However, there are structures in nature that both provide stability and move with changing conditions. Salt marshes, mudflats and shellfish reefs form living, self-sustaining buffer zones that curb erosion without being too rigid [1]. This combination of flexibility and robustness creates opportunities for innovative solutions in water management. Instead of building predefined structures, we are exploring whether adaptive, nature-inspired structures can develop into effective shoreline protection in practice. We are testing this approach in the Eastern Scheldt, a former estuary where large-scale shoreline erosion has occurred since the construction of the storm surge barrier and compartmentalisation dams.
Previous projects in this area used artificial oyster reefs as part of the ‘building with nature’ approach. As part of the Werken met Waterlandschappen (Working with Waterscapes) project, we are now taking the next step by looking at how spatial design can enhance these structures, not only as a wave attenuator, but also with a focus on re-establishing aquatic plants and other ecological functions.
Figure 1. Schematic representation of wave attenuation by different spatial arrangements of biogenic structures. Blue arrows indicate attenuated wave energy, red arrows show wave energy that can move unimpeded through the landscape.
From naturally occurring process to design principle
Artificial shellfish reefs have been used in the Eastern Scheldt and elsewhere as a ‘building with nature’ approach. These dam-like structures attenuate waves, limit erosion and act as substrate for shellfish. Although effective, they lack the flexibility and self-sustainability of natural reefs.
Natural reefs often consist of irregular clusters with open spaces and height differences. This organic ‘patchy’ structure creates a dynamic, adaptive landscape that moves with the sea level and sediment transport. This structure not only promotes sediment capture and biodiversity, but also forms a robust breakwater.
These properties have inspired a new design principle: no definitive blueprint, but a modular system that can adapt to its surroundings. A preliminary study [2] has shown that clustered layouts are effective in breaking waves and are ecologically richer than rigid dams (Figure 1). Positioning them away from the marsh edge leaves room for natural development. A linear dike mainly attenuates waves in the transverse direction, but has little effect on waves moving along the shoreline. An organic layout, on the other hand, is more effective at breaking waves from different directions. To determine the optimal configuration, we used an evolutionary algorithm that tested variants on aspects including wave attenuation, erosion reduction and sedimentation (Figure 2). Both model simulations and physical trials can help with selection. This approach leads to a modular design that can be adapted to local conditions and in response to landscape dynamics in the same way as natural systems.
From principle to practice: the pilot project at Rattekaai
To test the developed design principle in practice, a pilot project has been set up on the mudflats in front of the Rattekaai salt marsh, in the Eastern Scheldt estuary. The marsh edges in this area are under threat from sand starvation. Sand starvation is caused by an imbalance between constructive and deconstructive processes on the foreshore [3].
Reduced tidal flow reduces sediment supply, while waves slowly erode sediment and move it to deeper areas. As a result, mudflats are disappearing and marsh edges are eroding [3]. At locations without rock armour, the salt marsh is shrinking by around half a metre per year on average, while natural rejuvenation is lacking [2].
The design principle consists of two phases: an exploration phase in which possible configurations are broadly explored, and an optimisation phase in which the selected variant is optimised further in the field. Figure 2, above the diagram, shows three photographs: a natural oyster reef (left), a linear, dam-shaped oyster reef as a conventional design approach (centre) and an organic configuration of gabions (right) as an outcome of the design principle described here.
The pilot project at Rattekaai offers a unique opportunity to test nature-inspired shoreline protection in practice. Comparing traditional brushwood dams with the organic gabions offers a valuable learning process on the effectiveness of different approaches. The separate, strategically positioned elements together form a robust whole that can be adapted to the morphological dynamics of mudflats and salt marshes.
Within two replicate blocks, four trial plots have been set up, each measuring 25 by 25 metres, with a 25-metre gap. One plot without structures acts as a control zone. In a second plot, a traditional brushwood dam has been constructed 0.5 metres high across its full width.
