Influence de la longueur de pente sur le ruissellement: rôle de la formation de rigoles et de croûtes de sédimentation

Laboratory experiments have been conducted in order to investigate if the relationship between slope length and Norton runoff volume per unit area could be explained by the corresponding erosion and deposition patterns occurring within the plots. A binary soi1 mixture, very susceptible to surface sealing, was tested on 2.39 m, 7.18 m and 17 m slopes under simulated rainfall intensities from 24.2 - 26 mm/h for a minimum of 200 min. Runoff volume per unit area was not related to slope length in a simple manner. Detailed analysis of percolation data revealed a complex pattern dominated by surface sealing, rill development, headcut incision and colluvial fan formation. Slope segments where rills and headcuts developed were characterized by high infiltration and percolation rates. On the other hand, slope segments completely covered by sealed interrill surfaces or where important depositional seals formed, showed reduced infiltration and percolation rates. These processes cari have compensating effects on runoff generation along a hillslope. Realistic hydrological models aiming at predicting overland flow discharge along hillslopes should be (partly) driven by an erosion/deposition model.status: publishe

Laboratory experiments on the influence of slope length on runoff, percolation and rill development

Experiments to test relationships between slope length, percolation, and runoff were carried out in a laboratory flume under simulated rainfall at intensities from 24·2‐26 mm h−1. A composite soil subject to sealing was mixed from a clay and a sand and tested on 2·39 m, 7·18 m, and 17 m slopes for a minimum of 200 min. Runoff discharge is not a simple function of rainfall excess and slope length but shows a complex pattern dominated by surface sealing, rill development and headcut incision. Rill development by concentrated surface wash conformed to established threshold hydraulic conditions, but subsequent headcut incision was necessary to breach the seal and significantly affect percolation/runoff ratios. Headcut evolution is complex, apparently reflecting hydraulic instability and possibly different stages in seal development. Headcut and rill incision shows a cyclic pattern interspersed with broad areas of sheetwash and colluvial deposition where percolation rates are very low. Copyright © 1989 John Wiley & Sons, Ltdstatus: publishe