Determination of Sediment Trap Efficiency in Detention Dams Using Physical Model

Detention dam is one of the major flood controling structures. For practically encountered sedimentation problems, some extra volume is usually considered in dam design which should be estimated correctly. One of the effective parameters in this regard is sediment trap efficiency. The aim of this research was to determine the sediment trap efficiency of detention dams while the flood outflow synchronizes with flood inflow. The experiments were conducted in a special channel designed in the “Watershed and Soil Conservation Research Center”, using two kinds of sediment materials and a channel with gradient of 2.5-6 percent, sediment materials concentration of 4-11.5 percent and the flood volume of 100-300 liters. Undimensioned factors were determined and calculated within the experiment limits using dimension analysis, and their effects on the sediment trap efficiency were studied. The effective undimensioned factors were taken into consideration with the use of multi-regression analysis. Also, some proper relationships were introducted on the basis of undimensioned factors analysis. and flood-reservoir characteristics using multi-variable nonlinear regression in order to determine the sediment trap efficiency.In order to evaluate each of the relationships obtained from multi-variable nonlinear regression, relative error and determination coefficienct in each case were determined and finally, the most suitable relationships were suggested.