered from crush injuries sustained during the disaster. The public health facilities, especially, the primary health centers and sub-health centers, were not adequately equipped and were poorly connected by roads to the main city of Leh. Due to difficult accessibility, it took many hours to move casualties from the far-flung areas, worsening the crisis and rescue and relief operations. The population would have a higher risk of mental health problems like post-traumatic stress disorder, deprivation, and depression. Therefore, relief and rehabilitation would include increased awareness of the symptoms of post-traumatic stress disorder and its alleviation through education on developing coping mechanisms.

Economic impact

Although it would be too early to estimate the impact on economy, the economy of the region would be severely affected due to the disaster. The scanty local vegetable and grain cultivation was destroyed by the heavy rains. Many houses were destroyed where people had invested all their savings. Tourism was the main source of income for the local people in the region. The summer season is the peak tourist season in Ladakh and that is when the natural disaster took place. A large number of people came from within India and other countries for trekking in the region. Because of the disaster, tourism was adversely affected. The disaster would have a long-term economic impact as it would take a long time to rebuild the infrastructure and also to build the confidence of the tourists.

The floods put an immense pressure and an economic burden on the local people and would also influence their health-seeking behavior and health expenditure.

Political context

The disaster became a security threat. The area has a high strategic importance, being at the line of control with China and Pakistan. The Indian Army is present in the region to defend the country's borders. The civil administration is with the Leh Autonomous Hill Development Council (LAHDC) under the state government of Jammu and Kashmir.

Conclusions

It is impossible to anticipate natural disasters such as flash floods. However, disaster preparedness plans and protocols in the civil administration and public health systems could be very helpful in rescue and relief and in reducing casualties and adverse impact on the human life and socio economic conditions.( 2 ) However, the health systems in India lack such disaster preparedness plans and training.( 3 ) In the present case, presence of the Indian Army that has standard disaster management plans and protocols for planning, training, and regular drills of the army personnel, logistics and supply, transport, and communication made it possible to immediately mount search, rescue, and relief operations and mass casualty management. Not only the disaster management plans were in readiness, but continuous and regular training and drills of the army personnel in rescue and relief operations, and logistics and communication, could effectively facilitate the disaster management operations.

Effective communication was crucial for effective coordination of rescue and relief operations. The Army's communication system served as an alternative communication channel as the public communication and mobile network was destroyed, and that enabled effective coordination of the disaster operations.

Emergency medical services and healthcare within few hours of the disaster was critical to minimize deaths and disabilities. Preparedness of the Army personnel, especially the medical corps, readiness of inventory of essential medicines and medical supplies, logistics and supply chain, and evacuation of patients as a part of disaster management protocols effectively launched the search, rescue, and relief operations and mass casualty reduction. Continuous and regular training and drills of army personnel, health professionals, and the community in emergency rescue and relief operations are important measures. Emergency drill is a usual practice in the army, which maintains the competence levels of the army personnel. Similar training and drill in civil administration and public health systems in emergency protocols for rescue, relief, mass casualty management, and communication would prove very useful in effective disaster management to save lives and restore health of the people.( 2 – 4 )

Lessons learnt and recommendations

Natural disasters not only cause a large-scale displacement of population and loss of life, but also result in loss of property and agricultural crops leading to severe economic burden.( 3 – 6 ) In various studies,( 3 , 4 , 7 , 8 ) several shortcomings have been observed in disaster response, such as, delayed response, absence of early warning systems, lack of resources for mass evacuation, inadequate coordination among government departments, lack of standard operating procedures for rescue and relief, and lack of storage of essential medicines and supplies.

The disaster management operations by the Indian Army in the natural disaster offered several lessons to learn. The key lessons were:

