Flood Risk Assessment of Thiruvananthapuram City, Kerala

Flood is one of the most dangerous and deadliest natural hazards in the world which devastates both life and economy to a very large extent. In Kerala, climate change induced floods are becoming an annual problem. In the midyear of 2018 and 2019, Thiruvananthapuram, the capital city of Kerala, witnessed heavy rainfall and strong winds which resulted in widespread damage in various parts of the City. Flood risk assessment study provides a comprehensive detail of geographic areas and elements that are vulnerable to the particular hazard. As far as Thiruvananthapuram is considered, most of the flood risk assessment studies available were found to be based only on a specific catchment or stream. This paper discusses the need of flood risk assessment study of Thiruvananthapuram City and also focuses on estimating the intensity of storm causing flood.  In this work, the major natural drains and the places prone to drainage concentration are delineated from Digital Elevation Model of the study area. The drainage map and land use map are prepared using ArcGIS and ERDAS software respectively. The hydraulic modeling is done using HEC-RAS software and simulations for different rainfall intensities are carried out to estimate the magnitude of flood and to identify the major flood prone areas in the City. This study presents a systematic methodology that can be adopted for flood risk assessment of urban cities, especially when there is less available data.