Infrastructure Engineering - Theses

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A sediment-routing model for alluvial streams

Wellington, Neil Bruce ( 1978)

Using the complete one-dimensional equations of momentum and continuity of fluid-flow, the one-dimensional equation of sediment continuity and several appropriate transport relations, a computer simulation model is derived which is capable of routing flow and sediment through a channel reach with a moveable bed and irregular boundaries. Sediment is assumed to be transported in two modes; as suspended-load and as bed-load. The bed-load transport rate is assumed to react instantaneously to local alterations in flow conditions, while the suspended-load is assumed to take a finite time to react to local flow changes. For non-uniform bed-sediments, the total contribution to erosion or deposition at each computational point in the channel is obtained by summing the individual bed-elevation changes arising from changes in the bed-load and suspended-load for each size fraction. Flow conditions computed by the flood-routing component are then adjusted to allow for erosion or deposition before computations proceed to the next time increment. The concept of erosion probabilities, introduced by Einstein (1950) is used, along with implicit allowance for the occurrence of bed-forms on the stream bed. Several examples of model performance are presented, in which the effects of several significant parameters are demonstrated.