Prioritization Flood risk of Hydrologic Units (Case Study: Pole Shah Catchment)

Determining of flooding potential and prioritization of sub-catchments based on it, is one of the most important issues in the landuse planning studies. In this study flooding prioritization of sub-catchments in the Pole-Shah catchment, Kermanshah province, Iran was carried out. For this purpose, different data layers such as physiographic condition, climate, geology, soil, landuse, landcover and annual flood hydrograph of the study area were used. Then by checking the rainfall data and its related flood data, two events were selected for calibration and one event was selected for validation. SCS method was used for rainfall-runoff simulation. Curve Number method was used in HEC-HMS software for determining of initial losses. The model evaluation was conducted by Nash-Sutcliffe index. To determine the unit rainfall, the statistical distribution methods were used in SMADA software using statistics of 1998-2015 period. The results showed that model efficiency coefficient is positive for both events after calibration and rose to 0.872 and 0.173. In The validation process, based on the average adjusted of curve number and the initial losses, the efficiency ratio was 0.336 and peak flow error was 8 % that shows the accuracy of the model. The unit rainfall by 93 mm may leads to a 200 m3/s peak flow in the outlet. The results shows that sub-catchments located in the catchment outlet have a high flooding risk because of their geologic and land cover conditions; while sub-catchments located in the upstream have a low flooding risk.