Urban flooding is one of the major challenges that India is facing every year to which a solid so... more Urban flooding is one of the major challenges that India is facing every year to which a solid solution is not yet available. Rapid-growing urban areas are responsible for the ground sealing which affects the natural drainage system. As a result, all the rainwater is going to flow through drainage system. Most of the drainage network in the country is old and deteriorated that needs immediate attention. Proper design and maintenance of drainage system can solve the problem to a maximum extent. But one of the difficulties encountered in design of drainage network of urban area is unavailability of peak runoff data for shorter time intervals at most of the locations. In this study, the preliminary assessment of drainage discharge for Zone V area of Hyderabad City is carried out. Hourly precipitation data is disaggregated using artificial neural networks (ANN) in order to obtain sub-hourly data. Intensity duration frequency (IDF) curves are constructed using the disaggregated sub-hourl...
Surface imperviousness is vital basin parameter and plays a major role in watershed hydrology esp... more Surface imperviousness is vital basin parameter and plays a major role in watershed hydrology especially in an urban environment. Estimation of surface imperviousness is crucial but tedious task in urban watershed modelling as urban land use changes very frequently. The challenge encountered in calculating surface imperviousness is the need for a simple and effective approach to the characterize impervious surfaces in the watershed without much error. Detailed land use land cover maps form a great source of information for hydrologic analysis. Recent advancements in technology have brought us the benefits of aerial photography and access to high-resolution satellite imagery. The present study highlights a methodology to extract surface imperviousness of an area by processing high-resolution satellite imagery and developing land use land cover map. Densely urbanized of part of Hyderabad city (Zone-XIII) being one of the critical flood-prone zone is picked in this study to extract sur...
Uncontrolled urbanization and climate change play a significant role in urban flooding. The condi... more Uncontrolled urbanization and climate change play a significant role in urban flooding. The condition in which rainfall excess exceeds the drainage capacity of storm water drains is called urban flooding. Urbanization disrupts the natural water balance by increasing impervious areas and reduction in infiltration. This increases runoff from urban catchments and leads to higher flood peaks even for short-duration low-intensity rainfall. Such flash floods significantly increase the expenses on mitigation efforts owing to their destructive nature. Urban flood management is one of the important topics of concern as frequent disasters are happening in almost all the urban areas. This is the indication of poor storm water management in urban areas particularly in developing countries like India. Thus, to improve the situation proper storm water drains and sewage network need to be planned and installed considering present land use pattern and probable future development. Present study focuses on the simulation of critical storm event for analysing drainage capacity for part of Hyderabad city (Zone XII). This study area is the most flooded catchment in Hyderabad, and it is ranked as priority number 1 in urban flooding. The drainage network exists in certain parts of the study area. Rainfall data is collected from the Indian Meteorological Department (IMD), and extreme rainfall events are found out. The response of the catchment to the extreme rainfall is modelled using HEC-HMS and HEC-Geo HMS. The simulated model gives a peak discharge of 590.5 m3/s at the outlet (Hussain Sagar Lake) for the August 2008 rainfall event having 221.4 mm precipitation for the duration of 34 h.
Abstract Climate change and urbanization are two major ongoing process worldwide and in past few ... more Abstract Climate change and urbanization are two major ongoing process worldwide and in past few years their impact on ground started becoming visible as increased events of intense rainfall and urban floods. Rapidly growing urban areas are liable to greater risk of climate change. Fine-scale rainfall forms the most important input to achieve greater accuracy in urban flood model simulation results. The major concern with modeling urban floods, particularly in developing countries like India is the unavailability of fine-scale rainfall data. This explains the need for developing a methodology to disaggregate large scale precipitation data into a fine-scale interval of time. A statistical rainfall disaggregation method is employed to scale down IDF parameters under climate change conditions. Synthetic rainfall hyetographs are developed from scaled IDF values and used as input to simulate the 1D 2D urban flood model. In this study, we used the combination of flow velocity (V), inundation depth (D), and the product (D × V) framed to quantify the flood-hazard for part of Hyderabad, India. The flood vulnerability produced by the hydraulic model is analysed and matched with the 2016 flooding event. The methodology implemented here produced acceptable results and hence evidences to be a reliable approach in an urban setting.
