Developmental features and evaluation of blocking dangers of big ditch debris flow in Tang jiashan Dammed Lake

摘要

Big Ditch is at the upstream side of Tang Jiashan. It was a mountain gully before the "5.12" earthquake, however due to the collapses and landslides after the earthquake, the extremely rich loose sources were formed, with all conditions of the occurrence of a debris flow. And it has become one of the serious potential dangers of geological disasters after Tang Jiashan dammed lake successful discharge, and it also controls the normal use of Tang Jiashan dammed lake. The article is through on-the-spot investigation, on the basis of identifying the distribution and stability of the groove loose source, and combines the devel- opmental situation of "6.14" debris flow, systematically analyzes the developmental and dynamic features of Big Ditch debris flow. In particular, it analyzes the possible size of the debris flow under the different rain frequencies, and it evaluates the possible dangers of the blocking size, duration and outburst forms. The re- suits of analysis were confirmed by the once in 100year debris flow on September 24, 2008.