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