Turbidity-Induced Sedimentation in Closed-End Channels

Abstract

The mechanism by which turbidity currents propagate and cause sedimentation in closed-end channels such as pier slips and residential canals was studied in laboratory experiments. Two similar flumes were used, each consisting of a main channel carrying fine-grained sediment-laden flow and an orthogonally placed closed-end channel with a gated entrance. Characteristics of the turbidity current and sediment deposition in the closed-end channel were investigated following gate opening. Behavioral similarities as well as basic differences between turbidity current and non-settling gravity currents were observed. Several properties, e.g. suspension concentration, showed exponential-type decay with distance. The ratio of sediment settling velocity to the densimetric velocity was found to be a significant parameter for comparing results from tests using different sediments. Sediment influx rate through the entrance was found to be proportional to 3/2 power of suspension concentration at the entrance. This relationship yields a simple method to calculate the amount of sedimentation in the channel.