Debris flows in meigu county of sichuan (sw china): geomorphology and hazards

Abstract

A torrential rainstorm on June 1, 2005 in Meigu county of Sichuan province, SW China, resulted in the generation of debris flows from two drainage basins. Map (1:50000 scale) of topography and depositing materials, coupled with the data from meteorological station and field investigation, are used to evaluate the geomorphology and hazard characteristics of debris flows. The return period of debris flows is 20 years and its magnitude is small-moderate scale. Rainstorm and hail with short duration and high intensity in the upper reaches of drainage basins are the triggering factor for debris flows. Unstable side slope in low-middle reaches and a large number of scattered materials in channels provide source materials for debris flows. Grain-size curves of debris flows are multiple peaks. The high clay content, boulder piling up boulder, mud crack show that the debris flows are viscous. Debris flows occurred abruptly, 9 local residents were killed or missed, 8 were injured and great property was lost