Connecticut Sea Level Rise

Figure 1: Sea level rise projections for Connecticut based on local tide gage observations (blue), the IPCC (2013) RPC 4.5 model simulations near Long Island Sound (yellow line), the semi-empirical models (orange line) and ice budgets (magenta line) as in CPO-1. (image is saved as CTSLRprojections)

Measurements of sea level by instruments in the water and satellite altimeters provide unambiguous evidence that the annual mean level of the ocean surface is rising. Coastal communities should expect that the frequency of coastal flooding will increase.

In 2012 NOAA released global sea level rise scenarios that were referenced in Connecticut state statute requiring that sea level rise be considered in state and local plans of conservation and development and natural hazard mitigation plans. NOAA report CPO-1 (Parris et al. 2012) provided four projections on sea level rise scenarios. That same statute charged UConn CIRCA with updating the scenarios to be local for the state of Connecticut. To provide more local guidance for Connecticut Sea Level Rise in Connecticut, CIRCA Executive Director and Professor of Marine Sciences, James O’Donnell authored the report, finalized in January 2019.

“Connecticut plan for the upper end of the range of values projected of sea level rise or up to 20 inches (1 foot 8 inches) of sea level rise higher than the national tidal datum in Long Island Sound by 2050 and that it is likely that sea level will continue to rise after that date.”

CIRCA has reviewed and modified the projections to include the effects of local oceanographic conditions, more recent data and models, and local land motion. A concise summary of the results are shown in Figure 1.

The Institute also recommended that the scenarios be updated at least every 10 years, or more frequently, to incorporate the best available science and new observations.

Connecticut Coastal Towns Storm Surge Annual Exceedance Probability (Return Interval) Viewer

Storm surge water level return interval plot to model the future projection of the sea levels.

Understanding the risk posed by extreme storm events and accurate assessment of the flood risk is crucial for the successful management of the coastal communities using increasing resiliency. There are only a few available tide gauge, buoy, and storm sensor data in the Long Island Sound to project the extreme sea level statistics using the observed records available to determine the level of risk along the Connecticut coastline accurately. In this work, we reproduced the highest 44 storms between 1950-2018 using a coupled circulation and wave model. The modeled events are fit to a probability distribution to statistically estimate the annual exceedance probabilities and return periods for expected storms.

The results presented here are to highlight the storm surge water levels and significant wave heights, which may contribute to a better understanding of extreme storms and guide decision-makers.

“The probability of the occurrence of the events increases with the added 20 inc local sea-level rise projections for 2050. The 10% annual probability (10-year return period) increases approximately to 50% (2-year return period), and 1% annual probability (100-year return period) increases approximately to 5% (20-year return period). The climate change impacts on the storm characteristics and sea-level rise should be considered to plan coastal projects.”

Connecticut Coastal Towns Vulnerability Assessment

Considering that local, regional, and global conditions strongly determine coastal processes and vulnerability, a good understanding of the physical, biological and social system characteristics is required, as well as climatological and hydrological data. The project is a science-based regional risk assessment that will inform the regional initiatives on adaptation priorities and spatial aspects of the coastal system response to sea-level rise. The purpose of this study is to establish resilient coastal communities through coastal vulnerability assessment that incorporates the vulnerable regions to the coastal flooding concerning the biophysical and socio-economical perspective.

The project developed a methodology to identify zones that face common challenges to climate change, and that have shared priorities in terms of coastal resilience. GIS supported index-based approach is useful to analyze in multi-scale and multi-criteria both interactively and express an overlapped one-dimensional risk index. The coastal vulnerability index demonstrates the vulnerable regions to the coastal flooding concerning the biophysical and socio-economical perspective. The index gives a relative sense of zones that are more susceptible to exposure and identify places that need to develop adaptation measures to cope with the effects of future climate scenarios.

“The coastal vulnerability mapping is proposed to identify the areas that are more susceptible to its surrounding region. This approach provides a framework for regional, municipal, and site scale planning to tackle the challenges of future sea-level rise flooding.”


Connecticut Legislation

CIRCA's final report provides the basis for sea level rise projections in Governor's Bill S.B. 7, which was introduced into the 2018 legislative session and was enacted into law as Public Act 18-82.

Senate Bill No. 7, Public Act No. 18-82

PA 18-82

Substitute Senate Bill No. 9, Public Act No. 18-50

PA 18-50

Waves in Long Island Sound: NOAA CREST Project

The goal of the research was to numerically resolve sea dynamics (such as currents, waves, sea surface displacement) at the Connecticut coastline. The estuarine circulation of the LIS mediates key biogeochemical cycles (cycles in which chemical elements and simple substances are transferred between living systems and the environment) in the region upon which local environments depend. Understanding local changes in the wave field and circulation dynamics in the LIS goes beyond purely scientific endeavors, with future implications that effect coastal communities and the natural environments. Currently, there is particular attention being placed into evaluating the risk of flooding at coastal areas as the upcoming and present challenges of climate change at a regional scale become apparent with changes in sea level and storm frequency and intensity. This work will help coastal communities better understand the effect of waves at the coastline – where people live, work, and play.

“We have modeled a set of storms that have affected the region in recent years for five locations – Hurricane Gloria, Super Storm Sandy, Hurricane Irene (2011), Nor’easter of 2015, and several strong Nor’easters. Focusing on key wave statistics such as the significant wave height and the dominant wave period.”

The model corresponds to the Finite Volume Community Ocean Model (FVCOM) and uses a 3-D unstructured grid-free surface and primitive equations to calculate the hydrodynamics. The model also combines the circulation model with a wave module as well as radiation stresses, the bottom boundary layer, and surface stress.

The point of records

The results of a wave model at five locations along the Connecticut shoreline are reported below.


Visit the buoys page for more information about the WLIS and CLIS buoys.

Wave information can be provided for any point in Long Island Sound or along its coastline. Please contact to get additional data points.

Point ID Depth (m) Latitude Longitude
15631 13.136 40.991 -73.582
18277 14.292 41.106 -73.262
16339 6.244 41.232 -72.918
12470 6.932 41.254 -72.324
8797 11.423 41.309 -71.941

The project is still undergoing to increase the number of data points.


  • U.S. Department of Commerce. National Oceanic and Atmospheric Administration. .pdf Sea Level Rise and Nuisance Flood Frequency Changes around the United States.pdf, by William Sweet et al., Technical Report NOS CO-OPS 073, NOAA. Silver Spring, MD, 2014.
  • “Summary of PA 13-179—sSB 1012: An Act Concerning The Permitting of Certain Coastal Structures By The Department of Energy and Environmental Protection” Last modified June 21, 2016.
  • CIRCA local sea level rise projections: ODonnell 2017 Technical Report Executive Summary.pdf and Presentation (with audio) and slides only.pdf.
  • CIRCA's blog, "Current Policies on Sea Level Rise in Connecticut"provides an overview of PA 13-179 and the NOAA CPO-1 report's global sea level rise projections.