A Framework for Evaluating the Long-Term Efficiency of Coastal Nature-Based Solutions: Assessing Surface and Subsurface Processes

Nature-based Solutions (NbS) are widely known as effective strategies for enhancing coastal resilience to climate change. However, assessing their long-term efficiency remains challenging due to the complex interacting processes within coastal systems and the uncertainties associated with future climate scenarios.

Many existing frameworks for evaluating coastal NbS focus on single-domain systems, often simplifying key processes to reduce the complexity of modeling. However, coastal systems are inherently complex and include not only surface processes but also the subsurface groundwater domain. Therefore, to successfully integrate NbS into landscape planning and study their long-term efficiency, it is essential to understand the entire system, and to quantify the relevant interactions between surface and groundwater processes and their influence over the system’s resilience.  

This research introduces a framework to evaluate the long-term efficiency of coastal NbS by identifying key surface and subsurface (groundwater) processes and trade-offs and synergies within the system. The framework is designed for application in coastal systems characterized by sandy beaches and sedimentary aquifers and its applicability is demonstrated through a case study on the island of Terschelling. For the case study, two NbS are evaluated: (1) a beach nourishment from 1993 and (2) the potential implementation of Managed Artificial Recharge (MAR). The long-term efficiency and resilience to climate change of these solutions are quantified using ecosystem, geomorphological, and hydrological indicators through numerical modelling (using Delft3D and Modflow) and scenario-based analysis.

Additionally, the study highlights the importance of understanding how NbS may require time to enhance the system’s resilience or lead to unexpected impacts under future climate conditions. Providing a better overview of trade-offs and synergies can reduce the uncertainty related to the long-term component, facilitating the uptake of NbS as a sustainable coastal management solution.