Sea Level Rise Effects on Roads & Marshes


The Sea Level Rise Effects on Roads and Marshes projects is a project between CT DEEP and UConn CLEAR.

To better understand how Connecticut’s coastal area marshes and roads may respond to sea level rise (SLR), Sea Level Affecting Marshes Model (SLAMM) was applied to Connecticut’s shoreline by Warren Pinnacle Consulting, Inc. This viewer displays the model’s results for Connecticut’s 21 largest marshes and all coastal area roads. For marshes, SLAMM was run two hundred times using alternative model inputs for key model parameters, including various SLR scenarios, to produce probability based results of likely future marsh conditions. For roads, the model uses a single SLR scenario of about 4.2 feet by 2100 from the base year of 2002.


The Sea Level Rise Effects on Roads & Marshes Viewer contains all data layers for the project in a format for exploration.



The Sea Level Affecting Marshes Model (SLAMM) is a widely adopted and effective model to predict wetland response to long-term sea-level rise and has been applied in every coastal  state in the U.S. However, as with any model’s attempt to predict change within a complex natural system, it’s important to understand the model’s limitations.

  • One important potential limitation is the uncertainty associated with some of model input parameters, such as sea level rise rates. SLAMM used the best available regionally adjusted range of rates available at the time the model was run in 2016.
  • SLAMM is not a hydrodynamic model that considers rates of water flow or ecological feedback mechanisms.
  • Land cover data used to distinguish developed versus undeveloped land, factors used to identify areas capable of supporting marsh migration onto uplands, was coarser than the model’s 5-meter resolution land cover change results.
  • SLAMM likely overestimates the area of new marsh as it does not account for future development of currently undeveloped land that the model assumes will be available to accommodate marsh migration.
  • Water level information used to identify road flooding is based upon local National Oceanic and Atmospheric Administration (NOAA) tide gauge data and 2013 Federal Emergency Management Agency (FEMA) still water coastal storm surge data.
  • SLAMM's road flooding module does not currently indicate future road flooding water depths. Therefore predicted future road flooding cannot be equated with road access/egress restrictions.
  • SLAMM is a general planning tool to identify areas to focus further coastal wetland and road flooding management investigations and is not intended for use for regulatory purposes
  • The model only generally estimates the effect of tidal restrictions (e.g. tide gates, culverts, etc.).
  • Restrictions to the flow of tidal water in and out of marshes by structures such as tide gates and culverts ‘mutes’ the tide’s amplitude which can influence the type and extent of coastal marsh inland of these restrictions. See the SLAMM Final Report sections 2.11.2 and 3.5 for more on how SLAMM considered the effects of tidal restrictions on marsh modeling results.