Climate-related disasters increasingly threaten over one-third of the global population, specifical communities within 100 km of coastal zones. Indonesia, the world’s largest archipelago with the second-longest coastline, faces tidal (Rob) flooding from high tides, land subsidence, and sea-level rise. This study assess fish farmers’ vulnerability to Rob flooding in Java’s Indramayu District. Our Social Vulnerability Index (SoVI)’s development involved 150 questionnaires, focus group discussion, and key-informant interviews between 16 and 20 October 2019. It found a high vulnerability, a SoVI score of + 1.76 comprising nine principal components (PCs): external support and government mitigation, local knowledge, income, expenditure, family size, seasonal-expenditure, education, experience, and ethnicity. Contributing to ‘vulnerability’ and ‘resilience’ concepts, it highlights community memory of repeated disasters and its impact on local adaptive capacity. Findings inform policymakers to address the PCs influencing vulnerability, including critically-needed livelihood support and early-warning systems relevant to the country’s 12,000 + coastal-villages and developing countries where over 90% of fishermen live.

Aquaculture practices in developing countries, particularly Indonesia, are currently operating without effective control measures, leading to high tidal and other climate-related issues. Therefore, this study aimed to modify Coastal Vulnerability Index (CVI) assessment to evaluate the physical vulnerability of coastal areas in Indramayu Regency, West Java (62 sections) to tidal flooding (Rob). A total of 6 primary characteristics, including geomorphology, beach slope, water level rise sea, coastline alterations, tidal range, and high tide, as well as 2 additional parameters, namely land cover and mangrove breadth, were used for analysis. Based on the evaluation, CVI was divided into four groups, including (1) low, (2) moderate, (3) high, and (4) very high. The results showed that Indramayu District struggled to recover from tidal flooding, with 24.56%, 22.13%, 41.03%, and 12.28% being placed in the very high, high, moderate, and low categories. This underscored the role of local governments in improving coastal communities' capacity to respond to tidal flooding disasters. Furthermore, the results were expected to be used by local governments to enhance disaster mitigation systems, particularly for coastal areas in developing nations with comparable ecological conditions.