• Response time is a critical attribute in effective disaster management. There was no delay in disaster response by the Indian Army. The rescue and relief operations could be started within 1 h of disaster. This was made possible as the Army had disaster and emergency preparedness plans and protocols in place; stocks of relief supplies and medicines as per standard lists were available; and periodic training and drill of the army personnel and medical corps was undertaken as a routine. The disaster response could be immediately activated.
• There is an important lesson to be learned by the civil administration and the public health system to have disaster preparedness plans in readiness with material and designated rescue officers and workers.
• Prompt activation of disaster management plan with proper command and coordination structure is critical. The Indian Army could effectively manage the disaster as it had standard disaster preparedness plans and training, and activated the system without any time lag. These included standard protocols for search, rescue, and evacuation and relief and rehabilitation. There are standard protocols for mass casualty management, inventory of essential medicines and medical supplies, and training of the army personnel.
• Hospitals have always been an important link in the chain of disaster response and are assuming greater importance as advanced pre-hospital care capabilities lead to improved survival-to-hospital rate.( 9 ) Role of hospitals in disaster preparedness, especially in mass casualty management, is important. Army Hospital, Leh emergency preparedness played a major role in casualty management and saving human lives while the civil district hospital had become dysfunctional due to damage caused by floods. The hospital was fully equipped with essential medicines and supplies, rescue and evacuation equipments, and command and communication systems.
• Standard protocols and disaster preparedness plans need to be prepared for the civil administration and the health systems with focus on Quick Response Teams inclusive of healthcare professionals, rescue personnel, fire-fighting squads, police detachments, ambulances, emergency care drugs, and equipments.( 10 ) These teams should be trained in a manner so that they can be activated and deployed within an hour following the disaster. “TRIAGE” has to be the basic working principle for such teams.
• Effective communication system is of paramount importance in coordination of rescue and relief operations. In the present case study, although the main network with the widest connectivity was extensively damaged and severely disrupted, the army's communication system along with the other private mobile network tided over the crisis. It took over 10 days for reactivation of the main mobile network through satellite communication system. Thus, it is crucial to establish the alternative communication system to handle such emergencies efficiently and effectively.( 2 , 11 )
• Disaster management is a multidisciplinary activity involving a number of departments/agencies spanning across all sectors of development.( 2 ) The National Disaster Management Authority of India, set up under National Disaster Management Act 2005,( 1 ) has developed disaster preparedness and emergency protocols. It would be imperative for the civil administration at the state and district levels in India to develop their disaster management plans using these protocols and guidelines.
• Health system's readiness plays important role in prompt and effective mass casualty management.( 2 ) Being a mountainous region, the Ladakh district has difficult access to healthcare, with only nine Primary Health Centers and 31 Health Sub-Centers.( 12 ) There is a need for strengthening health systems with focus on health services and health facility network and capacity building. More than that, primary healthcare needs to be augmented to provide emergency healthcare so that more and more lives can be saved.( 7 )
• Training is an integral part of capacity building, as trained personnel respond much better to different disasters and appreciate the need for preventive measures. Training of healthcare professionals in disaster management holds the key in successful activation and implementation of any disaster management plan. The Army has always had standard drills in all its establishments at regular intervals, which are periodically revised and updated. The civil administration and public health systems should regularly organize and conduct training of civil authorities and health professionals in order to be ready for action.( 1 – 4 )
• Building confidence of the public to avoid panic situation is critical. Community involvement and awareness generation, particularly that of the vulnerable segments of population and women, needs to be emphasized as necessary for sustainable disaster risk reduction. Increased public awareness is necessary to ensure an organized and calm approach to disaster management. Periodic mock drills and exercise in disaster management protocols in the general population can be very useful.( 1 , 3 , 4 )

Source of Support: Nil

Conflict of Interest: None declared.

Senator Jamaal Bowman

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FOLLOWING DECADES OF ADVOCACY, SCHUMER, GILLIBRAND, BOWMAN SECURE $88 MILLION IN FUNDING TO BEGIN CONSTRUCTION OF THE MAMARONECK FLOOD MITIGATION PROJECT; REPS SECURE GAME-CHANGING 100% FEDERAL SHARE, AFTER DECADES OF DEADLY STORMS, HUNDREDS OF MILLIONS IN DAMAGE, FINALLY PREVENTING FLOODS & SAVING

FOR IMMEDIATE RELEASE:

Thursday, January 20, 2022

Contact:   Allison Biasotti (Schumer),  202-224-7433

Contact: Elizabeth Landau (Gillibrand), 202-224-3873

Contact: Marcus Frias (Bowman),   [email protected]

FOLLOWING DECADES OF ADVOCACY, SCHUMER, GILLIBRAND, BOWMAN SECURE  $88 MILLION   IN FUNDING TO BEGIN CONSTRUCTION OF THE MAMARONECK FLOOD MITIGATION PROJECT ; REPS SECURE GAME-CHANGING 100% FEDERAL SHARE, AFTER DECADES OF DEADLY STORMS, HUNDREDS OF MILLIONS IN DAMAGE, FINALLY PREVENTING FLOODS & SAVING LIVES 

