基于DEM的黄土丘陵沟壑区流域地貌特征及侵蚀产沙尺度研究

Geomorphological Feature and Scale Effect on Sediment Yield and Soil Erosion in Hilly Loess Areas,North China

基于流域DEM,运用Arcinfo对流域的集水区进行划分,提取流域高程、坡度、不同级别的沟壑等信息,在EXCEL中对其进行分析处理,计算出不同集水区沟壑密度、平均坡度、流域相对高程等。对支沟、干沟两岸的地貌信息进行统计分析,发现岔巴沟右岸的平均坡度、相对高程分别比左岸大0.87°,2.28 m,蛇家沟右岸的平均坡度、相对高程分别比左岸大1.82°,4.86 m,支沟两岸的差异大于干沟。分别对毛沟,支沟、干沟的沟壑密度随面积的变化进行分析,发现沟壑密度随面积的增大,有可能增大,也有可能减小,变化情况与所提取沟壑的级别有关。结合相关的水沙资料、地貌信息,侵蚀产沙能量的变化情况,对产沙模数的空间尺度效应进行分析。分析发现,一般情况下产沙模数的大小与流域面积大小没有直接的关系,在沙源充足的流域主要取决于面积变化时,流域内所能提供侵蚀产沙能量的变化情况。

From the DEM with a resolution of 5 m, watershed length, mean elevation, mean slope angle, drainage density and relative height difference are derived. It is found that the mean slope angle on the right bank of the Chabagou creek is 0.87° higher than on the left bank, and the relative height difference on the right bank is 2.28 m higher than on the left. For the sub-creek, this observation is also made and the difference between the right and the left bank is more significant. An analysis about the drainage density reveals that the drainage density may increase or decrease with drainage area, and this variation is related to the order of the gully under consideration. Based on the observed data, scale effect on sediment yield is also examined. It shows that area-specific sediment yield has little correlation with drainage area and its variation largely depends on the energy supply by watershed geomorphologic system.