Anthropogenic disruption of sediment connectivity by embankment dams in the fast-eroding badland basin

Abstract

Human-induced disruption of sediment connectivity is a major driver in shaping the Earth's surface. Check dams and reservoirs are common for water storage and sediment retention in rapidly eroding landscapes, which interrupt sediment transport. However, isolating the effects of anthropogenic structures on landscape evolution remains challenging. Here, we assess the effects of embankment dams in the mudstone badlands of southwestern Taiwan. Using 50 years of fluvial sediment load data, rainfall records, and airborne LiDAR DEM, we suggest that dam construction has altered sediment dynamics from source to sink. Our results indicate a 79 % decline in downstream suspended sediment loads between 1970 and 2023, despite increasing annual rainfall and the expansion of badland areas. In addition, we found that the erosion of mudstone badlands leads to the formation of flat-bottomed valleys (FBVs), which are transformed into agricultural lands and fish ponds. Yet, the difference of DEM (DoD) between 1986 and 2016 indicates that FBVs with dams have accumulated sediment volumes three times higher than FBVs without dams, and at such deposition rates, 87 % of the FBVs have silted up within 50 years. In short, our findings demonstrate that the embankment dams alter sediment loads and reshape fluvial–coast connectivity. Integrating anthropogenic structures into long-term catchment management is essential for restoring sediment connectivity and mitigating sediment-related risks.