Influence Mechanisms of Spatial Optimization of the “Terraced Fields‐Gully Land Reclamation Project ( GLRP )” Cascades on Erosion‐Transportation Processes in Watershed in the Loess Hilly‐Gully Region

ABSTRACT

Terraced fields and the Gully Land Reclamation Project (GLRP) are important soil and water conservation measures, widely constructed in China's Loess Plateau and other ecologically fragile areas in the world. However, under large‐scale governance scenarios, the impacts of the “terraced fields‐GLRP” cascade system on water and sediment processes in watersheds constitute a critical scientific issue that needs to be addressed for optimizing governance strategies under the context of high‐quality development of the Loess Plateau. To address this issue, this study developed a novel watershed solid‐scale physical model based on 3D scene reappearance. The spatial pattern of “terraced fields‐GLRP” significantly affected watershed runoff and sediment production. The study defined the coefficient (watershed erosion modulus reduction per unit area of terraced fields and GLRP) as their spatial layout control index, and proposed three deployment modes: series, parallel, and mixed. Under the series mode, the maximum watershed erosion reduction (86.25%) occurred when the relative layout area of terraced fields was 40%–50% and relative height 0.5 ~ 0.9; under the parallel mode, the maximum reduction (91.22%) was achieved at 40% relative terrace area; under the mixed mode, the maximum reduction (95.33%) was observed at 40% relative terrace area and 0.6–0.8 relative height. Watershed erosion remained stable when was 0.4–0.5, with an erosion growth inflection point at ≈ 0.5. The results of this study have important practical significance for the water and sediment source of Yellow River and optimization of soil and water conservation measures in highly managed small watershed in the world.