Flood simulation and parameter calibration of small watershed in hilly area based on HEC-HMS model

The rivers in the hill area have a larger drop, and heavy rains are liable to form mountain floods. Flood calculation in small watershed is a key link in the prevention of flash floods. Taking the Xueye Lake basin in Laicheng District as the research object, HEC-HMS was used to establish the semi-distributed hydrological model of the hill basin to calculate the rainfall-runoff and flood routing process. Based on the historical flood elevations of three typical floods, the sub-basin parameters were calibrated using the trial-and-error method. According to the flow data of the basin outlet, the peak-weighted RMS error function was selected as the objective function, and the Nelder-Mead optimization algorithm was used to estimate the overall watershed parameters. Rainfall and flow data for two floods were used to verify model accuracy. The results show that the relative errors between peak discharge and runoff depth are less than 20%. The model has good applicability to the flood simulation of the Xueye Lake Basin and can play an actual role in the mountain flood warning forecast. The proposed lumped parameter calibration and modeling method can provide reference for flood simulation in other small basins.