Frequency Difference of Debris Flows in Moxi Basin, Southwestern China

Debris flow is one type of remarkable geomorphological hazards in mountain area. The primary objective of this study is to investigate the relationship between active fault and debris flow frequency (including high-frequency debris flow (HDF) and low-frequency debris flow (LDF)) in Moxi basin. The study area is a typical high mountain environment dominated by tectonic uplifting and glacier movement, where debris flow frequency shows a distinct difference and many debris flow fans occupy the valley bottom. Based on the field survey, literatures study and the interview with residents, this paper uses geographic information systems (GIS) techniques to outline their relation with fault, and analyse possible effects on their frequency differences. Results show that the spatial distribution, topographic characteristics of debris flow gully, return period and numbers of debris flow are mainly controlled by the Xianshuihe fault because of the tectonic uplift. The frequency difference between HDFs and LDFs is mainly controlled by the glacier distribution, because the glacier deposits act as the available loose debris in source area of debris flow.