A Phenomenological Model for the Planimetric Evolution of Meandering Rivers and Related Database

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Bascom, Kerri
Meandering Rivers , Planimetric Evolution , Meandering River Database
This work concerns the planimetric evolution of free meandering rivers, whose associated riverbank erosion and channel changes notoriously pose a hazard to infrastructure within their vicinity as well as affect the health of the river ecosystem. It aims to address two research needs, those being (1) the lack of easy access to an ample number of experimental (i.e. laboratory and/or field) cases for which the hydraulic and geomorphic characteristics of the streams are detailed together with an account of their channel displacements over time, and (2) the shortage of zero-th order approximation models available to simulate and predict channel planimetric evolution. Based on the results of a rigorous literature review and survey of historical imagery archives, the former is addressed through the compilation of a database which couples the planimetric evolution of a river meander loop with its stream characteristics. The specific methodology used to extract the planimetric geometry from imagery is detailed, and if not specified in literature, the stream hydraulic characteristics are estimated using well established methods. The resulting graphical database includes information on 29 sites from 25 different sand and gravel rivers. The need for zero-th order models is addressed by focusing on eliminating the present limitations of the phenomenological planimetric evolution model by da Silva and Yalin (2017). A MATLAB computer program is introduced, which for the first time enables the automated application of the just mentioned model. A yet unknown multiplier-function embedded in the model is revealed on the basis of the computer program and field cases from the present database. The multiplier function was found to be a function of the width-to-depth ratio, in addition to stream sinuosity. The present applications of the model show that it can predict the spatial growth of meander bends of relatively symmetrical channels over several years not exceeding the development of a channel cut-off.
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