How does slope gradient affect runoff and soil erosion on hillslopes?
Abstract
The slope effect on runoff and soil erosion on hilslopes remains a controversial issue. To examine the essential impact of slope gradient on infiltration, runoff and soil erosion, a theoretical framework has been developed. The first component of this framework is a modified Green-Ampt infiltration model that explicitly addresses the role of slope gradient in infiltration, a key element in the Hortonian runoff generation process. Runoff on hillslopes can thus be more accurately simulated with this improvement. Furthermore, by coupling this modified infiltration model with the 1D kinematic wave overland flow routing model and the WEPP soil erosion model, the slope effect on soil erosion can be investigated. Modeling results for the cumulative infiltration, cumulative runoff depth, flow velocity, shear stress, interrill and rill erosion amounts on isotropic slopes for a wide range of slope gradients were used to examine the role of slope gradient in the complex process. The results show that, under the condition of equal horizontal projective lengths so that all slopes receive the same amount of rainfall, infiltration increases with increasing slope gradients and runoff decreases. In addition, for short duration rainfall events, the flow erosivity and the amounts of erosion exhibit a bell-shaped non-linear trend which first increase with slope gradient, and then decrease after a critical slope angle. The critical slope angles changes substantially with rainfall intensity, duration, and patterns, but is nearly independent of the slope length and soil erosion parameters, soil type, and hydraulic conductivity. The results of this study provide useful knowledge for understanding the fundamental mechanisms of the hillslope hydrology and erosion processes, and for modeling hillslope dynamics.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMEP33D1033C
- Keywords:
-
- 1815 Erosion;
- HYDROLOGYDE: 1824 Geomorphology: general;
- HYDROLOGYDE: 1862 Sediment transport;
- HYDROLOGY