Regulatory mechanism of slope water erosion by strip grass cover patterns

• The inhibitory effect of grass cover is limited when rainfall intensity reaches a certain value. • The optimal hydrodynamic parameter to describe soil erosion is runoff stream power. • The presence of grass cover reduces the erodibility of slope soils. • Strip grass cover alters the hydrodynamic mechanism of slope erosion. The inhibitory effects of vegetation on slope water erosion are well documented, but the mechanisms by which strip grass cover regulates runoff and erosion are not fully understood. To further clarify the regulatory mechanism of slope runoff and erosion with strip grass cover, this study examined six striped grass cover types (0%, 20%, 30%, 40%, 50%, and 60%) under various rainfall intensities (1.0, 1.33, 1.67, and 2.0 mm/min) and slopes (10°, 15°, 20°, and 25°) in an indoor simulated rainfall experiment. The results showed: (1) the strip grass cover pattern had a significant inhibitory effect on slope water erosion, and the average runoff rate and erosion rate of grass cover slopes were reduced by 20.7%-39.4% and 30.28%-90.5%, respectively, compared with bare slopes; (2) Runoff velocities were reduced by a factor of 0.45–0.63 on grass cover slopes compared to bare slopes, with both showing the following pattern: lower slope > middle slope > upper slope; (3) Throughout the rainfall test, the slope runoff was predominantly supercritical laminar flow, with increased grass cover leading to decreased shear stress and stream power, and increased resistance in slope runoff. Runoff power can be considered as the best hydrodynamic parameters for describing soil erosion; (4) Grass cover can influence erosion rates both directly through its own negative influence and indirectly by regulating slope runoff and its hydrodynamic properties and reducing the erodibility of the soil. The results of the study can deepen the understanding of runoff and erosion regulation mechanism of strip grass cover, and provide scientific basis for improving the theory of slope water erosion on the Loess Plateau.