Mamaroneck and Sheldrake River Flood Risk Management Project Was Stalled For Years, Prompting Schumer To Make Multiple Visits, Direct Calls To Top Brass, And Gillibrand and Bowman To Make A Full Court Press To Break Fed Logjam 

Reps Say $88 Million Project Will Construct Flood Defenses For Westchester Community That Has Been Victim of Severe Flooding, Lost Lives & Suffered Hundreds of Millions In Damages Over Decades 

Reps: After Years Of Fighting, Mamaroneck Will Finally Move Forward With The Flood Protection It Deserves 

Following years of advocacy and a Schumer-convened visit to the Village of Mamaroneck to survey the hundreds of millions in damage caused by Hurricane Ida,  U.S. Senate Majority Leader Charles E. Schumer, U.S. Senator Kirsten Gillibrand, and U.S. Representative Jamaal Bowman,   Ed.D,  today announced that after years of fighting, the project being blocked  under the Trump administration , and multiple direct calls by Schumer   Gillibrand, and Bowman to top administration officials making the case for this project, the U.S. Army Corps of Engineers (USACE) has heeded their calls and will provide $88 million in funding for the final design and construction of the Mamaroneck and Sheldrake River Flood Risk Management Project. 

“After years of pressuring and pushing federal agencies, this wonderful news from the Army Corps and the OMB finally breaks the federal logjam on this vital project and frees up the vital 100% funding we secured to finally move to design and construction for the Mamaroneck and Sheldrake River flood prevention plan,”  said Senator Schumer . “I visited Mamaroneck the day after Hurricane Ida, another deadly storm in a pattern of far too many that devastated the community, and promised I would not stop fighting until Mamaroneck received the funding it desperately needed to protect its community. With today’s announcement, I am pleased to know that promises made are now promises kept. I thank the Army Corps of Engineers, Army Civil Works, and OMB for heeding my call to approve the Mamaroneck project and finally starting the process to protect and rebuild the community that has suffered for decades because of severe flooding. I will continue to fight tooth and nail to see this project through to completion to ensure Mamaroneck residents have the flood protections and peace of mind they deserve.”

“As New York continues to weather increasingly severe storms, the Mamaroneck and Sheldrake River Flood Risk Management Project will save lives, which is why I fought for its inclusion in the 2018 Water Resources Development Act when I was a member of the Senate Environment and Public Works Committee,”  said Senator Gillibrand.  “I visited Mamaroneck shortly after Hurricane Ida and saw firsthand the unprecedented devastation of the storm. I’m proud to have fought alongside Senator Schumer and Representative Bowman to overcome years of setbacks and secure this federal funding. I’ll keep doing everything I can to make sure the project is completed in order to protect the residents of Mamaroneck from future extreme weather events.”

“As we approach five months since Hurricane Ida devastated Mamaroneck, I am grateful that our relentless work to bring flood mitigation money into our community is finally happening,”  said Congressman Jamaal Bowman, Ed.D (NY-16) . “After the Hurricane, I spent extensive time talking with families, assisting small business owners, and engaging community members as they tried to pick up the pieces of their lives. I vowed that their decades-old pleas for help would not go unnoticed any longer. Last fall, we saw an opportunity to include nearly $3 billion in new funding for disaster relief and resilience in H.R. 5305 and then worked with the Biden Administration to ensure that Mamaroneck was prioritized in this effort. This $88 million comes directly from our work on H.R. 5305, and our deep collaboration and partnership. With this funding, our community can finally move forward with flood mitigation efforts in Mamaroneck in a meaningful way. Still, I’m fighting for more. This is just one step forward on our path to prevent flooding and save lives from storms like Hurricane Ida, which are happening more frequently and getting stronger every time. The reality is that many of our neighbors were forced to evacuate, had homes that were destroyed, and some are still living in temporary housing because not enough flood mitigation resources had been brought into our community in the past. Myself and Senators Schumer and Gillibrand are changing that. We will continue to work in collaboration with federal, state, and local community advocates to make sure that we address the critical needs and ongoing challenges that our residents continue to face.”

