基于运动波理论,在紫色土坡面径流侵蚀力和径流侵蚀能力的影响因素分析基础上,对三峡库区紫色土坡面土壤侵蚀的临界坡度进行了分析,分析结果表明:(1)坡面径流流量、水深和流速均随降雨强度的增大而增大,坡面径流流量和坡面径流水深随坡度的增大而减小,而流速随坡度的增大先增大再减小,在坡度为33.21°时达到最大值;(2)坡面径流侵蚀力随着降雨强度的增大而增大,而坡度对它的影响较为复杂,这个特定坡度随降雨强度和坡长的增大而减小,随坡面土壤颗粒粒径的增大而增大,对紫色土坡面而言,在37.14°-46.19°之间;(3)坡面径流侵蚀能力在临界坡度处达到最大值,临界坡度是一个变量,随降雨强度和坡长的增大而减小,随坡面土壤颗粒粒径的增大而增大,紫色土坡面径流侵蚀的临界坡度在35.93°-40.78°之间。
Theoretical analysis on runoff erosion of purple soil slope in the Three Gorges Reservoir area and its controlling factors was carried out based on the kinematic wave theory.The critical erosion gradient for the purple soil slope was analyzed based on the influencing factors of the runoff erosion force and capacity of purple soil slope.The results showed that:(1)The flux,depth and velocity of runoff increase with the increase of the rainfall density while the flux and depth of runoff decrease with the increase of the slope gradient,and the velocity of runoff increase with the increase of the slope gradient from 0 to 33.21 degrees and decrease with the increase of the slope gradient from 33.21 to 90 degrees.(2)The force of runoff erosion increases with the increase of the rainfall density,but the impact of slope gradient is complex.The slope gradient for the runoff erosion in purple soil slope has been estimated with its range from 37.14 to 46.19 degrees by using kinematic wave theory when the force of runoff erosion reaches th peak value.(3)The critical erosion gradient decreases with the increase of the rainfall density and slope length and increases with the increase of the soil particle size.The critical erosion gradient has been estimated with its range from 35.93 to 40.78 degrees by using kinematic wave theory.