The Development Characterristics And Risk Assessment On The Jiachehe Debris Flow Of Dam And Reservoir Sites On Wudongde Hydropower Station

Wudongde hydropower station dam site of Jinsha River is located at the tracts of Panzhihua City to Pudu river of Luquan county which is at the boundary of Sichuan and Yunnan in southwest China, and the dam is at the mainstream of Jinsha river,being the most upstream level of the four hydropower cascade in planning and construction - Wudongde, Baihetan, Xiluodu and Xiangjiaba at the downstream of Jinsha River. The primary normal pool level of power station was 975m, total reservoir capacity was 74.05×109m3, of which the regulating storage was 2.615×109m3,and flood control capacity is 1.447×109m3; power station's installed capacity was 8700MW (12×725MW); power output was 3230MW, annual average generating capacity was 39.07 billion kW?h; the reservoir could flood four large navigation obstruction rapids, formating 200km-long's deep water channel,to create good conditions for the future development of the reservoir shipping and,together with the downstream cascade, be role of flood control for the Yangtze River combined with the Three Gorges Reservoir.The harm of debris flow on water resources and hydropower engineering facilities mainly behaves with following several aspects:First,it may directly destroy hydropower facilities and drains and block them,at the same time it will also threaten the power station or building construction area.Second,it may transport massive solid matter, accelerate siltation of solid matter of the reservoir, lessen the effective storage, decrease the flood control ability, reduce the power rate.Last,the solid matter of debris flow will enter the main river, causing river bed lifting,blocking power station's water intake,which will bring adverse effect for the water and electricity projects. Therefore, before the construction of Wudongde hydroelectric power station,we should have an intensive study on debris flow gullies of the dam area to provide reliable basis for the engineering construction and the disaster reduction hindrance.This article based on the result of'The monographic study of the Wudongde hydroelectric power station in Jinsha River', we are selecting Jiache River of the reservoir area this typical debris flow, trying to analyze and research its aspects such as growth characteristic, origin mechanism, dynamics characteristic and risk appraisal and so forth, through out the typical analysis to identify the common law to achieve the purpose of engineering practice.At first this paper introduced the geological background of the study area, described the debris flow gully's development features of Jiache river, including the overall landform features, gully characteristics and zoning ones, and gave a discrimination on its developmental stage, single-channel activity strength and their type; then analyzed the formation mechanism of debris flow by using matter resource as the leading reason, founding the formation mechanism mainly act as:collapse and slide of Madian river Group accumulation layers,to drive the , mainly in the horse shop Creek Group layers of Slump role, genesis of phyllite, schist and other metamorphic rock debris flow, the impact of human economic activities, geological structure and seismic effects and meteorological and hydrological effects. According to Jiache river debris flow gully, its own characteristics, we calculated parameters that could reflect the kinetics characteristics of debris flow by using appropriate method and empirical formula, to provide a basis for future prevention and treatment programs; finally we established a system of risk assessment of debris flow, debris flow risk assessment could be divided into three processes: first is the selection of evaluation, then the determination of weights of evaluation index, finally the establishment of evaluation method. According to the specific circumstances of this project and previous experience, this paper chose 14 evaluation factors, and identified two major factors, other factors for the secondary. Through the gray system analysis method and based on correlation degree of secondary factor with the major factor, we simplified evaluation factors from fourteen ones reduced to eleven ones, then introduced the concept of attribute reduction in rough set theory and reduced useless information, to simplify eleven assessment factors to six ones, the evaluation factor of 11 reduction to 6; as for weight calculation, we used combined weighting method of the correlation method combined with rough set theory, which also was a combination of subjective experience and objective data attributes. We obtained the subjective weights through the correlation method, and got the objective weight with the introduction of importance concept in rough set theory attributes, after we established the most optimal model to get the comprehensive weights which not only consider engineering properties, but also consider the data itself's attributes; then we established extension model, to get the risk degree of eleven debris flow gullies including Jiache river debris, and analyzed the accuracy of evaluation results as the example of Jiache river debris flow gully;at last we put forward recommendations on prevention and control.