Role of rock dip angle in runoff and soil erosion processes on dip/anti-dip slopes in a karst trough valley

Due to the great difficulty of monitoring surface and underground runoff and sediment yield directly, the surface and underground hydrological processes associated with soil leakage loss in karst trough valleys remain unknown. The objective of this study was to analyse the role of the rock dip angle in the water and soil leakage loss processes, to assess the characteristics of surface and underground runoff and soil erosion and to investigate their conversion relationships using rainfall experiments. The results showed the following. i) At a steep rock dip angle (60 degrees), the underground runoff yield had a shorter stabilization time than the surface runoff yield and that the underground runoff coefficient of the dip slope exceeded 0.5. ii) The surface sediment yield could be divided into the suspended load and the bed load and the underground sediment yield included only the suspended load. On the anti-dip slope, the surface erosion modulus was 0.83-2.50 times the underground erosion modulus. iii) The surface and underground cumulative runoff was linearly correlated with the cumulative sediment yield. The rock dip angle had a significant quadratic relationship with the surface and underground runoff and sediment yield. These results improve the understanding of the surface-underground runoff and soil erosion processes and have significance for preventing water and soil leakage loss on the slopes of karst trough valleys.