Flood is the most common natural disaster upsetting the highest population of the world. In recen... more Flood is the most common natural disaster upsetting the highest population of the world. In recent times, severe floods in urban areas are occurring more frequently owing to uncontrolled urbanization and climate change and it will continue to grow in upcoming years. Prevention of such events is not possible but with advancement of technology, flood-vulnerable areas can be identified through 2-D modeling of critical rainfall events. The difficulty associated with urban floods is unpredictable flow conditions in urban environment due to rapid alterations in topography and unavailability of extensive raw dataset. Thus, modeling of urban floods becomes a complex process. A vast number of numerical models have evolved over the past few years which are capable of flood mapping; most of them are commercial, rigorous and need extensive dataset to generate precise results. This paper presents a simple sophisticated approach to analyze extreme rainfall events based on past critical events and synthetic hyetographs developed from IDF curves for a part of Hyderabad, India. HEC-RAS, a freely available 2-D hydraulic model with integration to GIS is used to generate depth of flood inundation over underlying terrain and risk maps of flood inundation are developed for different rainfall scenarios. The model results identify 17% of total area is liable to floods out of which 9% area indicates high risk, 52% area shows medium risk and remaining 35% area falls under low risk of flooding. Urban floods • Hydraulic modelling • Flood risk • Hyderabad city • HEC-RAS model * N. V. Umamahesh
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2018
Space for water is now becoming guiding principle of urban planning because urban flooding is the... more Space for water is now becoming guiding principle of urban planning because urban flooding is the major problem facing by most of the cities in India. Urban development in developing countries like India usually occurs with high population concentrating in small areas, with poor drainage conditions. People occupy floodplain areas in low flood years and when larger flood occurs it causes high damage. The origin for urban floods is floodplains encroachment and unplanned drainage systems. Complexities in the urban environment and drainage infrastructure have an inherent influence on surface runoff. This runoff generates urban flooding which poses challenges to modeling urban flood hazard and risk. As like in river flooding satellite images are not available for unban flooding scenario. So better modelling provides minimizing loss of life and property. The present study focuses on recognizing the highly effected areas which are liable to flooding when extreme rainfall occurs for part of Hyderabad city (Zone XIII). The entire Hyderabad city is divided into 16 zones and each zone having details of existing drain network. A coupled 1D-2D flood modelling approach is used to identify flood prone areas and develop flood inundation and flood risk maps. 1D model for pilot area is developed using storm water management model (SWMM) and coupled with 2D PCSWMM. A web based GIS platform INPPINS is used to geo reference the existing network details and exported to 1D SWMM model. The model is simulated for extreme flood event occurred in past. The simulation run results identifies overflowing drainage nodes and flood inundation maps and risk maps prepared. The flood risk maps identify the low lying areas which need immediate attention in case of emergency. The overflowing nodes suggest the need of improvement of drainage in the area to safely dispose of the storm water and minimize the flooding. Urban flood as a hazard, defined by is the exceedance probability of the potentially damaging flood situation in a given area with specified period of time. Urban areas are densely populated areas thus there will considerable infrastructure damage and economic loss due loss of business, production and opportunity. Again flooding of streets affects the traffic system and day-to-day life. Figure summarizes the impact of urban floods on society and environment.
