Semi-two-dimensional numerical model for river morphological change prediction: theory and concepts |
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Authors: | Tew-Fik Mahdi |
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Institution: | (1) Département des génies civil, géologique et des mines (CGM), école Polytechnique de Montréal, C.P. 6079, Succ. Centre-ville, Montréal, QC, H3C 3A7, Canada |
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Abstract: | This paper presents a new numerical model for river morphological predictions. This tool predicts vertical and lateral cross-section
variations for alluvial rivers, which is an important task in predicting the associated hazard zone after a flood event. The
Model for the HYdraulics of SEdiments in Rivers, version 1.0 (MHYSER 1.0) is a semi-two-dimensional model using the stream
tubes concept to achieve lateral variations of velocity, flow stresses, and sediment transport rates. Each stream tube has
the same conveyance as the other ones. In MHYSER 1.0, the uncoupled approach is used to solve the set of conservation equations.
After the backwater calculation, the river is divided into a finite number of stream tubes of equal conveyances. The sediment
routing and bed adjustments calculations are accomplished separately along each stream tube taking into account lateral mass
exchanges. The determination of depth and width adjustments is based on the minimum stream power theory. Moreover, MHYSER
1.0 offers two options to treat riverbank stability. The first one is based on the angle of repose. The bank slope should
not be allowed to increase beyond a certain critical value supplied to MHYSER 1.0. The second one is based on the modified
Bishop’s method to determine a safety factor evaluating the potential risk of a landslide along the river bank. |
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Keywords: | River natural hazards Sediment routing Semi-2-D numerical model Stream tubes Stream power minimization Riverbank stability |
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