3D Numerical Study of Time Dependent Bed Changes in the Flushing Channels for Free Flow Sediment Flushing in Reservoirs

Abstract

Dams are extensively used for different purposes (i.e. irrigation, water supply, flood control and hydro-electric power supply) and flushing is one of the proposed methods for preserving the storage capacity of dam reservoirs. In the free-flow sediment flushing, the water level is drawndown during a flood and subsequently the increase in the flow velocity results in sediment erosion in dam reservoir. The efficiency of the free-flow sediment flushing depends on various parameters such as hydraulic condition, sediment properties and reservoir geometry. Owing to this fact that advanced numerical models could simulate many aspects of the hydraulic characteristic of flow and sediment erosion-deposition field, application of these models could provide the initial assessment of the different impacts of upcoming free-flow sediment flushing. In the present study a fully 3D numerical model, SSIIM, used for assessing the temporal bed changes during the free-flow sediment flushing in various shallow reservoir geometries. The outcomes of the numerical simulations reveal the capability of the 3D numerical model to simulate the different stages of channel formation in shallow reservoirs and also modeling the flow field when the bed topography is in the equilibrium condition.