The effect of slope length on sediment concentrations associated with side-slope erosion

Data from experiments where artificial rainfall was applied on side slopes associated with ridge-tillage in the field and short inclined surfaces in the laboratory were analyzed with respect to the effect of rainfall intensity and slope length on sediment concentrations associated with the flows from the side slopes. In both the field and laboratory experiments, sediment concentrations associated with side-slope erosion were linearly related to the intensity of the rain produced by the rainfall simulator over the range of slope length (150-600 mm) and gradient (5-30%) used in this study once the surface condition stabilized. In addition, sediment concentrations associated with flows from the side slopes were found to increase not only with slope gradient but also with slope length, particularly when side-slope gradients exceed 10%. Increases in side-slope erosion rate with slope length on these higher side-slope gradients have, in the past, been associated with the development of small rips, However, increases in sediment concentrations with slope length also occurred on the higher slope gradients when rilling did not take place. In this latter case, the effect may be the result of a change from erosion dominated by raindrop detachment and raindrop-induced flow transport (RD-RIFT) to erosion dominated by RD and flow transport (RD-FT).