Bank Erosion Processes in Regulated Navigable Rivers

Vessel-induced waves affect the morphology and ecology of banks and shorelines around the world. In rivers used as waterways, ship passages contribute to the erosion of unprotected banks, but their short- and long-term impacts remain unclear. This work investigates the effects of navigation on bank erosion along a reach of the regulated Meuse River with recently renaturalized banks. We apply UAV-SfM photogrammetry, RTK-GPS, acoustic Doppler velocimetry, aerial and terrestrial photography, soil tests, and multibeam echosounding to analyze the progression of bank retreat after riprap removal. After having analyzed the effects of ship-generated waves and currents, floods, and vegetation dynamics, a process-based model is proposed to estimate the long-term bank retreat. The results show that a terrace evolves in length and depth across the bank according to local lithology, which we clustered in three types. Floods contribute to upper-bank erosion-inducing mass failures, while near-bank flow appears increasingly ineffective to remove the failed material due to terrace elongation. Vegetation growth at the upper-bank toe reduces bank failure and delays erosion, but its permanence is limited by terrace stability and efficiency to dissipate waves. The results also indicate that long-term bank retreat is controlled by deep primary waves acting like bores over the terrace. Understanding the underlying drivers of bank evolution can support process-based management to optimize the benefits of structural and functional diversity in navigable rivers.