Journal of The Institution of Engineers (India): Series A, 2018
Urban floods are self-invited disasters which are responsible for huge property loss and in some ... more Urban floods are self-invited disasters which are responsible for huge property loss and in some cases loss of lives, self-invited in the sense man's desire for more and more land, and uncontrolled infrastructure development is altering natural land use, land cover and stream flow paths. Thus, high-intensity rainfall for shorter time period is producing high peak runoff from altered/urbanized catchment. The urban flood events in India have been increasing in past few years, affecting major cities, and the frequency of floods continues to grow in future. It is beyond our capabilities to prevent these events from occurring; therefore, it is very important to develop a strategy to combat such events so that losses in terms of human lives and property can be minimized. This paper explains a framework developed for flood modeling on regional scale combining GIS with a rainfall-runoff model (HEC-HMS) and a hydrologic model (HEC-RAS). Hyderabad city of India is considered as a pilot study area as it is a region of frequent occurrences of severe flash floods. Three major flood events, viz. July 1989, August 2000 and August 2008, that occurred in Hyderabad are selected as cases to examine the modeling framework, and flood inundation maps are prepared representing area at risk and delineate the regions where the flooding is likely to occur. The study represents the importance of 2D modeling of flood problems to develop management strategies to tackle the probable future events by employing flood risk reduction measures.
Asian Journal of Engineering and Applied Technology, 2018
Urban floods are caused due to increase in population density, development of urban infrastructur... more Urban floods are caused due to increase in population density, development of urban infrastructure without paying due consideration to drainage aspects and increase in paved surfaces. Storm water modelling plays an important role in checking issues such as flash floods and urban water-quality problems. The SWMM (Storm Water Management Model) has been an effective tool for simulating floods in urban areas. In this study a SWMM model is developed to analyze drainage network for the campus of National Institute of Technology, Warangal in the city of Warangal, Telangana, India. The model is simulated for one real storm event and 2-year return period of interval 1-hour design storm intensity. Frequency analysis is performed using best fitted distribution i.e., Gumbel’s distribution for different return periods and the frequency values are used for development of IDF (intensity-duration-frequency) curves. Design storm intensity derived from IDF curves for different return periods is used ...
In the modern era, the development paradigm is inclined towards urban storm-water management and ... more In the modern era, the development paradigm is inclined towards urban storm-water management and population growth, urbanization, and climate change are the major concerns in the development. Sequential flooding in urban areas has become a major concern to the city planners and modelers. The role of storm-water modeling is vital to check flash floods and issues related to the quantity and quality of storm-water. EPA SWMM has proven an effective tool for particularly in urban watersheds to effective analysis, management, and design of drainage system network. This study presents a storm-water modeling approach in concern with flooding's in urbanized watersheds using EPA SWMM 5.1 model. Pune-Urban, the cultural capital of Maharashtra State is considered as study area model development and simulated using critical rainfall events in the past. GIS approach is engaged in data handling and preparation. The simulation results show that the available drainage is not capable to handle the extreme rain intensities and overwhelm with a splash of rainfall. The surcharge junctions are identified as J-3, J-9, J-11, and J-21. Thus to avoid/reduce the flooding due to surcharging, the model suggests increasing the drain size joining these junctions or provide an alternate arrangement to carry the excessive flows.
The present study looks into the Hyderabad urban floods of October 2020 from a geospatial perspec... more The present study looks into the Hyderabad urban floods of October 2020 from a geospatial perspective. The spatial extent and severity of the flooding event for a part of the urban catchment (Zone-12) of Hyderabad city are modelled using HEC-RAS 1D-2D considering 13 October 2020 rainfall event. The study compares the present flooding to the previous flooding incidence which impacted Hyderabad, almost a decade back on 24 August 2000. The study shows that rapid unplanned urbanization ignoring the regional and local hydrological landscape has aggravated the flooding severity. The study highlights the fact that rapid, uncontrolled urbanization (16.5% increase) over the last two decades have substantially influenced the urban hydrology producing higher flood volumes for comparatively small rainfall event. Thus regulating urbanization, providing enhanced drain capacity, rejuvenating the water bodies and streams is need of an hour to check and reduce the spatial flooding extent.
