Land Degeneration due to Water Infiltration and Sub-Erosion: A Case Study of Soil Slope Failure at the National Geological Park of Qian-an Mud Forest, China

Sustainable development of the natural landscape has received an increasing attention worldwide. Identifying the causes of land degradation is the primary condition for adopting appropriate methods to preserve degraded landscapes. The National Geological Park of Qian-an mud forest in China is facing widespread land degradation, which not only threatens landscape development but also endangers many households and farmlands. Using the park as a research object, we identified the types of slope failure and the factors that contribute to their occurrence. During June 2017, a detailed field survey conducted in a representative area of the studied region found two main types of slope failure: soil cave piping and vertical collapse. Physicochemical properties of the soil samples were measured in the laboratory. Results show that soil slope failure is controlled by three factors: (1) the typical geological structure of the mud forest area represented by an upper layer of thick loess sub-sandy soil and the near-vertical slope morphology; (2) particular soil properties, especially soil dispersibility; and (3) special climate conditions with distinct wet and dry seasons.