Predicting Debris Flow Check Dams Siltation Times Considering Climate Change: A Case Study of the Bailong River Basin (Gansu Section)

Debris flows are a common natural trigger of mountain disasters, and gravity-type check dams are one of the most representative soil and water conservation measures in the Bailong River basin. Despite the prevalence of gravity-type check dams, scholarly research on calculating deposition thickness for each debris flow event intercepted under future precipitation scenarios is lacking, hindering accurate predictions of dredging or expansion timing. This study developed a prediction formula for deposition thickness behind the check dam. The formula is applicable to debris flow events that the dams can intercept. By analyzing the mathematical relationships among slope ratio before and after deposition, channel width, distance to the check dam, and peak discharge, the thicknesses of debris flow depositions at certain positions can be calculated, offering a new approach for predicting check dam siltation times. The newly proposed prediction formula was used to calculate the deposition thicknesses behind the dam for five debris flow events, and was applied to channels with similar Melton Indices where check dams are constructed. The deposition processes of the five debris flow events were simulated using Massflow software. Additionally, machine learning methods were employed to predict precipitation scenarios and debris flow I-D threshold curves, thereby determining the rainfall likely to trigger debris flows in catchments. Results showed that, with a duration of 900 seconds, the peak flood discharges of the five debris flow events were 40.83%–43.23%, 18.56%–22.99%, 17.89%–18.69%, 9.00%–12.10%, and 15.85%–21.06% of a 100-year return period, respectively. The study also demonstrated that the new method can be widely applied to calculate deposition thicknesses behind dams accommodating different debris flow events, aiding in optimizing check dam management and maintenance strategies and enhancing their efficiency and sustainability in water and soil conservation.