Nature-Based Solutions for Bank Protection along Estuarine Waterways
The banks of estuarine waterways are exposed to high loads due to tidal water level changes and currents as well as changes in salinity. Similarly, large current and wave loads are experienced as a result of wind waves and large seagoing vessels.
Due to the diverse uses of the estuary, it is important in many places that the shoreline must be secured which contradicts estuary dynamics. Technical-biological bank protections offer a solution in which technical (armour stones, mesh baskets, building materials made of iron and wire, etc.) and biological (dead wood, living plant material, natural fibers such as bast and coir) materials are combined individually and in a variety of ways depending on the protection requirements. When using armourstones, only inert armourstones should be used for ecological reasons so that they can be colonized by organisms.
In 2019 the Federal Institute of Hydrology (BfG) and the Federal Waterways Engineering and Research Institute (BAW) started investigating the applicability and the ecological effectiveness of nature-based solutions for bank protections in estuaries to develop technical guidelines and recommendations for practitioners. In doing so, the Federal Institutes are collaborating with practitioners within the Federal Waterways and Shipping Administration (WSV) who already implement various traditional bank protection measures using e. g. dead wood. In the heterogeneous conditions of brackish tidal estuaries, bank protection with living materials however remains challenging and is therefore applied less frequently. The same applies for indirect measures such as reprofiling and flattening of steep bank slopes.
A compilation of implemented bank protections using nature-based solutions in the tidal estuaries of the Elbe, Weser, Ems and Eider can be found here:
Compilation of nature-based solutions for bank protection in German estuarine Federal waterways