Tracking long-term cascade check dam siltation: implications for debris flow control and landslide stability.

Check dams represent one of the most important engineering solutions for debris flow prevention and control in mountainous terrains. However, the dynamics of siltation processes behind cascade check dams and siltation effects on check dam efficiency remain poorly understood. Here, we investigated the long-term silting processes and their effect on the development and propagation of debris flows at the cascade check dam in Hunshui Gully (HSG) in southwestern China. Multi-source topographic data from different time periods were combined with information on the frequency of debris flows over a 53-year period to determine silting processes behind check dams. Our results showed that (1) the siltation area behind check dams increased over 10 times from 1978 to 2019, reaching 26.28 ± 0.02 ha; (2) the slope of the channels first decreased and then increased, the slopes of the branch channels and the main channel exhibited a stepwise difference, and headward siltation at anaphase was present; (3) the cascade check dam group in HSG intercepted and stabilized a total of 40 ± 0.96 Mm³ of sediment in 45 years, which was 4 times more than the amount that was transported. We concluded that the cascade check dam group in HSG ensured effective debris flow control, and that the siltation behind check dams had significant functions in debris flow control and prevention. Moreover, the cascade check dam group possessed the functions of storage, energy dissipation, channel consolidation, and slope stabilization at different silting periods. [ABSTRACT FROM AUTHOR]