Improving the evaluation of slit-check dam trapping efficiency by using a 1D unsteady flow numerical model

Sediment trapping behavior of slit-check dams and related design criteria are usually evaluated assuming the hypothesis of steadystate hydraulic conditions associated with the peak of the design flood. A novel approach based on the use of a 1D unsteady flow numerical model to simulate in detail transport processes upstream from slit-check dams during flood events is presented in this paper. The adopted model is validated by comparison with results of laboratory experiments from the literature showing the ability to reproduce accurately the temporal evolution of the sediment deposit behind the dam. The presented model-based approach enabled a realistic evaluation of the sediment trapping efficiency of the dam during the flood, i.e., the percent trapped portion of sediment volume transported by the flood, for different sizes of the dam slit. Especially for narrow slits, simulations revealed lower trapping efficiencies of slit-check dams at the flow peak condition compared to an approach from literature based on the steady-state flow assumption. Also, simulations allowed for the evaluation of the behavior of the dam at the end of the flood event, revealing the potential of the model-based approach to analyze the morphological evolution of the river downstream of the dam.