坡度阀值与坡面泥石流--以重庆市北碚区为例

通过对重庆市北碚区的 2 1个坡面泥石流的实地调查表明 ,坡度对坡面泥石流发生具有重要控制性作用。在对坡面泥石流流域大量原始坡度进行统计分析后发现 ,各坡面泥石流的坡度分布具有明显的正态分布特征 ,且平均坡度分布具有显著的规律。根据这一分布规律 ,将本区坡面泥石流发生的坡度阀值确定为三类 :第一类的坡面泥石流植被覆盖率高 ,远离居民区 ,人类影响活动微弱 ,坡度阀值为 32 4° ;第二类坡面泥石流无一例外均位于林地结合部 ,森林覆盖率很低 ,人类活动影响十分剧烈 ,坡度阀值为 2 7 3° ;第三类的两条坡面泥石流相邻 ,均位于观音峡峡谷地带 ,它们的发生完全受地形条件的控制 ,坡度阀值为 36 8°。本文从定量的角度阐述了坡度阀值与坡面泥石流发生的关系 ,为生态脆弱区的划分、工程建设、防灾减灾和政府决策提供服务

Critical Gradient and Debris Flow on Slope A Case Study in Beibei, Chongqing

The investigations of 21 debris flows on slopes in Beibei district, Chongqing reveal that the gradient is crucial to debris flow formation, We find that the distribution of gradients is the normal distribution, According to the distribution of the average gradients of the drainage areas,We make sure that the critical gradients can be classified into three kinds. The average of the first kind is 32.4 degrees. The debris flows belonged to the first kind of the critical gradients are apart from residential areas and human being' activities are feeble, and at the same time, their vegetation rates are higher. The average of the second kind of the critical gradients is 27.3 degrees. The debris flows belonged to the second kind of the critical gradients are located the combinations of woodlands and farmlands, and human being' activities are acute and the vegetation rates are lower. The average of the third kind of the critical gradients is 36.8 degrees. The debris flows belonged to the third kind of the critical gradients are in the Guan-yin gorge. They are controlled by the terrain condition. We have found the relationship between the crucial gradients and the debris flow on mountain slopes. It can afford services to the dividing ecological frailty sections, engineering construction, preventing and decreasing disasters, and the government decision-making.