Urban flooding is one of the major challenges that India is facing every year to which a solid so... more Urban flooding is one of the major challenges that India is facing every year to which a solid solution is not yet available. Rapid-growing urban areas are responsible for the ground sealing which affects the natural drainage system. As a result, all the rainwater is going to flow through drainage system. Most of the drainage network in the country is old and deteriorated that needs immediate attention. Proper design and maintenance of drainage system can solve the problem to a maximum extent. But one of the difficulties encountered in design of drainage network of urban area is unavailability of peak runoff data for shorter time intervals at most of the locations. In this study, the preliminary assessment of drainage discharge for Zone V area of Hyderabad City is carried out. Hourly precipitation data is disaggregated using artificial neural networks (ANN) in order to obtain sub-hourly data. Intensity duration frequency (IDF) curves are constructed using the disaggregated sub-hourl...
Surface imperviousness is vital basin parameter and plays a major role in watershed hydrology esp... more Surface imperviousness is vital basin parameter and plays a major role in watershed hydrology especially in an urban environment. Estimation of surface imperviousness is crucial but tedious task in urban watershed modelling as urban land use changes very frequently. The challenge encountered in calculating surface imperviousness is the need for a simple and effective approach to the characterize impervious surfaces in the watershed without much error. Detailed land use land cover maps form a great source of information for hydrologic analysis. Recent advancements in technology have brought us the benefits of aerial photography and access to high-resolution satellite imagery. The present study highlights a methodology to extract surface imperviousness of an area by processing high-resolution satellite imagery and developing land use land cover map. Densely urbanized of part of Hyderabad city (Zone-XIII) being one of the critical flood-prone zone is picked in this study to extract sur...
Uncontrolled urbanization and climate change play a significant role in urban flooding. The condi... more Uncontrolled urbanization and climate change play a significant role in urban flooding. The condition in which rainfall excess exceeds the drainage capacity of storm water drains is called urban flooding. Urbanization disrupts the natural water balance by increasing impervious areas and reduction in infiltration. This increases runoff from urban catchments and leads to higher flood peaks even for short-duration low-intensity rainfall. Such flash floods significantly increase the expenses on mitigation efforts owing to their destructive nature. Urban flood management is one of the important topics of concern as frequent disasters are happening in almost all the urban areas. This is the indication of poor storm water management in urban areas particularly in developing countries like India. Thus, to improve the situation proper storm water drains and sewage network need to be planned and installed considering present land use pattern and probable future development. Present study focuses on the simulation of critical storm event for analysing drainage capacity for part of Hyderabad city (Zone XII). This study area is the most flooded catchment in Hyderabad, and it is ranked as priority number 1 in urban flooding. The drainage network exists in certain parts of the study area. Rainfall data is collected from the Indian Meteorological Department (IMD), and extreme rainfall events are found out. The response of the catchment to the extreme rainfall is modelled using HEC-HMS and HEC-Geo HMS. The simulated model gives a peak discharge of 590.5 m3/s at the outlet (Hussain Sagar Lake) for the August 2008 rainfall event having 221.4 mm precipitation for the duration of 34 h.
Abstract Climate change and urbanization are two major ongoing process worldwide and in past few ... more Abstract Climate change and urbanization are two major ongoing process worldwide and in past few years their impact on ground started becoming visible as increased events of intense rainfall and urban floods. Rapidly growing urban areas are liable to greater risk of climate change. Fine-scale rainfall forms the most important input to achieve greater accuracy in urban flood model simulation results. The major concern with modeling urban floods, particularly in developing countries like India is the unavailability of fine-scale rainfall data. This explains the need for developing a methodology to disaggregate large scale precipitation data into a fine-scale interval of time. A statistical rainfall disaggregation method is employed to scale down IDF parameters under climate change conditions. Synthetic rainfall hyetographs are developed from scaled IDF values and used as input to simulate the 1D 2D urban flood model. In this study, we used the combination of flow velocity (V), inundation depth (D), and the product (D × V) framed to quantify the flood-hazard for part of Hyderabad, India. The flood vulnerability produced by the hydraulic model is analysed and matched with the 2016 flooding event. The methodology implemented here produced acceptable results and hence evidences to be a reliable approach in an urban setting.
