The index was built using the Coastal Vulnerability Model within the open-source InVEST software suite, developed by the Natural Capital Project at Stanford. Seven variables feed into the calculation: shoreline type, topographic relief, the presence of protective coastal habitats, wind exposure, wave energy, storm surge and the rate of sea-level rise. Each variable is ranked on a one-to-five scale, and the final exposure value is computed as the geometric mean of the seven ranks. The researchers chose this multiplicative approach deliberately, because an additive index could allow a high score in one variable to mask low scores elsewhere, potentially hiding genuine danger. The geometric mean ensures that a coastline must score poorly across multiple dimensions before it can be labelled highly exposed.

The underlying data are among the most detailed ever assembled for the Irish coast. Wind and wave conditions were drawn from thirty years of records spanning 1995 to 2024, using the Copernicus CERRA reanalysis at 5.5-kilometre resolution and the NWSHELF wave physics reanalysis at 1.9 kilometres — both considerably finer than the global datasets often used in such studies. Storm surge and sea-level rise rates came from CMIP6-based Copernicus climate projections, while relief was calculated from a 10-metre national digital terrain model derived from LiDAR and camera sensors. Notably, the team found that the default storm surge proxy built into the InVEST model, which estimates surge from the distance to the edge of the continental shelf, correlated negatively with properly modelled surge levels around Ireland. They replaced it with hydrodynamically modelled surge data, a methodological correction that materially changed the results.

The headline finding is that exposure is not a simple story of a wild, storm-battered west versus a sheltered east. The west coast does record the highest absolute exposure values and the largest total extent of Very High Exposure coastline — Mayo alone contains 414.5 kilometres of it, with Galway County and Donegal contributing another 36 percent of the national total between them. But when exposure is measured as a proportion of each authority’s own shoreline, the picture inverts dramatically. Leitrim, with just 5.5 kilometres of coast, sees 68 percent of it classified as Very High Exposure. Meath records 57 percent of its 11 kilometres in the High Exposure band. Eastern local authorities including Dublin City, Dún Laoghaire–Rathdown, Fingal, Louth, Wexford and Wicklow hold some of the highest proportional exposure in the country, a consequence of soft, erodible Quaternary sediments and low-lying terrain rather than Atlantic storm tracks.

One of the study’s most consequential results concerns the protective role of coastal habitats. The researchers mapped four habitat types — dunes, machair, saltmarsh and seagrass — and found that 38 percent of Ireland’s coastline, some 3,299 kilometres, sits within the potential protective distance of at least one of them. Saltmarshes exert the widest influence, with over 5,000 kilometres of coast lying within 500 metres of a saltmarsh of some kind. To quantify what these ecosystems actually do, the team ran a counterfactual no-habitat scenario in which every coastal point was assigned the worst possible habitat rank. The difference was stark: in Dublin City the share of Very High Exposure coastline jumped by 15 percentage points to 29.5 percent, in Meath it rose to 89 percent, and in Galway City to 64 percent. In Fingal, the removal of habitats pushed more than 7,000 additional residents into the highest exposure zone.

The population analysis relied on a dasymetric mapping technique rather than coarse census blocks, distributing 2022 census data according to the locations of individual residential buildings at 100-metre resolution. Voronoi polygons were then used to attribute populations to their nearest coastal exposure category at buffer distances of 125, 250 and 500 metres. The results show that roughly 308,000 people live within 500 metres of the Irish coastline, and that in Dublin City and Galway City almost 10,000 residents each live within 500 metres of a Very High Exposure shoreline. In Galway City, that figure represents about 11.4 percent of the entire urban population. The vulnerability of the city was underlined in January 2025, when Storm Éowyn drove a 2.6-metre surge into Galway Bay that narrowly missed causing widespread flooding only because it coincided with a mid-tide.

Cultural heritage emerges as a second, quieter casualty. Of the 8,871 registered national monuments within 500 metres of the coast, 1,797 — one in five — fall within Very High Exposure zones, concentrated along the west and northwest. Sligo alone accounts for 383 of these sites, including the uninhabited island of Inishmurray, which holds a medieval monastic settlement and 132 registered monuments, from inscribed cross stones to leachts, the stone sepulchral monuments of early Christian Ireland. In the no-habitat scenario, the number of exposed heritage sites rises to 2,118, with the steepest proportional increases in Wexford and Fingal. Middens — ancient refuse heaps that preserve evidence of millennia of coastal life — are the most common monument type in the danger zones, a reminder that the eroding edge of Ireland is also its longest-running archaeological archive.

The team did not simply publish the index; they stress-tested it. A leave-one-out sensitivity analysis showed that removing shoreline type produced the largest shift in results, confirming that substrate erodibility is the dominant control on exposure, particularly along the east coast. Removing habitats produced the smallest overall change, which the authors attribute to the heavily modified nature of much of the Irish shoreline. They also compared four statistical methods for ranking continuous variables — quintiles, equal intervals, Jenks natural breaks and geometric intervals — and found that the choice matters enormously. Equal-interval classification collapsed the national Very High Exposure category to just 97 points, none of them on the east coast, effectively erasing the risk profile of counties that are known to be eroding fastest. The quintile approach, the model’s default, was vindicated for skewed variables such as wind, waves and relief, though the authors caution it may be less suitable for spatially uniform quantities like sea-level rise.

The findings arrive at a moment when Irish coastal policy is in flux. The Office of Public Works has completed national flood mapping and erosion projections, but no prior assessment had combined hazard characterisation with the exposure of people, ecosystems and heritage in a single framework. The new index aligns closely with independent evidence: 81 percent of points within OPW-identified wave overtopping zones rank as High or Very High Exposure, and 83 percent of segments experiencing high erosion rates in the Geological Survey Ireland shoreline change study fall into the same categories. The study also documents the cost of habitat degradation. At Rossbeigh beach in Kerry, vegetated dune cover fell by 43.2 percent between 2001 and 2019, while the Maharees Peninsula — 92 percent of which the index classifies as High or Very High Exposure — has recorded average beach retreat of 0.63 metres per year over more than a century.

The authors are careful about what the index can and cannot do. It measures relative exposure, not vulnerability; it does not account for existing engineered defences, sediment dynamics, river discharge or socioeconomic adaptive capacity, and national habitat condition assessments rate many Irish dune and saltmarsh habitats as unfavourable, meaning the baseline model may overstate the protection currently on offer. Yet as a screening tool it offers something Ireland has never had: a consistent, evidence-based map of where nature already shields the coast, where it could be restored to do so, and where hard choices about holding the line, realigning or retreating will soon be unavoidable. With global mean sea levels projected to rise by as much as 1.1 metres above 1900 levels by 2100 under high-emission scenarios, and an estimated 1.1 billion euros of Irish coastal assets at stake from a single metre of rise, that map may prove one of the most consequential documents in the country’s climate adaptation arsenal.

Subject of Research: National-scale assessment of coastal hazard exposure and the protective role of coastal habitats in Ireland

Article Title: A coastal exposure index for Ireland: relative hazard exposure and the protective role of coastal habitats

Article References: Walsh, K., de Oliveira, L. M. C., Keenahan, J., & Lim, A. (2026). A coastal exposure index for Ireland: relative hazard exposure and the protective role of coastal habitats. Natural Hazards, 122(18), Article 627. https://doi.org/10.1007/s11069-026-08361-w

Image Credits: AI Generated

DOI: 10.1007/s11069-026-08361-w

Keywords: coastal exposure, Ireland, sea-level rise, coastal habitats, nature-based solutions, InVEST, storm surge, saltmarsh, sand dunes, cultural heritage, coastal erosion, climate adaptation