“When Hurricane Ida hit Mamaroneck, Senator Schumer was quick to call and say enough is enough on getting the funding needed for the construction of the Mamaroneck and Sheldrake River Flood Risk Management Project. We’d been fighting for years to get this done and we both agreed that everyone needed to come together to cut through the red tape once and for all,”  said Village of Mamaroneck Mayor Tom Murphy.  “24-hours later, Senator Schumer brought officials at every level of government to Mamaroneck to see the devastation firsthand. He promised collaboration, to help rebuild, and to use his position as Majority Leader to get the  $88 million in funding needed to start construction on the project. He kept that promise. I want to thank Senator Schumer for his legislative work and countless calls to top administration officials to get this across the finish line and also thank  Senator Gillibrand and Congressman Bowman for their tireless advocacy.”

“ No one has been a stronger advocate for the Mamaroneck residents impacted by flooding than Senator Schumer.  He knows the pain and the loss and that is why he worked tirelessly to get the funding needed for the construction of the Mamaroneck and Sheldrake River Flood Risk Management Project.   He, and our entire federal delegation, put the federal spotlight on a problem the people of Mamaroneck have had to endure for far too long. $88 million dollars is an unbelievable amount of money and I am confident we would not have received that money had we not had Senator Schumer fighting for us.  Thank you to Senator Schumer, Senator Gillibrand and Congressman Bowman for their tireless work. This money will not only save property – it will save lives,”  said Westchester County Executive George Latimer.

"I want to thank all of our federal officials, and especially Senator Schumer, for their persistent efforts in securing $88 million for the construction on the Mamaroneck and Sheldrake River Flood Risk Management Project. After community input in the design phase, this will allow the Army Corps of Engineers to finally break ground on this much-needed project at no cost to the local taxpayers to save lives and prevent hundreds of millions in damages and destruction like we saw during Hurricane Ida. I’m proud to have worked with Senator Schumer and others to get this done,”  said   New York State Senator Shelley Mayer.

Assemblyman Steve Otis, a long-time supporter of the project added,  “Today’s great news for Mamaroneck is possible due to the determination and responsiveness of Majority Leader Schumer, Senator Gillibrand and Congressman Bowman. They worked with state, county and local officials to make the case that the Mamaroneck flood project must go forward and have provided additional funding to protect local property taxpayers as well. We are all working together to get construction started in Mamaroneck.”  

“I am grateful to Majority Leader Schumer for seeing to it that such a critical and monumental flood mitigation project had federal funding in addition to federal engineering. While as a partner to the Village of Mamaroneck to share the burden of local costs, Westchester was committed, but it would have taken up the lion’s share of money set aside for countywide flood projects. Now there is no question that we will be able to fund all projects this year that are shovel ready,”  said Westchester County Legislator Catherine Parker.

Specifically, this $88 million in construction funding will be provided through the  Disaster Supplemental Appropriations Bill , which Schumer made sure included $1.5 billion in Army Corps construction funding for Ida-affected communities like the Village of Mamaroneck.  Importantly, the representatives explained, construction projects selected will be 100% federally funded instead of the usual 65/35 federal and non-federal cost share, taking the burden off the local taxpayer.

The representatives explained that the project, which is now set to begin its design phase in the coming months, will reduce flood risk for the Mamaroneck and Sheldrake River Basins and help protect residents and business owners by constructing retaining walls and a diversion culvert. The project will also enable the deepening and widening of river channels, structure elevation, and other critical infrastructure updates. Overall, the plan has been estimated to potentially reduce average annual damages by approximately 87% and help reduce the risk of loss of life.

Schumer specifically has a  long history  of advocating on behalf of flood prevention in the Mamaroneck community. As mentioned, last year,  following a personal call from the senator to Acting OMB Director , Schumer  secured $1.5 billion in disaster supplemental aid to fast track Ida-impacted Army Corps of Engineers (USACE) construction projects.  Schumer then  made a personal call to the newly confirmed Assistant Secretary of the Army for Civil Works, Michael Connor,  to demand the inclusion of the Mamaroneck and Sheldrake River Flood Risk Management Project (the Project) to the Disaster Relief Supplemental Appropriations Act, 2022 work plan.

The current Mamaroneck and Sheldrake River Flood Risk Management Project was first imagined in response to a 2007 Nor’easter storm, which produced record flooding in the Village of Mamaroneck, equivalent to a one percent flood event. Senator Schumer traveled to the area the day after the storm to personally survey the extent of the significant damage. The 2007 event caused over $50 million in damages and impacted over 50 percent of total structures within the study area. The storm resulted in floodwaters peaking on the Mamaroneck River in approximately four hours, and in approximately six hours on the Sheldrake River. As such, the evacuation time for approximately 19,000 residents in the Village of Mamaroneck was severely restricted and created a high-risk situation. Over 40 percent of Mamaroneck residents required evacuation assistance prior to floodwaters peaking, including a large population of children that attended a school located within the epicenter of the severe flooding.

