Impact of Digital Elevation Model on Rainfall-Runoff-Inundation modelling - A Case Study of Lower Kelani River Basin

Flood hazard is a natural, and predominant disaster experienced due to climate change and the reimbursement of flood damage would be very expensive. The Lower Kelani River Basin is predominant as a highly populated region and hub of commercial activities. This region is vulnerable and frequently affected by flooding. Therefore, flood modelling is essential in developing flood management alternatives. It is the predominant countermeasure for developing flood early warning systems and mapping flood hazards to mitigate and prevent flood damages. The accuracy of the flood modelling depends on topographic data. This study evaluates the effect of different Digital Elevation Model products with an equal resolution on Rainfall-Runoff-Inundation hydrological model using 3-arc resolution SRTM, ASTER, HydroSHEDS, and ALOS PALSAR Digital Elevation Models. The simulation of discharge, flood inundations, and water depths for the flood event in 2016 was carried out for the Lower Kelani River Basin using the Rainfall-Runoff-Inundation model with each Digital Elevation Model. Under the different DEM products with the 3-arc resolution, the RRI model using SRTM and ALOS PALSAR performed well for both flood inundation and water level simulation in the Lower Kelani River Basin for the extreme flood event in 2016.