How can you optimise seagrass meadows as a nature-based solution for coastal hazards? 

The EDITO Platform offers some of the best ocean numerical modelling tools to support decision-making on coastal zone management, leveraging the power of Nature-based Solutions (NbS). One such tool includes the EDITO-Model Lab’s What-if Scenarios (WiS). This model system, configured by Hereon using the SCHISM modelling framework, simulates complex interactions between hydro-, wave-, and sediment dynamics, with a vegetation module that accounts for the drag effects of seagrass on these dynamics. 

By comparing seagrass NbS scenarios with a reference scenario, various types of users – from skilled numerical modellers to researchers and technicians, from high-level decision-makers and local policy implementers to the wider public - can assess the hydrodynamic impacts of seagrass meadows on coastal hazards. The results reveal key insights into reduced coastal erosion risks and other benefits, helping coastal protection agencies, policymakers, and scientists make data-driven decisions. 

Pre-calculated experiments and custom scenarios 

The North Sea German Bight region served as a test site for this EDITO WiS. Pre-calculated seagrass experiments are available via a container application, enabling users to explore different seagrass configurations and evaluate their impacts. Users can run multiple iterations, comparing outputs — displayed as graphs and visualisations — to identify the most optimal seagrass setup. 

Additionally, an on-demand application is under development for advanced users, allowing them to create tailored setups for specific locations. These customised simulations running on high-performance computing (HPC) infrastructure will be accessible through a Jupyter Notebook on the EDITO platform. Users will need to apply for computational time on EuroHPC systems and configure SSH keys before running the simulations. Once completed, the results seamlessly integrate with the platform’s plug-and-play functionality.

A simplified scheme of how EDITO-Model Lab is developing WiS to optimise seagrass NbS to help fight coastal hazards. 

Seagrass meadows as a powerful NbS for coastal defence

Seagrass meadows are a key NbS for coastal protection in some specific coastal environments, such as coastal lagoons and estuarine areas. By acting as natural barriers, seagrass reduces wave energy and stabilises shorelines. This is especially critical in the context of rising sea levels and increasing erosion risks due to climate change. Seagrass meadows help mitigate coastal hazards in two major ways: 

• Wave Energy Reduction: Seagrass meadows interfere with wave processes, reducing wave energy along the coast. This reduces the risk of coastal flooding — a growing concern with sea-level rise.
• Coastal Erosion Prevention: The presence of seagrass root systems in the seabed helps stabilise sediment, decreasing the risk of coastal erosion. The combination of reduced wave energy and stronger sediment retention creates a more resilient coastal ecosystem. 

Unlike traditional engineered coastal defences, NbS offer sustainable, cost-effective solutions that also enhance biodiversity, promote carbon sequestration, and improve water quality

How EDITO-Model Lab WiS supports informed decision-making 

The EDITO-Model Lab WiS enables decision-makers to explore NbS configurations and visualise their impacts in a clear and accessible format. Coastal protection agencies and policymakers can assess different configurations—such as seagrass density, height, and placement—to identify the most effective solutions for mitigating risks in specific areas. This approach not only optimises coastal protection but also reduces costs by allowing users to simulate potential outcomes before implementation. 

For example, coastal zone managers can use the WiS tool to determine where seagrass meadows will be most effective in reducing erosion or protecting communities from flooding. By offering a clear visual output of results, WiS aids transparent, data-backed decision-making processes, improving the efficiency and success of NbS strategies. 

WiS model workflow: a coupled modelling system is utilised for scenario simulations contrasting a user-defined seagrass scenario (prescribing via the vertical seagrass extension range) versus the no seagrass references. The simulation outputs are evaluated based on key metrics. 

Efficiency metrics to quantify NbS success 

The efficiency of each NbS simulation within the EDITO-Model Lab WiS is quantified through several key metrics: 

• Wave Height and Water Elevation Reduction: Changes in wave height and water elevation are tracked to measure the impact of the seagrass meadow on coastal wave dynamics.
• Sediment Concentration and Bottom Stress: These variables indicate how well the NbS stabilises the seabed and reduces erosion risks.
• Erosion Risk Score: A colour-coded erosion risk score is calculated, based on the relative exceedance of critical shear stress during the simulation, indicating how well the solution reduces erosion over time. 

For the pre-calculated experiments, results are delivered within minutes on the EDITO cloud. High-resolution setups, such as the expert grid for the German Bight, achieve a speedup of approximately 40x faster than real-time on HPC infrastructure using 1,000 CPUs. 

Managing errors and uncertainties to enhance credibility 

Clear communication of errors and uncertainties is essential to ensure the credibility and future use of the EDITO-Model Lab’s WiS for NbS. A standardised validation protocol will be applied, reporting error statistics such as bias and root mean square error (RMSE). This will be based on comparisons of model outputs with observational data from sources like tide gauges and wave buoys. 

Although direct error quantification for hypothetical WiS scenarios is not possible (due to the lack of existing observational data for seagrass meadows), uncertainties will be transparently communicated. For instance, the current model represents seagrass as non-flexible cylinders and excludes biological growth dynamics, which may lead to an overestimation of erosion reduction benefits. However, these limitations do not impact the relative comparison of different scenarios, allowing users to confidently identify the best options among the simulations. 

Results of NbS assessment. a) Green colour shows the location of seagrass in the NbS scenario.  b) Difference in 95th quantile of wave heights, demonstrating seagrass effectively attenuates waves. c) Similar to b) but for sediment loads. It shows that less sediment is mobilised  as a consequence of reduced erosion. d) and e) represent the bottom shear stress-based risk metric quantifying the exceedance ratio of erosion critical shear stress for the case with and without NbS, respectively. f) displays the risk change due to seagrass given by the difference e) - f). 

User engagement during co-design and exploitation to boost uptake

The EDITO-Model Lab WiS is designed with user involvement at its core, ensuring that the tool meets the needs of a wide range of stakeholders, from modellers to policymakers. 

• Beta Users (Model Developers): The co-design process begins with beta users, who provide early feedback to refine the application. This user group helps shape the tool’s development, ensuring it meets practical needs. 
• Intermediate Users (Scientists): Intermediate users, such as regional and coastal modellers, contribute to both the design and exploitation of the application. Their use of WiS in research generates new insights that improve our understanding of NbS and coastal dynamics. 
• End Users (Coastal Protection Agencies, Policymakers): End users, including coastal zone managers and government agencies, are involved in the final exploitation stage. They use the results generated by WiS to inform decision-making and guide the implementation of NbS. By engaging end users throughout the development process, EDITO ensures that the tool is tailored to real-world applications, making it highly relevant for planning and managing coastal protection strategies.

Optimised coastal protection through technology and nature 

The EDITO-Model Lab WiS tool is a powerful solution for optimising nature-based coastal defences like seagrass meadows. By simulating different scenarios, users can explore the most effective strategies to protect coastlines from erosion and sea-level rise while promoting biodiversity. Whether you are a researcher, policymaker, or coastal manager, the EDITO-Model Lab WiS provides the tools you need to make informed, cost-effective, and sustainable decisions for coastal protection. 

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