Experimental Study on Relationship between Subsurface Flow and Erosion on Purple Soil Slope in Three Gorges Reservoir Region

摘要

A series of simulated rainfall experiments under the five different slope gradients (10°, 15°, 20°, 25°, 30°, 35°) and the three different rainfall intensities (1.Omm/min, 1.5mm/min, 1.8mm/min) were conducted on the purple soil runoff plot, which is 5.0 meters long, 1.5 meters width. The relationship between the subsurface flow and surface flow was discussed in this paper. The results show that the percentage of the subsur face runoff account for the total runoff is between 2.5%-29.2% under the experiments. Under the same slope gradient, the per centage of the subsurface runoff account for the total runoff with the rainfall intensity decreasing, under the similar rainfall intensity, the percentage of the subsurface runoff account for the total runoff increases with the slope gradient increasing. By analyzing the relationship between the erosion pattem and the percentage of the subsurface runoff, the result indicate that the surface runoff is not the only erosion dynamical force and the prevalent subsurface runoff contributes considerable effects in the progress of the slope erosion by analysis the sediment yielding in various experiments, especially in the steeper slope, erosion exhibit the landslide or debris flows. The amount of erosion caused by debris flow or landslide is larger than that the erosion causing by sheet erosion and rill erosion on slope. So, we should take much into account the erosion that causing by subsurface flow in the hamessing the purple soil slope ero sion in three gorges reservoir region.