Strategic Spatial Prioritization of Coastal Nature-Based Solutions: A Multi-Criteria Assessment of Protective Capacity and Vulnerability along the South Korean Shoreline

Climate change–induced sea-level rise and the increasing frequency of extreme storm surges are placing increasing demands on coastal protection systems worldwide. Although conventional hard-engineering approaches have served as the primary means of coastal defence, their ecological constraints and long-term sustainability issues have become more apparent. In response, Coastal Green Infrastructure (CGI) has been explored as a nature-based approach that makes use of existing coastal features to reduce hazard exposure. In this study, we conduct a national-scale assessment of CGI potential along the coast of South Korea, where coastal form and environmental conditions differ markedly between regions.The analytical framework applied here is organised around two dimensions: Protective Benefit and Environmental Vulnerability. Together, these dimensions reflect both the capacity of coastal ecosystems to attenuate physical processes and their exposure to long-term environmental change. Six indicators were selected to represent these characteristics, including coastal landforms (tidal flats, dunes, and beaches), the distribution of blue carbon vegetation such as seagrass and salt marshes, topographic relief, wave energy conditions, and projected sea-level rise. A GIS-based analysis using a 250 m grid resolution was employed to classify the national coastline into four management types, with the aim of supporting region-specific rather than uniform coastal policies.The results indicate a clear regional contrast in CGI suitability. The West Coast (Yellow Sea), characterised by extensive tidal flats, exhibits relatively high protective capacity and low vulnerability, leading to the highest suitability classification (Type 1). By comparison, the East Coast and Jeju Island are dominated by steeper coastal profiles and higher wave energy, which limit the effectiveness of CGI when applied in isolation. In such high-energy environments, CGI is more appropriately implemented as part of a hybrid approach in combination with existing structural measures. Areas classified as Type 1 account for approximately 47.6% of South Korea’s total coastline, suggesting that a substantial proportion of the national coast may be suitable for CGI-focused management under current conditions.