Abstract
Abstract. Sediment traps with partially open check dams are crucial elements for flood protection in alpine regions. The trapping of sediment is necessary when intense sediment transport occurs during floods that may endanger urban areas at downstream river reaches. In turn, the unwanted permanent trapping of sediment during small, non-hazardous floods can result in the ecological and morphological degradation of downstream reaches. This study experimentally analyses a novel concept for permeable sediment traps. For ensuring the sediment transfer up to small floods, a guiding channel implemented in the deposition area of a sediment trap was systematically studied. The bankfull discharge of the guiding channel corresponds to a dominant morphological discharge. At the downstream end of the guiding channel, a permeable barrier (check dam) triggers sediment retention and deposition. The permeable barrier consists of a bar screen for mechanical deposition control, superposed to a flow constriction for the hydraulic control. The barrier obstructs hazardous sediment transport for discharges that are higher than the bankfull discharge of the guiding channel without the risk of unwanted sediment flushing (massive self-cleaning).
Highlights
The sediment supply of mountain rivers is a substantial source for the dynamics of river ecosystems
Sediment transport-related criteria can be designated as “eco-morphological” river characteristics (Moyle and Mount, 2007). These characteristics can often be attributed to a certain discharge which alters and rearranges the channel bed morphology, which may be assessed by morphologically effective discharge (Wolman and Leopold, 1957a, b; Wolman and Miller, 1960)
The corresponding longitudinal evolution of the deposit is reflected in the top view picture of the deposition area (Fig. 8a) at the flood peak
Summary
The sediment supply of mountain rivers is a substantial source for the dynamics of river ecosystems Artificial barriers, such as dams, can affect the natural flow regime variability with direct impacts on the eco-morphological state of rivers (Allan and Castillo, 2007; Sponseller et al, 2013). Sediment transport-related criteria can be designated as “eco-morphological” river characteristics (Moyle and Mount, 2007). These characteristics can often be attributed to a certain discharge which alters and rearranges the channel bed morphology, which may be assessed by morphologically effective (dominant) discharge (Wolman and Leopold, 1957a, b; Wolman and Miller, 1960)
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