Flow characteristics of different rainfall type debris flow based on the HEC-HMS model

In order to explore the characteristics of debris flow discharge under different rainfall patterns, the rainfall data of typical debris flow in Wenchuan earthquake zone were collected and generalized into three rainfall types: three peaks early-arrival type, three peak type and three peaks late-arrival type. By constructing the Gaojia gully watershed model with the HEC-HMS hydrological model and based on the results of clear water flow in the basin, the debris flow under different rainfall patterns was calculated by the rain-flood correction method. The results show that the peak clear water flow rates of the three peaks early-arrival type, three peaks type and three peaks late-arrival type were 33.5 m3/s, 41.5 m3/s and 45.8 m3/s, respectively. The peak flow of debris flow was 166.83 m3/s, 206.67 m3/s and 228.08 m3/s, respectively with the errors of -25.6%, -7.8% and 1.7%, respectively. The runoff of the three patterns of rainfall evolved linearly from the upstream to the gully mouth. As the peak value of rainfall delays its rate of evolution continues to increase, and the growth rate gradually decreases. Debris flow bursts before and after the peak rainfall, which is a rainfall-inducing debris flow. As the peak rainfall delays, the flow growth phase takes a longer time of 5.5 h, 6 h and 9 h, respectively. The recession phase requires a shorter time of 14.5 h, 8 h and 2.5 h, respectively. The results show that the model can provide technical support for debris flow researches in areas without detailed rainfall monitoring data.