Modelling bank retreat in a single river bend

Bank erosion processes represent an important factor in driving planform changes, meander development and channel width adjustments in alluvial rivers. Recent literature of the last decade has shown that bank retreat process often involves combination of fluvial erosion and mass wasting, giving important contribution to the amount of sediment delivered downstream. But, at authors knowledge, few attempts have been made to combine the bank stability modelling at the reach scale with the recent advances made on morphodynamic modelling of more complex natural patterns, such as meandering rivers. The present work develops a model of bank retreat at the scale of a single meander bend, as a first step to understand the coupling between bank erosion and the complex bed topography induced by the hydrodynamics occurring in a meander bend. In this preliminary phase the model will be constituted by three steps: the flow and bottom topography in a constant curvature channel, bank stability analysis for mass failure, fluvial erosion. The developed model can be applied at the scale of a single flow hydrograph to better understand the interaction between bank retreat and flow hydrodynamic. As a preliminary result, the model is here applied to the case study of the Cecina River, a gravel bed river with very steep migrating outer banks and a sinuous meandering planimetry. Some preliminary test cases of bank stability with an idealized geometry, recalling the Cecina’s banks, are here reported to confirm the goodness of the employed model.