Influence of check dams on flood hydrology across varying stages of their lifespan in a highly erodible Catchment, Loess Plateau of China

Abstract

Check dams are applied worldwide as an effective approach for soil conservation. Its effect on hydrology, however, has not been fully understood. As a critical step towards revealing the lumped effect of check dams at the regional scale, this study explored the modified flood hydrology induced by check dams in a representative highly erodible catchment in the Loess Plateau, China. A coupled hydrological and hydraulic modeling approach was applied to simulate the flooding process in different stages of deposition and topographic changes in a check dam reservoir. The results suggest a paradigm shift of the dam effect on flood attributes, which transits from a total interception in the early stage of the dam to peak reduction and flood detention, rather than a complete loss of flood control functions, when it approaches the maximum capacity of sedimentation. Under the same level of deposition, the reduction of a minor flood by a check dam was higher than that of a major flood. The topographic changes contributed to the reduction of flood peak appreciably by reducing the flow velocity and retarding the flood propagation. Noticeably, this reduction was augmented with the advancement of siltation and topographic changes, indicating the persistence of the hydrologic effects of check dams in the long run. As a result of these hydrological changes, the reduction in the flood flow velocity induced by check dams suggests substantial reductions in sediment transport and channel erosion during floods. In addition, a dam system containing multiple, cascading check dams exhibits much more significant effect in modifying both hydrologic and hydraulic properties of flood than individual dams. The current research provides a mechanistic understanding of the effects of check dams on catchment hydrology under heavy rainstorm conditions in small catchments.