Numerical modelling shows an old check‐dam still attenuates flooding and sediment transport

Abstract

Check dams are an effective and widespread measure for soil and water conservation around the world (e.g., in the Chinese Loess Plateau). However, the quantitative impact of a heavy silted check dam with small remaining storage capacity and large deposition area on river flow and sediment transport during floods remained unclear.In this study, to investigate this impact, a physics-based distributed hydrological model (the Integrated Hydrology Model, InHM) was employed to simulate runoff and sediment processes during floods in a small catchment with a check dam in the Loess Plateau, considering different heavy rainfalls and check-dam remaining storages. The model was calibrated and validated against the observed hydrographs and sedigraphs in two flood events and obtained satisfactory modelling performance (the Nash-Sutcliffe efficiencies > 0.70). The scenario modelling results showed that a heavy silted check dam still remarkably reduced and delayed the peaks of river flow and sediment rate, due to the attenuated surface flow movement and sediment transport on the deposition area. The largest flow peak occurred around the 85% silting stage of the check dam rather than the fully silting stage (100%). Even in the fully silted stage, sediment deposition continually occurred on the deposition area with a maximum deposition of 11,700 t sediment in a heavy-rainfall scenario and more sediment deposited on the tail-end regions of the deposition area than other regions after a flood. Moreover, in heavy silted stage backwater on the tail-end areas and gullies largely attenuated local erosion and promoted sediment deposition, indirectly reducing the total sediment yield of the catchment during flood. These results indicated that numerous ageing check dams built in the Loess Plateau and worldwide are still useful to attenuate flood risk and soil erosion, and sound maintenance and management of the check-dam will be beneficial to flood and soil erosion control.

Revegetation impacts on runoff generation processes in a typical loess catchment

“…The digital elevation model (DEM) of SJG with 25-m resolution was acquired from the State Bureau Surveying and Mapping to construct the 3-D finite-element mesh (Ran et al, 2021)…”

An advanced check‐dam sedimentation module: Laboratory validation and implementation in a distributed sediment yield model for field application

“…In Figure 8a Compared with the SEDCD models, the original reservoir module of Shi et al (2016) ignores both the backwater effects and the connections with the downstream channel of the check-dams. The backwater effect can promote sediment deposition in the check-dam and thus increase the STE (Ran et al, 2021), whereas the connection to the downstream channel would allow a portion of sediment to bypass the check-dam and thus reduce the STE (Bai et al, 2021). Figure 9b shows that for most of the check-dams, the single-event STEs simulated by the original reservoir module are always lower than those simulated by the SEDCD models; however, for a few check-dams, the original reservoir module predicts higher STEs (nearly 100%) than do the SEDCD models.…”

“…Figure 1a shows the spatial distribution of large check‐dams (with a storage capacity > 5 × 10 5 m 3 ) in the Loess Plateau region, and Figure 1b shows a typical large check‐dam in Huzhu County of Qinghai Province. The sediment trapped upstream of check‐dams forms a relatively flat area of deposition through aggradation, and the area extends upstream following each flood event (Ran et al, 2021; Xu et al, 2004). As a result, the longitudinal gradient of the original narrow and steep gullies was reduced, and the eroding gully stabilized (Lucas‐Borja et al, 2021).…”

“…White-box models are physically-based models that simulate physical processes in detail (Sajikumar & Thandaveswara, 1999), for example, hydrodynamic models for sediment transport in reservoirs and along river channels (Cao et al, 2004(Cao et al, , 2017He et al, 2012;Ran et al, 2021;Wu et al, 2005). Most hydrodynamic models are developed by coupling the unsteady flow routing equations (e.g., the shallow water equation) and the sediment transport equation (e.g., the Exner equation) (Das et al, 2020) based on mass and momentum conservation.…”

Recognition of suitable small watersheds for check dam construction on the Loess Plateau

“…Check dams are used for soil and water conservation worldwide (Ran et al, 2021). They are usually built across a channel or gully to retain runoff, induce sedimentation, and minimize soil and water loss (Abbasi et al, 2019).…”