Author(s): Lukas Vonwiller; David F. Vetsch; Robert M. Boes
Linked Author(s): Robert Boes, David Vetsch
Keywords: Bank erosion; Sediment transport; Morphological modelling; Numerical modelling; Grid dependency
Abstract: Numerical models for the simulation of morphological changes in natural rivers have to account for bank erosion. This dynamic erosion process depends on the critical shear stress of the bank material, the flow and gravity-induced latera transport, and the bank failure mechanism. To take bank erosion in a numerical model into account, different mode concepts have to be considered and combined. We use a numerical depth-averaged 2-d model to simulate bank erosion in a straight trapezoidal channel with non-cohesive material based on Ikeda’s laboratory experiments. The bed load transport model includes Ikeda’s lateral transport approach and a geometrical approach for bank failure including the definition of the angle of repose for dry and submerged material. We study the role of these modelling approaches and the sensitivity of important model parameters. Interestingly, not only is lateral transport important, but also bank failure plays a crucial role. The most sensitive parameters for bank failure and the overall progressive erosion process are the angle of repose, the pre-factor of the sediment transport formula, the pre-factor of the lateral transport approach, and the grid resolution. By calibration of these parameters the results of the numerical model agree well with the experimenta data. In particular, the dynamics of the lateral erosion and the aggradation of the channel bed are well captured However, the model results strongly depend on the discretization of the computational grid. To overcome this shortcoming, alternative approaches are discussed in this contribution.
Year: 2015