Flood hazard mapping using the CCHE2D numerical model in the Hable-rud River-a reach located downstream of Bone-Kuh Village

In this research, given the condition of the Hable-rud River in a reach placed downstream of Bone-Kuh Village in Semnan Province, probability of flood occurrence and consequent damages, and also the exposure of various valuable elements of the floodplain to floods, using the CCHE2D numerical model, the flood hazard map was created for the 100-year return period as the base-flood. This research aims to map the base-flood zone and to identify the areas exposed to the flood in line with flood risk management.  For this purpose, the required data for modeling, such as a large-scale topography map were prepared and flow characteristics (velocity and depth) were measured in the study area. Consequently, the computational grid has been assigned. To achieve the best simulation, the model calibration was performed by choosing the superior network and by changing the roughness coefficient. To evaluate the simulation, the model estimations were compared with the measured values for velocity and flow depth in three sections along the reach. For flow velocity, the model error was estimated to be 0.084 and 7.41% considering the RMSE and the MAE criteria, respectively. Given the flood hazard map created for the return period of 100-year, it is predicted that the area which is covered by orchards, croplands, and rangelands will be inundated with the base flood. Also, the analysis shows that about 18% of the study area is located in the moderate to high flood risk classes.  Providing the findings of this research to the local communities in the form of the map illustrating the position of various land uses on the 100-year return period flood zone can be very effective in enhancing awareness and flood risk perception of them.