Following this, in March of 2010, a Design Agreement was signed by the Army Corps, NYS Department of Conservation (NYSDEC), and Westchester County for a Pre Construction Engineering and Design study. During this time, severe flooding again occurred during Hurricanes Irene and Lee in 2011. The flooding extended several blocks on both sides of Mamaroneck Avenue. The repeated disasters, including shoreline flooding from Super Storm Sandy in 2012, caused extensive damage and severely impacted the local economy. Following a $4.7 million Schumer-secured study by the Army Corps, the project was recommended by the Chief of Engineers and Schumer successfully fought to authorize this project for construction in the 2018 America’s Water Infrastructure Act. However, in February of 2020 it was discovered that the Trump administration would not move forward with the construction of the project because of the Benefit-Cost Ratio used by OMB, sparking community concern and outrage.

Now, thanks to Senator Schumer’s advocacy to have the project prioritized, Mamaroneck’s project will be funded through the Disaster Relief Supplemental Appropriations Act, 2022.

A copy of  Schumer, Gillibrand, and Bowman’s original joint letter to then Acting Assistant Secretary of the Army for Civil Works Jamie Pinkham and Commanding General and Chief of Engineers, Lieutenant General Scott A. Spellmon appears below:

Dear Acting Assistant Secretary Pinkham and Lieutenant General Spellmon:

As you select and prioritize projects for funding from the Disaster Relief Supplemental Appropriations Act, 2022 (P.L. 117-43) (Disaster Supplemental), we write to express my utmost support for the Mamaroneck and Sheldrake Rivers Flood Risk Management Project and strongly urge its selection as a construction project for full funding.

Hurricane Ida caused historic flooding throughout the New York Metropolitan Area and one of the hardest-hit areas is the Village of Mamaroneck in Westchester County. The village experienced significant damage with up to 14 feet of water flooding homes, businesses, and roadways. In the aftermath of the storm, streets in the Village were impassable, while many residents, including children and the elderly, remained trapped in flood-damaged homes waiting for assistance from first responders and more than half of the Village lost power due to flooding. There were over 150 water rescues, 535 flooded homes, 1,000 people displaced, and 310 abandoned cars. The Village has reported over $18 M in damages and over $75 M in residential and commercial damage.

Alarmingly, Hurricane Ida, which came on the heels of Hurricane Henri, is not the first time that a storm has caused significant damage to the Village of Mamaroneck. In April of 2007, for example, a Nor’easter caused over $50 million in damages and impacted over 50 percent of total structures within the USACE Project Area. Over 40 percent of Mamaroneck residents needed evacuation assistance, including children attending school within the epicenter of the severe flooding.

At least two deaths have occurred as a result of flooding within the project area, and an additional death occurred in the village due to Ida. Three deaths from flooding are three deaths too many and the construction phase of this project must commence as soon as possible. No bureaucratic impediments, no red tape, including a lack of full funding, should come between the project and the work that must be done.

The Disaster Supplemental legislation included $3 billion in funding for construction projects, including $1.5 billion in states, including New York, with a major disaster declared due to Hurricane Ida pursuant to the Robert T. Stafford Disaster Relief and Emergency Assistance Act, and the ability to fund projects at full federal expense.

Congress passed the Disaster Supplemental precisely so that critical flood and storm damage protection projects such as the Mamaroneck project would not continue to languish, and real progress could be made to advance them to the construction phase. We now urge you to select and approve the Mamaroneck and Sheldrake Rivers Flood Risk Management Project for full funding.

Thank you for your time and attention to this matter. Should you have any questions, please do not hesitate to contact me or my staff.

