Floodplain Mapping Using HEC-RAS and Lidar Data: A Case Study of Bistrica River (Vrbas River Basin in B&H)

Abstract

AbstractHydraulic modeling is an important element of establishing a robust flood forecasting framework. Simulation results from hydraulic models can be used to produce inundation maps that community officials or the general public can use to evaluate their flood risk.This paper elaborates numerical simulation of flow in natural watercourses. Numerical simulation was done for the Bistrica River (Vrbas River basin in Federation of B&H) at the length of the considered stream about 4 km from the mouth of the Vrbas River. The establishment, calibration and validation of the model was carried out in the HEC-RAS software package based on the available data and substrates. The determination of the resistance coefficient “n”was carried out based on help of similar experiences of previously modeled watercourses, on recommendation of known methods for determining the Manning coefficient of roughness and also onsite prospecting. In this way, a good match of the simulated water level was obtained with the measured data at the Bistrica water meter station. At the end the goal was to obtain flood hazard maps based on a calibrated and verified numerical model. Flood waves of return periods of 20, 50 and 100 years were considered. For these events, flood maps were obtained showing the distribution of water depths and velocities using the ArcGIS and HEC-GeoRAS software tools. For these events, especially for T = 50 and T = 100, the water flows out of the main bed and the floods coastal areas. The results of numerical modeling of the flow and simulation of flood waves for the Bistrica River of the different occurrence rank, using the HEC RAS model have shown that its application is quite justified and it can be used as a good tool in future activities related to flood forecasting and prevention.KeywordsFlood modelingHazard mapsVrbas river basinHEC RASHEC-GeoRAS