Surface Water Hydrology

Oral Abstract

Non-monotonic and spatial-temporal dynamic slope effects on soil erosion during rainfall-runoff processes

Wednesday, January 4
10:30 AM - 12:30 PM
Location: 7th Meeting Room

The slope effect on flow erosivity and soil erosion still remains a controversial issue. This theoretical framework explained and quantified the direct slope effect by coupling the modified Green-Ampt equation accounting for slope effect on infiltration, the 1D kinematic wave overland flow routing model, and the WEPP soil erosion model. The flow velocity, shear stress, interrill, and rill erosion amounts were calculated for 0-60° isotropic slopes with the same horizontal projective lengths. The results show that, for short duration rainfall events, the flow erosivity and erosion amounts exhibit a bell-shaped trend which first increase with slope gradient, and then decrease after a critical slope angle. The critical slope angles increase significantly or even vanish with increasing rainfall duration but are nearly independent of the slope projective length. The rainfall intensity and temporal patterns have great influences on the slope effect trend, while the soil erosion parameters, soil type, and hydraulic conductivity have minor impacts. Neglecting the slope effect on infiltration would generate smaller erosion amounts and reduce critical slope angles. The relative slope effect on soil erosion in physically-based model WEPP was compared to those in the empirical models USLE and RUSLE. The trends of relative slope effect were found quite different but the difference may diminish with increasing rainfall duration. Finally, relatively smaller critical slope angles could be obtained with the same slope length and the range of variation provides a possible explanation for the different critical slope angles reported in previous studies.

Songbai Wu

Wuhan University

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Non-monotonic and spatial-temporal dynamic slope effects on soil erosion during rainfall-runoff processes



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