Floodplain Mapping and Management of Urban Catchment Using HEC-RAS: A Case Study of Hyderabad City

摘要

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.