Field investigation and dynamic analysis for debris flow in weijia gully of beichuan county (china) after the wenchuan earthquake

Abstract

A great amount of mountain hazards were triggered by the Wenchuan earthquake, such as rock falls, avalanches, landslides, debris flows and dammed lakes. Heavy rain on 24th September 2008 initiated debris flows in Weijia Gully of Beichuan County, which resulted in serious damage to infrastructures and lifelines. In this paper, the debris ow was investigated and analyzed. The results show that solid loose materials, microtopography and rainfall are the main reason for the event. The total loose mass generated by the collapse and landslides reaches about 2.69×105 m3, which provides abundance material. The conditions of the surface water infiltration, runoff and flow concentration are changed by strong surface disturbance and large-scale destructive vegetation damage, which is beneficial to the formation of the erosion and flood peak. The rainfall was 272.7 mm from 23 to 24 September, 2008 in the study area, and the maximum rain reached 41 mm one hour. Velocity, peak discharge, sediment discharge and impulsive force were calculated. The results were compared with investigation, which provide reference for the design of debris flow protection.