Design of Sediment Traps with Open Check Dams. II: Woody Debris

Abstract

Sediment traps with open check dams are widely used structures in flood hazard mitigation. This paper and its companion review the literature on their design. The companion paper examines hydraulic and deposition processes associated with sediment transport. However, field feedback has shown that open check dam behaviors during floods are dramatically influenced by the presence or absence of driftwood. To better assess large woody debris hazards and influences, this paper first reports the methods available to estimate driftwood production in terms of volume and dimensions. Information is given on their recruitment and transfer in the catchment. The presence of driftwood and the relevance of trapping them strongly influence the choice of the suitable shape and type of the open check dam. The performance of the different open check dam shapes in terms of driftwood management is detailed. Design criteria to estimate clogging probabilities, trapping efficiencies, volume capacities to trap driftwood, and hydraulic head losses due to driftwood accumulations are detailed. A step-by-step design procedure is proposed and finally suggestions to complete today’s knowledge are outlined.