Global cost analysis on adaptation to sea level rise based on RCP/SSP scenarios

Low-lying areas are the most vulnerable to sea level rise (SLR) due to climate change in the future. In order to adapt to SLR, it is necessary to decide whether to retreat from vulnerable areas or to install dykes to protect them from inundation. Therefore, cost- analysis of adaptation using coastal dykes is one of the most essential issues in the context of climate change and its countermeasures. However, few studies have globally evaluated the future costs of adaptation in coastal areas. This study tries to globally analyze the cost of adaptation in coastal areas. First, global distributions of projected inundation impacts induced by SLR including astronomical high tide were assessed. Economic damage was estimated on the basis of the econometric relationship between past hydrological disasters, affected population, and per capita GDP using CRED's EM-DAT database. Second, the cost of adaptation was also determined using the cost database and future scenarios. The authors have built a cost database for installed coastal dykes worldwide and applied it to estimating the future cost of adaptation. The unit costs of dyke construction will increase with socio-economic scenario (SSP) such as per capita GDP. Length of vulnerable coastline is calculated by identifying inundation areas using ETOPO1. Future cost was obtained by multiplying the length of vulnerable coastline and the unit cost of dyke construction. Third, the effectiveness of dyke construction was estimated by comparing cases with and without adaptation.As a result, it was found that incremental adaptation cost is lower than economic damage in the cases of SSP1 and SSP3 under RCP scenario, while the cost of adaptation depends on the durability of the coastal dykes.