紫色土坡面壤中流形成与坡面侵蚀产沙关系试验研究

Experimental Study on Runoff and Sediment Yield Characteristics on Purple Soil Slope

采用人工模拟降雨法,在长5.0 m、宽1.5 m、6个不同坡度(10°,15°,20°,25°,30°,35°)的径流小区上,通过3个不同降雨强度(1.0,1.5,1.8 mm/min),对紫色土坡面产流形式及侵蚀产沙关系进行了模拟试验研究。结果表明:紫色土坡面总径流主要由地表径流和壤中流两种形式组成,地表径流和壤中流在总降雨量中的比例随雨强和坡度的不同而发生变化,在相同坡度情况下,壤中流占总降雨量的比例随雨强的减小而增大,在雨强相似的条件下,壤中流占总降雨量的比例随坡度的增大而增大。普遍存在的壤中流在土壤侵蚀尤其是重力侵蚀中起到了相当重要的促发作用,甚至由壤中流促发的侵蚀量要远远高于片蚀、沟蚀等坡面侵蚀形式,这与以往研究表明的长江流域坡面侵蚀以面蚀为主的结论有所不同。

For studying the runoff characteristics of purple soil slopes in Three Gorges reservior region, a series of simulated rainfall experiments under the different gradients（10°, 15°, 20°, 25°, 30°, 35°）and the different rainfall intensities（1.0 mm/min, 1.5 mm/min, 1.8 mm/min） were conducted on a test zone plot with 5.0 meters long and 1.5 meters width. The erosion characteristics, sediment yield mode, runoff generation process and the percentages of the surface runoff and the subsurface runoff accounting for the total precipitation are discussed in this paper. The results show as follows： The runoff generation mode belongs to saturated runoff. The percentages of the surface runoff and the subsurface runoff holding the total precipitation rainfall vary with the different rainfall intensities and the gradients. Under the same slope gradient, the percentage of the subsurface runoff possessing the total precipitation increases with the rainfall intensity decrease; under the similar rainfall intensity, the percentage of the subsurface runoff occupying the total precipitation rainfall increases with the slope gradient increase. The subsurface runoff is not only the dynamical erosion force but also takes a considerable effect in the progress of the slope erosion by analyzing the sediment yielding in various experiments, especially in the steeper slope, the erosion forming a debris flow so as to lead to gravity erosion because of the abundant subsurface runoff. The amount of erosion caused by the subsurface runoff is larger than that caused by sheet erosion and rill erosion on slope. This result is different from that gained by previous, so account should be taken much into the erosion caused by subsurface flow in the harnessing the slope erosion.