The effectiveness of setback zones for adapting to sea-level rise in Croatia

The Mediterranean coastal zone is particularly vulnerable to climate-induced sea-level rise due to rapid coastal development, leading to increased flood exposure in coastal areas. In Croatia, the share of developed coastline is still lower than in other Mediterranean countries, but development has accelerated since the 1960s. Available assessments of future coastal flood risk take into account adaptation by hard structural protection measures but do not consider other options, such as retreat from exposed areas or restricting future development. In this study, we provide the first assessment of the effects of setback zones on future coastal flood impacts on national scale. We extend the flood impact and adaptation module of the DIVA modelling framework with models of restricted future development and slow retreat (managed realignment) in the form of setback zones. We apply this model to a downscaled database of coastal segments of the coastline of Croatia. We find that setback zones are an effective and efficient measure for coastal adaptation. Construction restriction and managed realignment reduce the future cost of coastal flooding significantly, especially in combination with protection. If protection and construction restriction by setback zones are combined, the future cost of coastal flooding can be reduced by up to 39%. Combining protection and managed realignment by setback zones can reduce the future cost of coastal flooding by up to 93%.