Impact of earthquake-induced-landslides on hydrologic response of a steep mountainous catchment: a case study of the Wenchuan earthquake zone

Earthquake-induced-landslides will change the underlying surface conditions (topography, vegetation cover rate, etc.), which consequently may influence the hydrologic response and then change the flash flood risk. The Jianpinggou catchment, located in the Wenchuan earthquake (occurred in Sichuan, China, 2008) affected area, is selected as the study area. The distribution of the landslides is obtained from the remote sensing image data. The changes of topography are obtained from the comparisons among digital elevation models (DEMs) during different periods. A physical-based model, the integrated hydrology model (InHM), is used to simulate the hydrologic response before and after the landslide. The influence of the underlying surface conditions is then discussed based on the simulation results. The results reveal that landslides cause significant effects on the hydrologic response, and the impact is proportional to the proportion of surface flow in the total runoff. The effect of landslides on the runoff is insignificant at the outlet, but obvious in the local area. The larger the rainfall, the more visible the impact, and the impact of landslides will increase rapidly at the threshold of the runoff (the total rainfall of 235 mm in 6 h in the study area), but there is a limit with the further enlarged rainfall. The improved understanding of the impact of landslides on the hydrologic response provides valuable theoretical support for storm flood forecasting.