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UBC Theses and Dissertations

A visual model for predicting stream response of alluvial gravel-bed rivers Moscote, Nerissa Yarmilla

Abstract

In this thesis, a visual optimization model, RiverMod, has been developed to predict the channel geometry of alluvial gravel-bed rivers. The model is an extension of a previous model developed by Millar and Quick (1993b). The model is based on equilibrium theory, and also includes a bank stability analysis. The adjustment of the dependent variables of a river reach is quantified according to changes incurred by the independent variables. The primary dependent variables are channel width, depth and slope, and the primary independent variables are the discharge, flow resistance parameters, sediment size distribution and bank stability parameters. RiverMod, written in Visual Basic, provides a user interface that promotes clear and simple model usage for multiple runs with different sediment transport and flow resistance equations. The theory behind the Millar and Quick (1993b) model is discussed, as well as Millar's (2000) meandering-braiding transition and its incorporation into RiverMod. Four sediment transport equations and four flow resistance equations are included as part of the model. The model consists of fixed-channel-slope and variable-channel slope versions. The fixed slope version is equivalent to an experiment where the slope is fixed, and the channel width, depth and sediment transport rate adjust to the discharge. The variable slope version more closely approximates natural stream conditions. Each of these models can be applied to streams with cohesive or non-cohesive bank sediment. The model is applied to two gravel-bed rivers, located in British Columbia. The bank stability of both rivers has been decreased due to logging along the banks. RiverMod is used to quantify the impact of such a disturbance by analyzing past and present channel conditions. Restoration methods are suggested based on model output. This thesis provides a full description of theory underlying the model development and a description of model usage; therefore, this thesis is a complete user manual for the RiverMod optimization model.

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