Hydrological response and soil detachment rate from dip/anti-dip slopes as a function of rock strata dip in karst valley revealed by rainfall simulations

Abstract

Rock dip angle plays a significant role in surface hydraulic characteristics and leads to different spatial distribution of water and soil loss in Karst Trough Valleys. In this study, the rock dip angle effect on the hydraulic characteristics and soil detachment rate on dip/anti-dip slopes was explored via rainfall simulations and a steel experimental flume. The rainfall intensities ranged from 30 to 90 mm·h−1, and the rock dip angles varied from 10° to 60°. The results revealed that i) surface runoff on the dip slope was higher than that on the anti-dip slope, whereas underground runoff presented opposite results. The 30° rock dip angle presented the critical flow velocity for the anti-dip slope, and the flow velocity reduced as the rock dip angle of the dip slope increased. ii) Laminar water flow occurred on the dip/anti-dip slope (Re was <500 in all cases). For the anti-dip slope, the Re value reduced by 3.53–89.79%, the Fr value reduced by 34.13–73.04%, and the f value increased by 61.07–93.78% compared with that of the dip slope. iii) A linear function model can describe the relationship between the soil detachment rate and hydrodynamic parameters (τ, w and E). It was found that w was the best of the hydrodynamic parameters to describe the soil detachment rate. These results could provide valuable information for establishing a national-scale empirical soil erosion model for Karst Trough Valley.