Health assessment of check dams in China's Loess Plateau at the watershed scale

Current health status of check dams and their flood control capacity amid frequent heavy rainfall remain unclear, partially due to lack of a comprehensive and efficient method for health assessment targeting potential heavy rainfall pressures. Thus, this study developed a health assessment framework for check dams under heavy rainfall scenarios, focusing on structural composition and integrity, siltation capacity, and flood control pressure. Indicators for these three aspects were calculated based on a real-scene 3D model and a high-precision DEM generated by unmanned aerial vehicle (UAV) tilt photography for a typical watershed on the Loess Plateau. Comprehensive health assessment of 138 check dams revealed that 14% were in excellent health, 16% in good health, 26% in fair health, and 44% in poor health. For those 44% check dams (61 in numbers) in poor health, corresponding actions were recommended based on the assessment results to reduce pressure from flooding, with 15 demanding prompt repairs, 12 requiring increased dam height, 16 needing spillway expansions, and the remaining 18 requiring multifaceted measures or the construction of new dams. At the sub-watersheds scale, more than 70% of the check dams in the Majiagou and Tianjiagou were destroyed or in poor health, which require special attention during flood seasons. In the framework developed in this study, indicators were easily accessible and highly accurate, making it suitable for practical application. This study provided a scientific basis and methodological support for decision-making regarding the reinforcement of existing and future planning of check dams in the Loess Plateau region.