Rock dip angle affects relationship between slope hydrodynamic characteristics and soil detachment capacity: Evidence from land-use patterns of inverse and bedding slopes in karst trough valley

Abstract

Unique geological conditions and irrational human activities have given rise to a highly serious issue of soil erosion in karst area. The soil detachment capacity (D_c) serves as a crucial indicator for comprehending and accurately predicting process-based soil erosion models, which is influenced by bedrock strata dip (BSD) modifying occurrence state and hydrodynamic characteristics on slopes. However, due to the combined effect of BSD and hydrodynamic characteristics on D_c, quantifying the impact and mechanisms of BSD and rock dip angle (RDA) on D_c in different land-use patterns of karst trough valley remains challenging. In this study, an indoor simulated scouring flume was used to examine the variation in D_c under two BSD conditions (bedding and inverse slope) and three RDA gradients (10°, 30°, and 60°), considering five land-use patterns (cropland, natural grassland, abandoned land, forestland, and shrubland) and three flow discharges (60, 80, and 100 L·min⁻¹). This study revealed that the flow pattern on the bedding slope exhibited a steeper inclination and higher turbulence than the inverse slope, accompanied by high hydrodynamic parameters and D_c values. Spatially, there was an increasing trend in the mean value of D_c, flow depth (FD), shear stress (SS), and stream power (SP) with increasing RDA, indicating that the influence of BSD on hydrodynamic characteristics was strengthened by the increasing RDA. Furthermore, crop-land exhibited a significantly higher D_c values and most of the soil properties compared to other land-use patterns, with natural grassland demonstrating the lowest value, illustrating that the altering land-use patterns can impact D_c through changes in soil properties. Moreover, the dominant contributor to D_c was found to be SOM at 35.4 %, with FL, WSA, SP, and RDA following in the order of decreasing contribution. A prediction model (NSE = 0.897, R² = 0.906, P < 0.01) was developed to quantify the impact of RDA, soil properties, and hydrodynamic characteristics on D_c in karst mountain regions. This study provides valuable insights into elucidating the impact of BSD and land use changes on D_c and offering scientific references for facilitating soil and water loss control in these areas.