The Characteristic Of River-blocking Caused And Forecast Model Research Of Large-scale Debris Flows

After the Wenchuan earthquake, the number of mountain collapses and landslides triggered by the earthquake sharp increasing, triggering more numbers and threats of large debris flow disasters within the scope of Sichuan area, and causing serious social and economic loss.And the river blocking phenomenons caused by the outbreak of large debris flow are common occurance, different from plugging river events caused by landslides, the river blocking caused by debris flow has the characteristics of sudden outbreaking, and more relatively threat. The secondary disasters caused by debris flow blocking or blocking off the main is more harmful and more serious than the debris flow itself.Such as the Hongchun gully debris flow on August 13,2010, the Gaojia gully debris flow on July 3, 2011,and the Caopo Mozi gully debris flow on July 10, 2013 and so on.All of them are cause heavy losses to the road and dwellings.So analysising and predicting the large river-blocking debris flow in the study area is extremely urgent.Because of the complexity of the river-blocking mechanism caused by debris flow, making people have insufficient awareness and understanding of the river-blocking caused by debris flow; the outbreak of multiple large debris flows in research areas after the earthquake, supplying abundant natural samples to deepen this type debris flow study.This article get analysis and exploration below after collecting a large number of people’s research results、detailed field investigation and a large number of indoor complex operations:First of all, through analysising the detailed field investigation and the collected related data in the study area, discussing the distribution of space and time of the 23 large river-blocking type debris flow; And based on the formation after the debris flow into the river, classifying the type of river-blocking caused by debris flow, and summarizing the basic characteristics river-blocking cuased by debris flow.Secondly, through the detail analysis of the selected three typical debris flow blocking river incidents, combining with previous research results, summarizing the main influencing factors of river-blocking caused by debris flow; From the view of the debris flow itself, and through statistical analysis the common points of the river-blocking phenomenon caused by 23 large debris flow in the study area, concluding basic pattern of river-blocking caused by these large debris flows.Again, through discussing the previous research about run out volume forecast model of debris flow, and combining with the actual situation in the study area, using correlation analysis to determine the relative elevation difference and the source volume as predictive factor of debris flow, and fitting the run out volume forecast model of debris flow; In addition, throughstatistical calculations of the run out distance model based on the run out corner and fan corner of debris flow and the run out distance based on source quantity, analysing its applicability in the research area, and using the FLO-2d numerical simulation method, to simulation analysis the Gaojia valley and the Caopo Mozi valley, and further studying on the run out scale of river-blocking caused by large debris flow.Finally, from the inherent character of the debris flow itself and the main river characteristics these two aspects, choosing the discharge of debris flow、volume-weight and the longitudinal shrinking slope of valley chnnel, and the river discharge、volumeweight and longitudinal shrinking slope of riverbed wihch corresponding to debris flow; Based on the selected evaluation factors, and using nonlinear regression mathematical methods of matlab software to statistical analysis the river-blocking caused by large debris flow in the studied area, establishing the forecast model of river-blocking caused by large debris flow, to better targeted forecasting the possibility and degree of riverblocking caused by large debris flow, to provide reference of the future prediction and loss assessment of debis flow ultimate effect.