FLOOD RISK MAPPING FOR EAST RAPTI RIVER, NEPAL USING GIS AND HEC-RAS

Abstract

Nepal is vulnerable to different types of hazard such as landslides, floods, drought etc. Among 75 administrative districts of Nepal, Chitwan is one of highly populated and hard hit district by disasters. Particularly the settlements and agricultural lands situated in the vicinity of East Rapti River are vulnerable to floods. In flood of July 2002, more than 500 families were displaced and hundreds of hectares of crops and houses were destroyed. Recently flood risk mapping and floodplain zoning are emerging as effective tools to reduce the flood damages. In developed countries insurance companies are using flood risk maps extensively. However for developing countries like Nepal the methodologies for flood risk mapping are yet to be developed/learned and mastered. The intent of the present work is to develop the methodology for flood risk mapping and demonstrate its use for East Rapti river. The methodology for flood risk mapping combines the results of flood frequency analysis and HEC-RAS in GIS environment The results of this study show that use of HEC-RAS and GIS with combination of regional flood frequency analysis (using L-moments) gives a robust methodology for flood risk mapping.