Abstract:

Shaer Gully，an old debris flow gully，the first order right branch of Dadu River，is located in Jinchuan County，Sichuan Province，which is one of the seriously affected counties during “5.12” Earthquake.In order to study the earthquake's influence on debris flow gullies in affected areas during “5.12” Earthquake，we studied the characteristics and development trends of debris flow in Shaer Gully based on detailed field survey and investigation.The debris flows of this gully could be defined as median frequency，mediumlarge scale，higher viscosity，muddy and bouldery debris flows.The main characteristics of debris flows were as follows： (1)Rainstorm was main triggering condition；(2)It caused rapidly disasters and serious damages；(3)Main harming actions were destruction and burying.The amounts of loose materials had further increased in this gully due to the earthquake and reached 1300×104 m3 in volume，approximate 300×104 m3 of which could be involved in subsequent debris flows.Consequently this gully has already had the possibility of breaking out large scale debris flows.According to calculation results，the once total volume of debris flow exceeded 9×104 m3 and 13×104 m3 under the precipitation of 50 years cycle and 100 years cycle，respectively.From this study，we found that the earthquake had some influences on debris flow gullies in these affected areas，but it was not serious.Its development trends had no significant change.