Monitoring Earthquake-Damaged Vegetation after the 2008 Wenchuan Earthquake in the Mountainous River Basins, Dujiangyan County

The 2008 Wenchuan earthquake destroyed large areas of vegetation in the Baisha River and Longxi River basins, in Dujiangyan County, China. There were several debris flow events in these mountainous river basins after 2008. Currently, these damaged vegetation areas are in various stages of recovery. This recovery vegetation improves the resistance of slopes to both surficial erosion and mass wasting. We introduce a probabilistic approach to determining the relationships between damaged vegetation and slope materials’ stability, and model the sediment and flow (hydrological) connectivity index to detect the hydrological changes in a given river basin, using the multi-temporal (1994–2014) remote-sensing images to monitor the vegetation recovery processes. Our results demonstrated that the earthquake-damaged vegetation areas have coupling relationships with topographic environment and slope material properties, and can be used to assess the slope material stability. Further, our analysis results showed that the areas with horizontal distance to river streams <500 m are areas that actively contribute sediment to the stream channel network, and are main material sources for debris flow processes in one given mountainous basin