A laboratory experimental analysis of overland flow production with different slope gradients

Experimental evidence of the relationship between soil gradient and production of surface runoff at the slope outlet is given under the initial conditions of approximately saturated soil. A laboratory slope 152 cm long, 122 cm wide and 78 cm deep was used. The soil tray was adjusted between 1° and 15°. An artificial rainfall generator producing rainfall rates between 10 mmh-1 and 20 mmh-1 was employed. It was found that, for a fixed rainfall rate, the slope gradient has a positive influence on the steady state discharge and that this influence becomes comparatively higher with decreasing the rainfall intensity. An overall analysis of the recession limb of the hydrographs suggests that the slope angle gives a significant contribution to surface water through the generation of an outflow of soil water under conditions of approximately saturated soil. The magnitude of this mechanism is independent of rainfall rate.