An optimization model for the development and response of alluvial river channels

In this thesis an optimization model has been developed to calculate the equilibrium geometry of alluvial gravel-bed rivers for a given set of independent variables. The independent variables are the discharges, both the magnitude and duration which are represented by a flow-duration curve; the mean annual load, both volume and grain size distribution, which is imposed on to the channel reach from upstream; and the geotechnical properties of the bank sediment. The unknown dependent or decision variables to be solved for include the channel width, depth, bank angle, roughness, and grain size distribution of the bed surface. The dependent variables adjust subject to the constraints of discharge, bedload, bank stability, and valley slope, to determine a channel geometry which is optimal as defined by a maximization of, which is the coefficient of sediment transport efficiency. The work in this thesis is an extension of earlier models that have predicted the geometry of sand and gravel rivers with reasonable success, however the degree of scatter associated with these models limited their application to quantitative engineering applications. The advances in this thesis over the earlier optimization models are the inclusion of the bank stability analyses, modelling using the full flow-duration data, and calculating the grain size distribution of the bed-surface. The formulation presented in this thesis is specific to gravel-bed rivers, however it can be reformulated for sand-bed rivers.Applied Science, Faculty ofCivil Engineering, Department ofGraduat