Flood is the most common natural disaster upsetting the highest population of the world. In recen... more Flood is the most common natural disaster upsetting the highest population of the world. In recent times, severe floods in urban areas are occurring more frequently owing to uncontrolled urbanization and climate change and it will continue to grow in upcoming years. Prevention of such events is not possible but with advancement of technology, flood-vulnerable areas can be identified through 2-D modeling of critical rainfall events. The difficulty associated with urban floods is unpredictable flow conditions in urban environment due to rapid alterations in topography and unavailability of extensive raw dataset. Thus, modeling of urban floods becomes a complex process. A vast number of numerical models have evolved over the past few years which are capable of flood mapping; most of them are commercial, rigorous and need extensive dataset to generate precise results. This paper presents a simple sophisticated approach to analyze extreme rainfall events based on past critical events and synthetic hyetographs developed from IDF curves for a part of Hyderabad, India. HEC-RAS, a freely available 2-D hydraulic model with integration to GIS is used to generate depth of flood inundation over underlying terrain and risk maps of flood inundation are developed for different rainfall scenarios. The model results identify 17% of total area is liable to floods out of which 9% area indicates high risk, 52% area shows medium risk and remaining 35% area falls under low risk of flooding. Urban floods • Hydraulic modelling • Flood risk • Hyderabad city • HEC-RAS model * N. V. Umamahesh
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2018
Space for water is now becoming guiding principle of urban planning because urban flooding is the... more Space for water is now becoming guiding principle of urban planning because urban flooding is the major problem facing by most of the cities in India. Urban development in developing countries like India usually occurs with high population concentrating in small areas, with poor drainage conditions. People occupy floodplain areas in low flood years and when larger flood occurs it causes high damage. The origin for urban floods is floodplains encroachment and unplanned drainage systems. Complexities in the urban environment and drainage infrastructure have an inherent influence on surface runoff. This runoff generates urban flooding which poses challenges to modeling urban flood hazard and risk. As like in river flooding satellite images are not available for unban flooding scenario. So better modelling provides minimizing loss of life and property. The present study focuses on recognizing the highly effected areas which are liable to flooding when extreme rainfall occurs for part of Hyderabad city (Zone XIII). The entire Hyderabad city is divided into 16 zones and each zone having details of existing drain network. A coupled 1D-2D flood modelling approach is used to identify flood prone areas and develop flood inundation and flood risk maps. 1D model for pilot area is developed using storm water management model (SWMM) and coupled with 2D PCSWMM. A web based GIS platform INPPINS is used to geo reference the existing network details and exported to 1D SWMM model. The model is simulated for extreme flood event occurred in past. The simulation run results identifies overflowing drainage nodes and flood inundation maps and risk maps prepared. The flood risk maps identify the low lying areas which need immediate attention in case of emergency. The overflowing nodes suggest the need of improvement of drainage in the area to safely dispose of the storm water and minimize the flooding. Urban flood as a hazard, defined by is the exceedance probability of the potentially damaging flood situation in a given area with specified period of time. Urban areas are densely populated areas thus there will considerable infrastructure damage and economic loss due loss of business, production and opportunity. Again flooding of streets affects the traffic system and day-to-day life. Figure summarizes the impact of urban floods on society and environment.
