Nature-Based Bank Protection in Practice: Experiences from German Estuarine Waterways

The banks of tidally influenced federal waterways are are subject to competing land- and water-based uses. Consequently, banks are often reinforced with riprap revetments to protect them and adjacent tidal marshes from ship-induced erosion, which results in the loss and fragmentation of marsh habitats. Nature-based solutions for bank protection (NbS-BP) have the potential to combine the technical stabilization requirements with ecological functions. This article presents application-oriented recommendations for the most commonly implemented measure types, derived from case study evaluations and established theoretical understanding.

Results demonstrate that NbS-BP – ranging from living and dead wood measures to the structural improvement of riprap revetments – are already being implemented along estuarine waterways in Germany. However, under substantial ship-induced bank stresses, measures involving dead wood or vegetation require specialized expertise, practical experience, and conceptual innovation to ensure reliable performance. In such contexts, technical interventions may be necessary to modify prevailing boundary conditions in a space-efficient manner, enabling ecological stabilization functions and ensuring sustainable erosion protection. At highly exposed sites, a complete replacement of conventional revetments is often not feasible due to high maintenance requirements or unacceptable risks. In these cases, existing riprap structures can be enhanced with structural modifications that create small ecological stepping stones by providing microhabitats for site-native plants and animals. While these are low-maintenance options, the ecological value generally remains lower than that of living or dead wood NbS-BP measures. Overall, the results highlight that NbS-BP can be applied across a wide range of estuarine settings, yet their development and performance remain inherently site-specific and associated with higher uncertainty than conventional armouring. Therefore, measure types must be selected and adapted to prevailing local conditions to minimize uncertainties related to material durability and long-term functionality, particularly amid resource constraints under current shortages of specialized expertise.