Smart sand trap design as part of environmental friendly sediment management in small rivers
Treść / Zawartość
Both to reduce sediment inputs into the main river or the North Sea and to improve the water and bed quality of the small rivers, an effect-oriented as well as a source-oriented approach is followed to tackle the integrated water sanitation management of Flemish rivers. In the effect-oriented approach, an optimum design of a sand trap is engineered. As pollutants are mainly fixed to the fine suspended material, it is valuable to separate the relatively clean sand particles from the heavily polluted fine fraction. Hence, the amount of polluted material to be dredged and consequently the treatment costs are reduced. The smart sand trap idea is specifically applied to the Mark-Vliet catchment, a trans- boundary Dutch-Flemish river catchment. The Mark-Vliet river system transports bed material and heavily polluted suspended sediments to the Volkerak-Zoom lake. To protect the living, working and recreation areas in this catchment, a proper integrated water management is essential. A systematic control and sanitation of the polluted sediments in the river environment will help to stop the further degradation of the water quality. Starting from an existing sand trap configuration, an adapted construction is designed through physical scale model tests taking into account the practical and economical issues of the project. As exact simulation of sediment transport in a physical scale model is almost impossible, the basic philosophy of the model tests was to examine the flow patterns as the driving forces for the related sediment transport image. The operation of the optimum sand trap configuration relies on three basic principles: an upstream bifurcation ensures a proper deflection of suspension transport in a parallel deviation; a downstream sill controls the flow distribution over the respective main and deviation branch for different regimes; an underwater sill at the entrance of the lateral deviation forces the transport of all sand material near the bottom into the sand trap.
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