Climate-proof coastal protection with 'living dikes'

News - 21 March 2023 - Webredactie

Dikes protect the Netherlands from flooding. To keep the Netherlands safe in the future, several dikes are being reinforced in the High Water Protection Programme. The traditional way of strengthening dikes involves 'hard' (asphalt) revetment, but this is at the expense of the natural environment. Therefore, the 'Living Dikes' project looks at dike reinforcement using 'building-with-nature' methodologies. Various parties, including TU Delft, are investigating how 'living dikes' can play an important role in climate-proof coastal protection while preserving nature and landscape.

Leon Hermans, involved in the project from TU Delft's TPM faculty: 'Traditional dike reinforcement regularly requires raising and widening the dike. Such a 'hard' solution is easy to implement and is supported by technical guidance documents, calculation models and funding structures. The downside is that this leads to ever higher and wider dikes in many places, at the expense of the quality of the landscape and nature'. 'Living dikes' are green dikes with a salt marsh that grow apace with sea level rise. They can play an important role in climate-proof coastal protection. 'By using natural forelands, dikes themselves need to be less high and wide while still providing the same level of protection.'

Other collaboration needed

The research team at TPM, led by Hermans, is looking at governance aspects in the project. Realising and maintaining living dikes requires different collaborations than classic 'hard' dikes. 'Dike strengthening and maintenance is no longer exclusively a matter of water boards or Rijkswaterstaat, but also of nature organisations and private land managers, of municipalities, provinces, farmers and local residents. Multiple functions and values are also at stake, besides just flood protection: nature, landscape, recreation, agriculture and regional development,' says Hermans.

PhD researcher Esmee Bannenberg studies how parties in this complex playing field can agree on arrangements for "adaptive joint action": joint learning arrangements in which living dikes can be deployed in an adaptive manner. As a result, agreements on the layout around the dike in the long term are not set in stone, but parties have made process agreements on how to deal with the changes the future will bring. Bannenberg: 'This should make it possible to realise 'living dikes' now, despite existing uncertainties about future developments in climate, nature and environment.' The basic assumption is that cooperation will add value, but that the various parties involved in the dike stay within the boundaries of their own critical interests. This could involve, for example, legally stipulated flood standards that may not be exceeded, that management and maintenance costs remain divided reasonably between parties, or that sufficient natural dynamics remain possible, with sufficient diversity of species. Bannenberg explains that the adaptive approach allows for timely adjustments when necessary. 'This is of great importance so that water safety is not compromised in the future, despite the innovative and dynamic nature of living dikes.'

Complex challenges

The first phase of the research is now well under way. Besides Bannenberg and Hermans, TPM researchers Jill Slinger and Heleen Vreugdenhil are also involved, as well as Deltares researcher and TPM alumna Stephanie Janssen. It is clear from the initial results that the task of realising Living Dikes is even more challenging than initially thought. Not only do different parties have to agree on "adaptive joint action", but the conversation is no longer exclusively conducted within the flood safety arena. Linking with other policy arenas around nature, sustainability, climate and area development, is essential for a 'Living Dike' and adds another layer of complexity. 'We are currently mapping this network of linked arenas ('Network of Adjacent Action Situations') around Living Dikes for the Wadden Sea coast in the Northern Netherlands. In the next research phases we will develop a process tool to support parties in 'adaptive joint action' based on this', explains Hermans. 

About Living Dikes

In the Living Dikes project, TU Delft, University of Twente, NIOZ, Van Hall Larenstein, Deltares, University of Groningen and other partners are investigating "nature-based solutions" to achieve resilient and climate-proof coastal protection. The overall project leader is Bas Borsje of the University of Twente. Read more about the NWO Living Dikes project