Substantial reduction in sediment yield after check dams in the Daliang Mountain region, Southwest China: Insights from sediment fingerprinting in a debris flow-prone catchment

Abstract

Study regionThe Daliang Mountain region, characterized by its widespread debris flow-pone catchments, is the primary sediment source area for the upper reaches of the Yangtze River, and has experienced intensive human activity over the past half-century. Study focusHere, we combined lake deposits with sediment source areas to quantify the sediment source and corresponding sediment yield (SY) in response to recent human impacts in a typical debris flow-prone catchment located in the Daliang Mountain region, Southwest China. The fingerprinting techniques, incorporating geochemical elements and their specific ratios, were used to characterize the sediment provenances and corresponding SY. New hydrological insight for the regionThe results indicated that gully erosion was the major sediment provenance (90.10 %) in the catchment, followed by cultivated land (6.76 %) and forested land (3.14 %) for the studied period. The temporal variations of SY showed two distinctive erosional stages in response to different human activities over the past 70 years, namely 1950−2004 and 2004−2020. Greater SY values, dominated by gully erosion, occurred from 1950 to 2004, implying that both critical national activities and revegetation projects have limited effects on surface sediment generation. In contrast, gully activity and resulting SY have sharply decreased since 2004 following the implementation of check dams. These comparisons indicate a central role of the check dam in reducing gully activity. The findings have important implications for policymakers to optimize the spatial layout of future soil conservation strategies in the region.