A FIELD-STUDY ON TOPOGRAPHICAL AND TOPSOIL EFFECTS ON RUNOFF GENERATION

Runoff production was studied on small plots under natural meteorological conditions to evaluate the effects of slope, length and topsoil characteristics. The data show that slope has in many cases a significant negative effect of runoff yield: this result can partly be explained by the conceptual model of POESEN (1984). However, differential soil cracking also plays a major role, even on the loamy soils under study. On the plateau site runoff yield is generally positively related to plot length, which is due to the differentiation of crust characteristics with distance downslope. This phenomenon does not occur on steep slopes, so that runoff yield is here lower on longer plots. This implies that the slope effect may even be more important on larger surfaces.