Accurately estimating the probability of storm surge occurrences is necessary for flood risk assessments. This research models Long Island Sound using a coupled coastal circulation and wave model (FVCOM-SWAVE) to hindcast the 44 highest storms between 1950–2018 and fitted Poisson-GPD distributions to modelled water levels and wave heights. Floodwater elevations and significant wave heights for 10% (1/10), 3% (1/30), 2% (1/50), and 1% (1/100) annual exceedance probabilities are provided for all Connecticut coastal towns. The results show that both water levels and their corresponding return intervals are higher along the western coast of Connecticut than the eastern coast, whereas significant wave heights increase eastward. Comparing our model results with those from the North Atlantic Coast Comprehensive Study (NACCS) shows that the mean NACCS results are higher for water levels and lower for significant wave heights for longer return periods. Likewise, the Federal Emergency Management Agency (FEMA) results in large errors compared to our results in both eastern and western coastal Connecticut regions. In addition to evaluating historical risks, we also added a sea-level height offset of 0.5 m for 2050 estimates in order to examine the effect of rising sea-levels on the analysis. We find that sea-level rise reduces the return period of a 10-year storm to two years. We advise periodically updating this work as improved sea-level rise projections become available.

The vulnerability framework developed by the Intergovernmental Panel on Climate Change (IPCC) defines vulnerability as a function of exposure, sensitivity, and adaptive capacity. Building off this framework, the Connecticut Institute for Resilience and Climate Adaptation (CIRCA) developed a Climate Change Vulnerability Index (CCVI) for the state of Connecticut, designed to integrate flood and extreme heat-related climate exposure with impacted socioeconomic, infrastructure, and ecological variables into a single comprehensive index that can guide resilience planning and prioritization at multiple levels. The index serves as a central component of the Resilient Connecticut project, a statewide initiative to advance climate adaptation and resilience planning through data-driven tools, community engagement, and strategies to address flood and heat risks across vulnerable communities. In this article, we detail the development of the CCVI, including earlier iterations, methodology, stakeholder engagement activities, and lessons learned that can impact resiliency planning in Connecticut. Preliminary statistical analyses, notable regional trends, data limitations, and future areas for research advancement are also discussed. The CCVI framework detailed here can be used in the process of identifying priority areas for intervention and supporting the selection and design of targeted resilience projects, and can also be adapted for other states.