Sediment Modeling of Hydraulic Flushing: General Guidelines

Reservoirs have been built on rivers to provide various benefits; undesirable consequences, however, have been resulted in. One of them is reservoir sedimentation – a large amount of inflowing sediment is blocked by the dam, causing deposition within the reservoir and sediment starvation downstream. Reservoir sedimentation reduces the reservoir storage capacity, increases the risk of plugging the water intake, and impacts the eco-system negatively.

Hydraulic flushing is an often-adopted method to remove deposited sediments in reservoirs by opening bottom outlets. In practice, reservoir managers need to determine the type, the optimum flushing schedule and water release rate. Numerical models are often used to make an informed decision. At represent, general guidelines are lacking on the proper use of numerical models for hydraulic flushing modeling – a gap this paper attempts to address. In this paper, various 1D, 2D and 3D numerical models are introduced and reviewed. General guidelines are presented on how to select a proper numerical model given a specific type of reservoir and flushing method, along with a discussion of the reliability of the model results. Three types of hydraulic flushing methods are relevant and discussed: drawdown flushing, pressure flushing and turbidity current routing.