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Urban flood risk assessment and mitigation with InVEST-UFRM model: a case study on Kolkata city, West Bengal state (India)

• Original Paper
• Published: 17 April 2023
• Volume 16 , article number  320 , ( 2023 )

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• Suddhasil Bose   ORCID: orcid.org/0000-0003-4836-7779 1 &
• Asis Mazumdar 1  

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A Correction to this article was published on 25 May 2023

This article has been updated

Urban flooding has become a widespread issue across the world over the last few decades, making it crucial for cities to prioritise the flood risk mitigation. Kolkata has been selected as the study area as this city is densely urbanised and waterlogging situation is frequent here. The main goal of this paper is to apply the Integrated Valuation of Ecosystem Services and Tradeoffs-Urban Flood Risk Mitigation (InVEST-UFRM) model for the city Kolkata to understand the flood-like situation after consecutive rainfall for 2 h with different rainfall depths and find possible mitigation measures. The result finds Kolkata is covered up with 75% impervious surface where more than 80% of the rain water transforms into runoff after 2 h of rainfall and northern portion of Kolkata is extremely vulnerable to flooding. About 47% flood volume increases by 71% with a change in rainfall depth. Open green spaces have the highest potentiality to retain rainfall. Average runoff retention capacity of watersheds reduces about 10% with increase in 50% increase in rainfall. Economic damage costs about 10 lakh rupees for the most vulnerable area of 5.45 km 2 from the study area with a rainfall depth of 47 mm in 2 h. Flood risk related mitigation measures that should be followed for the study area with three perspectives like precipitation parameter, excess runoff reduction and runoff retention measures. Application of this model for urban flood mitigation is comparatively easy to use and more approachable for any urban area.

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Change history, 25 may 2023.

A Correction to this paper has been published: https://doi.org/10.1007/s12517-023-11486-y

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Bose, S., Mazumdar, A. Urban flood risk assessment and mitigation with InVEST-UFRM model: a case study on Kolkata city, West Bengal state (India). Arab J Geosci 16 , 320 (2023). https://doi.org/10.1007/s12517-023-11412-2

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The latest on the paused Ala Wai Flood Risk Management project

Most of the weather around the state is back to its usual pattern of trade winds and windward and mauka showers. But heavy rains from the recent Kona low caused flooding in several areas — and headaches for local officials.

Honolulu Managing Director Mike Formby told HPR that intense rain is a reality that city planners, and residents, have to deal with.

"We made it through the last Kona storm with I think minimal impacts, which is good, but it's just a wake-up call to all of us, you know, as to what potentially is coming. And we have to have the ability, the financial ability to make improvements to our systems so that we're ahead of the curve," Formby said.

Flooding in Waikīkī caused closures on main thoroughfares like Kalākaua Avenue. Waikīkī is part of the larger Ala Wai Watershed that stretches from Makiki to Mānoa to Pālolo, mauka to makai.

The city has been working with the U.S. Army Corps of Engineers on the paused Ala Wai Flood Risk Management project . The 19-square-mile watershed houses thousands of residents, public and private schools, the University of Hawaiʻi, and much of the tourism industry.

Formby said that while the latest cost estimate of about $1.1 billion was already a challenge, the 2023 ruling in Ideker Farms v. United States has forced the Army Corps to reevaluate flood mitigation plans nationwide.

Thousands of miles from Hawaiʻi, farmers and landowners along the Missouri River successfully sued the federal government for damages after a Corps plan led to "government-induced flooding" and damaged crops.

"What it basically does is it says if you induce flooding, even if it's not annual or consistent, that flooding event requires the U.S. government to consider whether or not that's a taking under the U.S. Constitution, which requires payment to the landowner," Formby said. "And that's just going to drive up costs."

"What I really suspect is at some point Congress will have to act because I don't think Congress will be able to accept the Ideker result and the impact that it might have to flood mitigation projects," he said. "They're probably going to have to say, we have to plan for climate change, and we have to be able to afford the plans for climate change, and if this is what the court believes is required, then we need to somehow limit that."

Formby said the city is waiting for the Corps to look at new cost estimates in light of the Ideker decision.

"We may not have a project that is perfect in mitigating all risk, but any risk that we can mitigate, in light of the cost of these flood mitigation projects, is something that we need to evaluate and consider because we simply can't be in an environment where we live on an island, and we say, 'Sorry, we're financially unable to deal with climate change and the risk that it poses to our residents.' That's just unacceptable."

This interview aired on  The Conversation  on May 21, 2024. The Conversation airs weekdays at 11 a.m. on HPR-1. Sophia McCullough adapted this story for the web.

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FY 2024 Pre-Disaster Mitigation Congressionally Directed Spending

Available Funding

Eligibility

Requirements

Project List

More Resources

On March 23, 2024, President Biden signed into law Further Consolidated Appropriations Act, 2024 , authorizing funding for FEMA’s Hazard Mitigation Assistance Pre-Disaster Mitigation grant program.

