Research On Magnitude And Runout Distance Of Of Debris-flows In Strong Earthquake Area

On 14 Augest 2010, a total of 21 debris-flows were triggered by heavy rainfall around the town of Yinxiu, located at the epicentre of the Wenchuan earthquake. One of debris-flows originated from the Hongchun gully was truly catastrophic. It traveled across Mingjiang river and produced a debris-dam, which then changed the course of the river and resulted in the flooding of newly reconstructed Yinxiu town.Rainstorm-induced debris ?ows were remobilized from landslide debris triggered by the May 12, 2008 Wenchuan earthquake. The resulting debris ?ows had very high energy and transported large amounts of loose material in the Meizoseismal area. Their peak discharge reached levels several times normal, notably during the rainstorm-induced debris ?ows of September 14, 2010 in the epicenter area, in the Wenchuan earthquake area. This phenomenon was due to the presence of large amounts of loose material deposited by the earthquake-induced landslides in the debris-?ow catchments and provides a rich source of material for debris flow. Therefore. errors will occur if existing debris-?ow runout models are employed to assess the hazardous zones connected with debris ?ows in earthquake-affected areas. For this reason, it is necessary to establish an appropriate model to predict the possible debris-?ow magnitude and runout distance on the alluvial fans after the Wenchuan earthquake in the Meizoseismal area. Debris ?ows that is beside theYingxiu town and Longchi town of the Wenchuan earthquake Meizoseismal area triggered by the August 14 rainstorm were selected .Investigated using high-resolution aerial photography and ETM imagery to extract a set of landslide deposit volumes in the debris-?ow catchment areas and also the dimensions of the deposition fans. There are not a unified calculation for Thickness estimated of regional landslide domestic at home and abroad, we collected the sample of landslide within the catchment of debris fiows in the study area, using multiple regression techniques, and then computer programming, curve fitting of sample data obtained in the study area Landslide source area - volume curve, the formula could be used to calculate the volume of the basin single landslide.using the method of combining the investigation and the model calculations to obtain the thickness of the alluvial fan-site, the model is triangular cosine formula. using the topographic data of 1:5 million to obtain the topography of debris flow of study area.This paper describes the process of debris-flow initiation and deposition in the study areas and presents field observations on the roles of rainfall duration, sediment supply, and basin topography for influencing the location and abundance of debris-flow activity.The assessment of the debris ?ow hazard potential has to rely on semi-quantitative methods. Due to the complexity of the debris-?ow process, numerical simulation models of debris ?ows are still limited with regard to practical applications.Thus, an overview is given of empirical relationships that can be used to estimate the most important parameters of debris-?ow behavior. In a possible procedure( multivariate regression analysis ),an assessment of a maximum debris-?ow volume may be followed by estimates of the runout distance on the fan.The applicability of several empirical equations is compared with available field and laboratory data, and scaling considerations are used to discuss the variability of the parameters over a large range of values used the laboratory data of Qingping stduyarea in the Meizoseismal area.The validation showed that the established model was suitable for the prediction of the debris-?ow magnitude and runout distance in the Wenchuan earthquake area. the prediction model does not apply to all the debris-?ow. In the text, the applicability of the prediction models was limited by the different of the valley characteristics. The results of the study will help authorities select safe sites for rehabilitation and relocation in the future and can also be used as an important basis for debris-?ow risk management. Also regard to the application of the presented relationships by practicing engineers, apart from advocating field reconnaissance and searching for historic events wherever possible.