In addition, two variants are being tested with gabions (0.5 x 0.5 x 0.5 m) filled with oyster shells. Both variants have the same coverage of 6% of the plot area, but differ in spatial distribution: randomly distributed or clustered in groups.
The hypothesis is that clustered structures are more effective at attenuating longer waves, which cause most erosion. The configurations have been optimised with an evolutionary search algorithm for maximum wave attenuation, both transverse to the coast and along the shoreline (Figure 1). The structures were installed in March 2024 and deliberately positioned at some distance from the salt marsh edge to allow proper monitoring of the effect and range on the surroundings.
During the pilot project, height developments between, behind and around the structures are systematically recorded using a laser scanner. Now, one year after construction, the first clear positive changes can already be seen. We are also monitoring wave conditions and sediment dynamics to test effectiveness under varying weather conditions. In the coming years, we will investigate whether and when the structures need to be repositioned closer to the salt marsh edge to support salt marsh rejuvenation, and which configurations are most robust as nature-inspired shoreline protection.
Figure 2. The evolutionary design principle for the spatial configuration of ‘biogenic’ structures
Discussion
In this article, we have shown how the nature-inspired design principle can guide the development of future-proof solutions to shoreline erosion. Although conditions in the Eastern Scheldt are specific, the underlying approach is broadly applicable. Where there is sufficient room for spatial integration, nature-inspired adaptive designs offer a promising alternative to traditional, rigid shoreline protection. Initial results from the pilot project at Rattekaai underline this potential.
Although it is still too early to reach definitive conclusions on morphological and ecological effects, the first signs are promising: sedimentation is visibly occurring both inside and behind the structures, and the wave attenuation effect is as expected.
Working with separate, clustered elements creates a flexible and scalable layout that is capable of moving with naturally occurring processes. This not only makes these designs more future-proof, but also increases the chances of natural biodiversity restoration. At the same time, this approach requires a different method to conventional solutions, as designing and optimising suitable configurations requires calculation and design efforts. Simple calculation rules and reduced complexity models (on which Figure 1 is based, for example) can speed up this process and help to select realistic and effective design alternatives at an early stage.
A key advantage of the developed design cycle is that it allows for multiple optimisations. Alongside wave and erosion control, a simultaneous focus can be placed on biodiversity, landscape quality and experience. This makes it possible to work with local stakeholders to develop robust and widely supported solutions. A logical next step is therefore to use the design cycle in combination with photorealistic visualisations for area development, in which variants can be explored and refined interactively [4]. This approach contributes not only to water safety and ecological added value, but also to the perception and appreciation of the landscape.
The pilot project at Rattekaai shows that working with natural principles not only offers a technical solution, but also requires a fresh mindset when it comes to shoreline protection. Instead of control and rigidity, the focus is on harnessing natural dynamics.
This requires flexibility in both design and management: allowing scope for adapting and monitoring, and acknowledging that further development is essential for success. It is precisely this adaptive approach that offers a resilient strategy for a changing landscape, and challenges us to approach shoreline protection not as an end point, but as an adaptive learning process.
This study was conducted as part of the ‘Werken met Waterlandschappen project’. Thanks to Paul Vertegaal and Mariëlle Schenk (Society for the Preservation of Nature in the Netherlands) and Jeroen Veraart (Wageningen University & Research) for their support, the Delta Technology Top Consortium for Knowledge and Innovation and the Society for the Preservation of Nature in the Netherlands for funding the study, and the province of Zeeland for funding the test set-up.
Shoreline erosion poses a threat to water safety and the natural environment all around the world. Harsh measures offer immediate protection, but disrupt naturally occurring processes. In the Eastern Scheldt, we are testing a nature-inspired strategy using gabions filled with oyster shells.
These biogenic structures curb erosion, stimulate sedimentation and promote biodiversity. The modular design is based on natural self-sustainability and can be adapted to changes in the environment. This creates a robust, adaptive form of shoreline protection that moves with naturally occurring processes. The approach is scalable and can be used in a wide range of waterscapes, provided there is scope for dynamics and adaptive management.
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