Soil erosion characteristics of terraces under extreme rainstorm conditions

Abstract

With the intensification of climate change and the increased frequency of extreme weather events, terraces, as a traditional agricultural practice, are facing severe challenges. This study investigated the characteristics of soil erosion on terraces under extreme rainstorm conditions, the dominant controlling factors influencing soil erosion, and the relationships between these factors in the terrace area of Qiugou watershed on the Loess Plateau. Utilizing high‐precision digital elevation model (DEM) data acquired through field surveys and unmanned aerial vehicle (UAV) aerial photogrammetry, topographic and hydrological factors were extracted through visual interpretation and model simulations. High‐resolution analysis was carried out on terrace erosion types, soil erosion intensity and the relationships between topographic/hydrological factors and runoff generation/erosion processes during extreme rainstorms. The results indicate that the extreme rainstorm caused five primary forms of terrace damage in the Qiugou watershed: gully erosion, cave erosion, rill erosion, slumping/collapse and shallow landslides. Within the study area, the soil erosion intensity of terrace platform and terrace wall, including channelized erosion and gravitational erosion, were 3732.10 and 27 843.26 t/km ² , respectively. The sheet erosion intensities of terrace platform and terrace wall were 2898.56 and 20 143.02 t/km ² , respectively. Terrace wall is the primary source of soil erosion in terraces. New terraces suffered significantly more damage, with a soil erosion intensity 1.16 times higher than that of old terraces. Slope gradient emerged as the key factor controlling the terrace soil erosion intensity, which increased with steeper slopes (reaching a peak in the 30°–50° range). Management strategies should therefore prioritize areas with slopes between 30° and 50°, which are commonly distributed within terrace wall. Optimizing terrace design to reduce soil and water loss requires synergistic regulation by combining the LS factor (slope length and steepness factor) and specific catchment area.