About the Program

The  Pre-Disaster Mitigation grant program  makes federal funds available to state, local, tribal, and territorial governments to plan for and implement sustainable cost-effective measures. These mitigation efforts are designed to reduce the risk to individuals and property from future natural hazards, while also reducing reliance on federal funding from future disasters. This funding is offered in addition to funds provided through other FEMA grant programs for projects that will support growing mitigation needs nationwide.

Communities and Tribal Nations with projects identified for funding must submit an application for their grants in accordance with the Fiscal Year 2024 Pre-Disaster Mitigation Congressionally Directed Spending funding opportunities published on Grants.gov .

View the FY24 NOFO

View the FY24 "Congressionally Directed Spending" Fact Sheet

For FY 2024, the total amount of funds that are being made available to 110 congressionally directed projects will be $190,568,289 .

A non-federal cost share is required for all subapplications funded through the Pre-Disaster Mitigation grant program. The non-federal cost share may consist of cash, donated or third-party in-kind services, materials, or any combination thereof. The cost share information is as follows:

• Generally, the cost share is 75% federal and 25% non-federal cost share.
• Small impoverished communities are defined as having 3,000 or fewer individuals identified by the applicant that is economically disadvantaged, with residents having an average per capita annual income not exceeding 80% of the national per capita income.
• Federally recognized Tribal governments meeting the definition of a small, impoverished community that apply to FEMA directly as Applicants are eligible for a 90% federal cost share for their planning, project, and management costs subapplications.

Eligibility Requirements

Only states, territories, or federally recognized tribal governments identified by Congress in the Further Consolidated Appropriations Act, 2024 and enumerated in the accompanying Joint Explanatory Statement for Division C are identified in this Notice of Funding Opportunity (NOFO) and are eligible to apply.

Each state, territory or federally recognized tribal nation with a project identified in the Pre-Disaster Mitigation funding opportunity shall designate one agency to serve as the applicant for funding. Each applicant’s designated agency may submit only one Pre-Disaster Mitigation grant application to FEMA.

Local governments, including cities, townships, counties, special district governments, and tribal governments (including federally recognized tribes who choose to apply as subapplicants) that are identified in the funding opportunity are considered subapplicants and must submit subapplications to their state applicant agency. Any tribal government identified in the funding opportunity that chooses to apply as a subapplicant must submit its application through the appropriate state applicant agency. For more information, contact the appropriate State Hazard Mitigation Officer.

Applicants may apply for management costs of up to 10% of the total federal share of each project subaward to manage that specific project. If the applicant would like to apply for management costs, it must be deducted from the subrecipient’s joint explanatory statement amount, up to 10% per subapplication.

The recipient must report on the management costs per 2 Code of Federal Regulations 200 and the 2023 Hazard Mitigation Assistance (HMA) Program and Policy Guide . Funding appropriated for one project may only be used for that project. Applicant requests for RMC must be submitted in a separate management costs subgrant application in FEMA’s grant application system. Management costs are 100%federally funded. 

When applying for Hazard Mitigation Assistance funding, all programmatic requirements must be met. FEMA has listed several requirements below as a quick reference, but it is encouraged to refer to the funding opportunity for a full list of all requirements.

Build America, Buy America Act Requirement

The Build America, Buy America Act (BABAA) requires all federal agencies, including FEMA, to ensure that all federal financial assistance for infrastructure projects meets the Buy America preference that all iron and steel, manufactured products, and construction materials used in that infrastructure are manufactured in the United States.

When necessary, recipients and subrecipients may apply for, and FEMA may grant, a waiver from these requirements. A waiver may be granted if FEMA determines that:

• Applying the domestic content procurement preference would be inconsistent with the public interest.
• The types of iron, steel, manufactured products, or construction materials are not produced in the United States in sufficient and reasonably available quantities or of a satisfactory quality.
• The inclusion of iron, steel, manufactured products, or construction materials produced in the United States will increase the cost of the overall project by more than 25%.

For FEMA awards, FEMA’s Interim Policy on BABAA requirements and information on the process for requesting a waiver from the Buy America preference requirements can be found on FEMA’s website at  “Buy America” Preference in FEMA Financial Assistance Programs for Infrastructure .

Hazard Mitigation Plan Requirement

All applicants and subapplicants must have a FEMA-approved Hazard Mitigation Plan by the application deadline and at the time of the obligation of funds, unless the subapplicant is applying for a planning subgrant.

