Study on Landscape Patches Influencing Hillslope Erosion Processes and Flow Hydrodynamics in the Loess Plateau of Western Shanxi Province, China

Although vegetation restoration plays an important role in the management of surface runoff and soil erosion, the large-scale restoration of vegetation can increase water consumption and reduce surface water resources, thus affecting the health of river ecosystems. Therefore, vegetation restoration should aim to achieve a vegetation landscape pattern that optimizes protection of soil resources while limiting water consumption. This study established field runoff plots with different landscape patch types, including bare land, S-road patches, strip patches, grid patches, and random patches, as well as different quantities patches of 5, 10, 15, and 20. An artificial rainfall experiment was conducted to determine the effect of different vegetation patches in reducing runoff and sediment, and the relationship between the types and number of vegetation patches and hydrodynamic parameters. The results showed that the runoff yields of the four vegetation patch types decreased by 16.1–48.7% compared with that of bare land, whereas sediment yields decreased by 42.1–86.5%. In addition, the resistance coefficients of the poorly connected patch patterns, including strip patches, grid patches, and random patches, ranged between 0.2–1.17 times higher than that of the well-connected S-road patch pattern, and the stream power decreased by 33.3–50.7%. Under a set vegetation coverage rate, an increase in the number of vegetation patches resulted in a significant reduction in runoff velocity, runoff yield, and sediment yield, increases in surface roughness and flow resistance, and reductions in runoff shear force and stream power. Besides, the sensitivity of soil to erosion decreased with an increasing number of the patch in the vegetation landscape, whereas the sensitivities of patch combinations with poor connectivity were lower than those with good connectivity. The results of this study highlight the importance of vegetation patch type and quantity for control of soil erosion.