Dynamic analysis of flood risk using HEC-RAS hydraulic model (Case study: Shahinshahr River, Isfahan Province)

Dynamic analysis of flood risk using HEC-RAS hydraulic model (Case study: Shahinshahr River, Isfahan Province)AbstractFlooding is a natural phenomenon and the risk of it occurring in urban areas is a global issue. Rapid urbanization and climate change have increased the risk of urban flooding, causing massive infrastructure and human losses. The aim of this study is geomorphological zoning of Shahinshahr River flood risk. Therefore, the HEC_RAS numerical model was used to simulate the flood and The geometric data was processed in the GIS by the HEC–GEORAS extension. The return periods of 25, 50 and 100 years of catchment area as well as its physiographic characteristics including area, length of main stream, CN curve number, concentration time, latency in the watershed were entered into the HEC-HMS software. Accordingly, the output results of maximum flood discharge with different return periods were calculated whereby river pattern reflect three reaches. Finally, manning's roughness coefficient was calculated for each reach that the Manning roughness coefficient was calculated using the Coon method. The results of studies show that the flood zone in the 25-year return period of 0.948 (km2) in the 50-year return period of 1.13 and in the 100-year return period of 1.34 (km2) of lands along the Shahin river. In the last reaches, due to the reduction of the slope and the reduction of the flow velocity, the flood zone has become wider than other periods.