ENGINEERING MANAGEMENT AND ITS EFFECT OF LARGE DEBRIS FLOW AT HONGCHUN VALLEY IN YINGXIU TOWN,WENCHUAN COUNTY

A large debris flow disaster was triggered by a heavy rainfall in Hongchun valley, Yingxiu town on August 14, 2010.The debris flow carried out a lot of loose sediments and the total amount is about 80.5104m3.This debris flow led to serious secondary disasters including Minjiang river was blocked, Yingxiu town was flooded, the 213 highway was interrupted, the roadbed and bridge pier of a ramp bridge was destroyed. According to survey, a large number of loose sediments was distributed in the groove before the disaster., the valley was clogged seriously. So the outbreak of debris flow was inevitable in the condition of strong rainfall. To prevent the occurrence of debris flow again, a detailed investigation was carried out around Hongchun valley. The results showed that there were still many loose sediments of about 310.14104m3.Among unstable reserves, the loose sediments were about 98.4104m3.Large-scale debris flow disasters were extremely easy to outbreak in condition of strong rainfall. This paper introduces the debris characteristics, and analyzes its risk and development trend. Furthermore, it formulates the management roadmap of debris flows and puts forward the concept of the whole basin comprehensive treatment. In order to control debris flow disaster happening again, reinforcing management and loose sediment retaining measures are carried out in the middle and upper reaches of the valley. Solid groove bed and platoon guide measures are constructed in the downstream. After the completion of project, during two heavy rainfalls in July and August, 2011,there was not any solid loose sediments into Minjiang river and the treatment project was fine, which can reflect that the whole basin comprehensive treatment design concept has good effect for preventing giant debris flow.