The effect of karst system occurrence on flood peaks in small watersheds, southwest China

Abstract

Flooding at small basins is characterized by weak predictability, sudden onset, and rapid disaster formation, especially in karst areas. Therefore, an accurate flood simulation will be helpful for flood control and disaster reduction. In this study, the reservoir unit is added into the original HEC-HMS model to improve the model and analyze the stagnation of the runoff process in karst basins. Then, the HEC-HMS model before and after improvement is used to simulate floods in the Xiajia basin, a typical karst area in southwest China. Before improvement, the calibration result shows that the accuracy of 31 flood simulations is poor, and the qualified rate is only 38.71%. After improvement, the qualified rate increases to 51.61% during calibration, and the simulation accuracy is increased by 12.90%. Moreover, the qualified rate reaches 61.11% during validation, and the simulation accuracy is increased by 22.40%. The improved HEC-HMS model can be applied to flood simulations in the study area and the study results can provide useful insights for flood warning and management in karst areas.