Integration of a geotechnical model within a morphodynamic model to investigate river meandering processes

Despite significant progress made in the research conducted to understand the morphodynamics of meandering rivers using computer models, a number of challenges and limitations remain with respect to simulating lateral river channel adjustments. In particular, some biophysical processes critical to bank erosion (e.g. related to soil and vegetation) are often neglected or oversimplified, proxy variables such as flow velocity are used to predict lateral migration rates, non-physical assumptions are frequently made to simulate channel cut offs, and channel and floodplain processes are commonly studied separately. The objective of this paper is not to address all of these issues, but to present a new geotechnical model that was integrated into a numerical morphodynamic model to include lateral erosion due to mass wasting. The model accounts for floodplain morphology and river bank hydrology, without compromising computational efficiency. The integrated geotechnical component includes a set of physics-based rules to quantify slope stability across the simulation domain. It is managed by a fully configurable universal genetic algorithm with tournament selection to efficiently calculate the spatial extent of block slumps whose slip surface profile is allowed to be planar, circular or irregular. This module is compatible with any type of mesh structure, making it suitable for the investigation of the dynamics of single- and multi-threaded river channels. Following bank failure, the fine material is assumed to be immediately entrained by the flow, whereas the coarse fraction is deposited along the formally unstable slope at the friction angle of the bank material. By keeping track of floodplain topography, and not solely of channel morphology, the model allows for preferential pathways to develop on the valley floor, which may affect both the direction and rate of channel migration.