Flood Inundation Modelling in Greater Colombo Region Using HEC-RAS 2D

Abstract

Floods and associated destructions occur frequently due to climate change, unplanned development activities and rapid urbanization of flood plains. Flood risk of the Colombo which is the business capital of Sri Lanka with high population and investments, has increased recently due to the flooding of the Kelani River. In this study, two-dimensional Hydraulic Engineering Centers' River Analysis System (HEC-RAS) is used to develop a flood inundation model for the Greater Colombo region. The model was calibrated and validated using the flood events in May 2016 and May 2017, respectively. The model simulates the flood discharge and inundation extent satisfactorily. The model is a valuable tool for flood inundation forecasting in the Greater Colombo region. Highlights: 1. Two-dimensional hydrodynamic model was developed using 2D HER-RAS for Greater Colombo region considering the Kelani River and canal network in and around the city, to compute flood inundation. 2. The model estimated the flood discharges and inundation extents during past storm events satisfactorily. 3. The developed model is a useful tool for flood inundation forecasting in the Greater Colombo region under anticipated storms announced by weather forecast.