Journal of The Institution of Engineers (India): Series A, 2018
Urban floods are self-invited disasters which are responsible for huge property loss and in some ... more Urban floods are self-invited disasters which are responsible for huge property loss and in some cases loss of lives, self-invited in the sense man's desire for more and more land, and uncontrolled infrastructure development is altering natural land use, land cover and stream flow paths. Thus, high-intensity rainfall for shorter time period is producing high peak runoff from altered/urbanized catchment. The urban flood events in India have been increasing in past few years, affecting major cities, and the frequency of floods continues to grow in future. It is beyond our capabilities to prevent these events from occurring; therefore, it is very important to develop a strategy to combat such events so that losses in terms of human lives and property can be minimized. This paper explains a framework developed for flood modeling on regional scale combining GIS with a rainfall-runoff model (HEC-HMS) and a hydrologic model (HEC-RAS). Hyderabad city of India is considered as a pilot study area as it is a region of frequent occurrences of severe flash floods. Three major flood events, viz. July 1989, August 2000 and August 2008, that occurred in Hyderabad are selected as cases to examine the modeling framework, and flood inundation maps are prepared representing area at risk and delineate the regions where the flooding is likely to occur. The study represents the importance of 2D modeling of flood problems to develop management strategies to tackle the probable future events by employing flood risk reduction measures.
Asian Journal of Engineering and Applied Technology, 2018
Urban floods are caused due to increase in population density, development of urban infrastructur... more Urban floods are caused due to increase in population density, development of urban infrastructure without paying due consideration to drainage aspects and increase in paved surfaces. Storm water modelling plays an important role in checking issues such as flash floods and urban water-quality problems. The SWMM (Storm Water Management Model) has been an effective tool for simulating floods in urban areas. In this study a SWMM model is developed to analyze drainage network for the campus of National Institute of Technology, Warangal in the city of Warangal, Telangana, India. The model is simulated for one real storm event and 2-year return period of interval 1-hour design storm intensity. Frequency analysis is performed using best fitted distribution i.e., Gumbel’s distribution for different return periods and the frequency values are used for development of IDF (intensity-duration-frequency) curves. Design storm intensity derived from IDF curves for different return periods is used ...
In the modern era, the development paradigm is inclined towards urban storm-water management and ... more In the modern era, the development paradigm is inclined towards urban storm-water management and population growth, urbanization, and climate change are the major concerns in the development. Sequential flooding in urban areas has become a major concern to the city planners and modelers. The role of storm-water modeling is vital to check flash floods and issues related to the quantity and quality of storm-water. EPA SWMM has proven an effective tool for particularly in urban watersheds to effective analysis, management, and design of drainage system network. This study presents a storm-water modeling approach in concern with flooding's in urbanized watersheds using EPA SWMM 5.1 model. Pune-Urban, the cultural capital of Maharashtra State is considered as study area model development and simulated using critical rainfall events in the past. GIS approach is engaged in data handling and preparation. The simulation results show that the available drainage is not capable to handle the extreme rain intensities and overwhelm with a splash of rainfall. The surcharge junctions are identified as J-3, J-9, J-11, and J-21. Thus to avoid/reduce the flooding due to surcharging, the model suggests increasing the drain size joining these junctions or provide an alternate arrangement to carry the excessive flows.
The present study looks into the Hyderabad urban floods of October 2020 from a geospatial perspec... more The present study looks into the Hyderabad urban floods of October 2020 from a geospatial perspective. The spatial extent and severity of the flooding event for a part of the urban catchment (Zone-12) of Hyderabad city are modelled using HEC-RAS 1D-2D considering 13 October 2020 rainfall event. The study compares the present flooding to the previous flooding incidence which impacted Hyderabad, almost a decade back on 24 August 2000. The study shows that rapid unplanned urbanization ignoring the regional and local hydrological landscape has aggravated the flooding severity. The study highlights the fact that rapid, uncontrolled urbanization (16.5% increase) over the last two decades have substantially influenced the urban hydrology producing higher flood volumes for comparatively small rainfall event. Thus regulating urbanization, providing enhanced drain capacity, rejuvenating the water bodies and streams is need of an hour to check and reduce the spatial flooding extent.
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Papers by VINAY RANGARI