The mitigation projects submitted with the application must be consistent with the goals and objectives identified in the existing FEMA-approved Hazard Mitigation Plan. Interested applicants and subapplicants should contact their State Hazard Mitigation Officer for guidance if they do not have a FEMA-approved Hazard Mitigation Plan.

FEMA may grant an exception to the local hazard mitigation plan requirement in extraordinary circumstances, when adequate justification is provided. This exception must be requested with the subapplication. If this exception is granted, a local hazard mitigation plan must be approved by FEMA within 12 months of the award of the project subgrant to that community.

Cost Effectiveness

All applicants and subapplicants applying for mitigation projects must demonstrate the cost-effectiveness of the mitigation project through a Benefit-Cost Analysis or other documentation. The Benefit-Cost Analysis is the method of estimating the future benefits of a project compared to its cost. FEMA has created a Benefit-Cost Analysis Toolkit that must be used to determine project cost-effectiveness. Please use the Benefit-Cost Analysis Toolkit found on the FEMA website.

FEMA is also leveraging an alternative cost-effectiveness method that will modify the threshold for mitigation projects to be cost-effective under limited conditions. This has long been identified as a challenge by stakeholders to applying for funding. Subapplicants may submit a cost-effectiveness narrative, rather than a Benefit-Cost Analysis, for projects costing less than $1 million. Please reference the program support material found on the FEMA website.

Technical Feasibility and Effectiveness Requirements

Mitigation projects must be both feasible and effective at mitigating the risks of the hazard(s) for which the project was designed. A project’s feasibility is demonstrated through conformance with accepted engineering practices, established codes, standards, modeling techniques, or best practices. Effective mitigation measures must provide a long-term or permanent solution to a risk from a natural hazard.

Environmental Planning and Historic Preservation Requirement

All mitigation projects must comply with all applicable Environmental Planning and Historic Preservation laws, including the National Environmental Policy Act (NEPA) and related Department of Homeland Security and FEMA instructions and directives. FEMA encourages the use of other supporting guidance that can be used to ensure all environmental requirements, including the Hazard Mitigation Assistance Job Aids.

Application Submission and Funding Deadlines

To apply for funding made available to these Congressionally Directed Spending projects through the Pre-Disaster Mitigation program, applicants must adhere to the following application submission and funding deadlines:

Application Opening: May 24, 2024

Eligible applicants must apply for funding using the Mitigation eGrants system on the FEMA Grants Portal:  https://portal.fema.gov .

Application Submission Deadline: June 28, 2024, 5 p.m. ET

Applicants experiencing technical problems outside of their control must notify FEMA prior to the application deadline and within 48 hours after the applicant becomes aware of the issue.

FEMA will not review applications that are received after the deadline or consider these late applications for funding.

The application review process begins following the application submission deadline. FEMA will review subapplications submitted by each applicant to ensure all eligibility requirements have been met and there is compliance with the Hazard Mitigation Assistance Guidance.

Application Funding Deadline: Aug. 30, 2024

Period of Performance (POP):

• Start Date: Date of the recipient's federal award
• End Date: 36 months from the start date of the recipient's federal award

Pre-Disaster Mitigation Congressionally Directed Spending Projects

For Fiscal Year 2024, the total amount of funds that are being made available to 110 congressionally directed projects is $190,568,289.

Communities and Tribal Nations with projects identified for funding must submit an application for their grants in accordance with the Fiscal Year 2024 Pre-Disaster Mitigation Congressionally Directed Spending Projects funding opportunities published on Grants.gov .

FY 2024 PDM Grant Program Project List

Additional resources.

In addition to the funding opportunity published on  Grants.gov , FEMA encourages the following additional resources be used for assistance in applying for funding:

• Pre-Disaster Mitigation webpage
• Hazard Mitigation Assistance Guidance
• Hazard Mitigation Assistance Job Aids

General Questions

For general questions about Pre-Disaster Mitigation Congressionally Directed Spending, please contact the appropriate  State Hazard Mitigation Officer  or  FEMA regional office .

The Hazard Mitigation Assistance helpline is also available by telephone at (866) 222-3580.

eGrants System Questions

You can visit the Mitigation eGrants (MT eGrants) System Resources for reference guides and job aids to help submit your application.

For assistance with using the eGrants system to manage your existing PDM grants, please email or call 855-228-3362.

Other Questions

If you require further assistance after navigating the resources above, please contact FEMA by email at  [email protected] .