Bank erosion in regulated navigable rivers: Towards a process-based model of bank retreat

After the European Water Framework Directive, riverbanks in several countries had the protections removed to improve the water quality and the river ecosystem. Particularly, the Meuse River currently has several kilometres of freely eroding banks, which may have consequences for other river functions such as navigation and flood conveyance. The understanding, quantification and prediction of the morphological evolution of restored banks is thus relevant to manage the integrity of all river functions and improve future restoration practices. This work analyses the results of a recently developed model to estimate bank retreat in regulated waterways and compares them with measured profiles. The model essentially accounts for the major drivers of erosion, i.e., primary and secondary ship waves, considers homogenous cohesive banks, and computes erosion rates through a Partheniades-type of formulation. The results show a good qualitative and quantitative agreement with measurements. Erosion rates are yet not accurate with the current approach, for which future work will focus on improving the temporal representation through the inclusion of other factors and processes affecting erosion rates. These are, for instance, statistically representative time series of ship waves, currents during floods, and elements affecting erosion processes such as mass failures, slump-block dynamics and vegetation.