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Coastal physical vulnerability to sea level rise for integrated coastal management in Santa Elena Bay in the active Ecuadorian margin

Abstract:

Santa Elena Bay (SEB) lies on Ecuador’s active convergent margin, where rapid tectonic uplift and energetic Pacific swells create a highly dynamic coast. This study presents the first Coastal Vulnerability Index assessment for Ecuador, integrating in-situ measurements, satellite products, and numerical‐model outputs to overcome the region’s sparse data. We quantified six variables: lithology, geomorphology, coastal slope, indentation, shoreline displacement, and significant wave height; and considered tidal range and relative sea-level rise qualitatively. The SEB’s coastline was ranked on a four-class scale (Low, Moderate, High, Very High). Results show a marked north–south contrast. In the Northern Zone, at least half of the shoreline registers High (15.80%) or Very High (41.76%) vulnerability, driven mainly by straight, low-lying strandplains composed of unconsolidated Quaternary sediments (57.41%), minimal indentation (63.96%), and wave heights > 0.8 m (58.69%). Erosion rates locally exceed 2 m/yr at Ayampe, Libertador Bolívar, Valdivia, and the Punta Blanca–San Pablo barrier. The Southern Zone intersperses Low and High vulnerability; Low vulnerability is associated with well-consolidated rocky headlands, whereas High vulnerability clusters at tourism hubs such as between Monteverde and San Pablo, between Punta Barandúa and Ballenita, and Salinas (east of Punta Murciélago). These findings provide the first spatially explicit baseline for SEB and highlight priority sites for intervention. They underscore the need to couple hard- and soft-engineering measures with strict land-use zoning and continuous monitoring to safeguard coastal communities, critical infrastructure, and ecosystems under ongoing sea-level rise and storm-wave impacts.