Post-Shock Gravitational Erosion and Sediment Yield: A Case Study of Landscape Transformation along the Wenchuan–Yingxiu Section of the Minjiang River, Sichuan, China

In Wenchuan, China, which was severely affected by an M8.1 earthquake in 2008, the geomorphic process has been driven by gravitational erosion brought on by post-shock rockfalls and landslides. However, a process-based delineation of the post-shock landscape modification using quantitative methods employing mathematical modeling and control experiments has not yet been successfully undertaken. This is due to the areas’ substantial sediment yield and growing transportation capacity. This study looked into 31 minor watersheds along the Minjiang River’s Wenchuan–Yingxiu stretch. Additionally, a digital gully model based on multi-source remote sensing, Geographic Information System (GIS), Differential Intereferometric Synthetic Aperture Radar (D-InSAR), and amplitude tracking technology was created for the quantitative estimation of post-shock gravity erosion and sediment yield by comparison of three-dimensional topographical alternation (before and after the shock). Following regression analysis, a useful model for sediment yield estimation was suggested. The following conclusions were reached: (1) There was a considerable favorable effect between an angle of 50 and 70 degrees, and various geomorphological parameters had scale effects. Gravitational sediment yield modulus displayed a positive power function relationship with relative relief and surface fragmentation, but there was no clear correlation between the modulus and slope, relative relief, or surface fragmentation at the watershed scale; (2) Both the budget for post-shock geo-materials and the production of sediment from gravity erosion showed an annual trend of decline; (3) A 10–20-year active period would be recognized by gravity erosion.