Five catchments with different debris-flow susceptibilities and various debris flow trace areas (DTAs) in Southwest China. Understanding sediment connectivity promotes identifying key regions of soil erosion. However, the impacts of disturbances in landforms and vegetation caused by debris flow on the sediment connectivity remained unclear. In this study, the spatiotemporal variations of sediment connectivity and its major drivers in five catchments were evaluated using the Sediment Connectivity Index (IC) and GeoDetector model. The results showed that the average IC values apparently decreased from 1987 to 2023 in debris flow affected catchments, while the average IC values in DTAs were consistently higher than those in Non-DTAs, with an average difference of 1.35. Additionally, IC values exhibited a significantly increasing trend (p < 0.01) from upstream catchments with low debris-flow susceptibilities to downstream catchments characterized as high activities of debris flow, ranging from −2.10–0.51. GeoDetector results indicated that anthropogenic factors were the primary driver of IC changes, while the explanatory power of DTAs, Elevation and Rainfall were also significant in debris-flow disturbed catchments. Factor interactions further enhanced the explanatory power of IC, predominantly as bivariate and nonlinear enhancement. This study highlighted debris-flow impacts on sediment connectivity and the synergistic control of multiple factors on catchment-scale sediment transport to guide soil and water conservation practices in debris-flow-prone regions. • Impacts of disturbances by debris flow on sediment connectivity (IC) were evaluated. • High IC values highly overlapped with debris flow trace areas. • Elevation, debris flow, and vegetation jointly controlled the spatiotemporal variations of IC. • IC values were positively correlated (p < 0.05) with the frequencies of debris flow. • Proper prevention and post-event management of debris flows help soil erosion control.
Wei et al. (Wed,) studied this question.