Sandy Solutions for Rising Challenges

Abstract

Climate change is accelerating coastal erosion, posing growing risks to infrastructure, ecosystems, and livelihoods across the world’s coastal zones. While global and regional studies increasingly provide projections of physical shoreline change, they often fail to integrate these with the spatial distribution of exposed assets or the potential for adaptation measures. As a result, their utility for informing where and how interventions, such as beach nourishment, could serve as viable adaptation options remains limited. Current research typically treats coastal erosion, exposure, and adaptation in isolation, leaving a critical gap in support for strategic coastal planning, where cross-country and cross-boundary insights could enable more coordinated and effective responses.

Here we present a continental-scale framework that integrates shoreline-change modelling, infrastructure exposure, and nourishment suitability to inform coastal adaptation across Europe. We first compile a novel database of 1060 historical nourishment interventions spanning 70 years, capturing the spatial distribution, implementation motives, and coastal contexts, including borrow area, nourishment type, and coastal type, under which nourishments have been applied. These insights inform a Nourishment Suitability Assessment Model (NSAM), which evaluates future nourishment potential based on four key factors: coastal type, policy context, sediment availability, and prior experience. We then project shoreline retreat by combining ensemble-based sea-level rise scenarios with ambient erosion trends derived from multi-decadal satellite imagery. The analysis applies the Bruun Rule with spatially variable coastal slopes and probabilistically combines sea-level rise-induced retreat with ambient trends. Applied to over 27000km of sandy coastline, this produces spatially explicit retreat projections that are intersected with exposure data to identify high-risk beaches.

Our results show that over 98% of transects are projected to erode under sea-level rise by 2100, with median shoreline retreat reaching -80m under SSP5-8.5. In contrast, ambient change alone shows strong regional variation, with 41% of historically unstable coasts eroding but a median accretion of 17m at the European scale. Combined projections indicate that while 85% of European sandy coasts are projected to erode by mid-century under SSP2-4.5, only 11.6% of these coincide with direct infrastructure exposure. By focusing on high-risk beaches, defined as stretches with over 1km of exposed assets, this research identifies up to 841 exposure hotspots (covering 1497km) under SSP5-8.5 in 2100, helping to prioritise sites in need of adaptation. Among these exposed sites, nourishment suitability varies considerably, shaped by both physical conditions and institutional capacity. The NSAM’s traffic light classification offers a first-order indication of where nourishment could form part of context-specific adaptation strategies, with suitability highest where conditions align with historical precedent and institutional barriers are low.

Key uncertainties are identified, particularly in slope representation and the assumed independence between ambient and sea-level rise-induced retreat. These highlight priorities for future model refinement. The framework demonstrates how integrated hazard, exposure, and adaptation assessment can enable more targeted and context-specific coastal management. By synthesizing forward-looking erosion risk with backward-looking adaptation practice, this work helps bridge the gap between impact assessment and action, showing that while many coasts are at risk, not all are equally suitable for nourishment, and a context-specific approach is necessary.