强震区泥石流物源演化指标选取及规律分析

Evolution Indexes Selecting and Laws analyzing of Debris Flow Source in Strong Earthquake Area

为探究强震区泥石流物源演化规律,选择物源数量、物源面积、物源密度、物源连接度、物源长轴长、物源形状系数作为量化指标。通过对多期高清遥感影像解译和统计获取以上指标数据,经过分析得出以下几点结论:四期影像解译物源面积分别为7.86 km^2,6.67 km^2,4.67 km^2,3.25 km^2,分别减少了15%,30%,30%;物源数量为1310处,1582处,1203处,1004处,物源数量分别增长了21%,-24%,-17%;震后物源数量、物源连接度、物源长轴长以先增加后减少形式进行演化,于2011年前后演化至最大值,随后逐渐减小,而物源面积呈逐渐减少趋势;结合演化趋势研究结果,将泥石流物源演化阶段划分为幼年期、青年期、壮年期、老年期4个阶段;震后坡面物源演化方式将由碎屑流、坡面流形式逐渐转化为沟道侵蚀为主,而沟道物源侵蚀方式将由前期揭底侵蚀和沟道两岸物源坍塌补给为主向后期以水力类下切侵蚀加深为主。研究成果对于丰富震区泥石流物源演化理论具有积极意义。

In order to explore the evolution laws of debris flow source in strong earthquake area,the quantity,area,density,connectivity,length and shape coefficient of source are selected as quantitative indexes.The basic data were obtained through the interpretations and statistics of multi-phase images.The following conclusions are obtained through the analysis.The source area of the four phase images interpretation are 7.86 km^2,6.67 km^2,4.67 km^2,and 3.25 km^2,respectively,with the decreases of 15%,30%,and 30%,respectively.The numbers of sources are 1310,1582,1203 and 1004,with the increases of 21%,-24%and-17%,respectively.After the earthquake,the numbers,connectivity and length of the source evolved in the form of increase firstly,and then decrease,which reached the maximum around 2011,but the area showed a decreasing trend.The evolution stage of source can be divided into four stages:infancy,youth,adulthood and old age by combining the previous research results and the evolution trend of indicators.After the earthquake,the evolution type of source on the slope will gradually change from the form of clastic flow and hill-slop flow to channel erosion,and the source erosion type is transformed from the early-stage revetment erosion and materials collapse supply on both sides of the channel to the deepened erosion by hydraulic downcutting in the later stage.These research results have positive significance for enriching the theory of debris flow source evolution in earthquake area.