Application of the Sea-Level Affecting Marsh Model to Coastal Connecticut

To help the state better understand climate change’s impacts on Connecticut's coast, Connecticut's Department of Environmental Protection (DEEP) and the New England Interstate Water Pollution Control Commission applied the Sea-Level Affecting Marsh Model (SLAMM)

The primary product of this work is a suite of GIS layers which include percent-likelihood maps. These maps illustrate the probability of land conversion in specific regions and can be used to inform future management decisions. This report, which offers a summary of the project as a whole, also describes the model and its many potential applications. This includes informing environmental and drinking water management plans, as well as informing infrastructure and transportation planning.

SLAMM’s capacity to show results in very high resolution can also be useful in illustrating the potential effects of sea level rise for specific localities. According to CT DEEP, SLAMM project data can support planning efforts by identifying potential future locations of new coastal marsh currently occupied by undeveloped dry upland, how current coastal high marsh/low marsh composition ratios are expected to change, and how changes in the frequency of tidal and storm surge road flooding can inform Connecticut’s coastal infrastructure resilience planning.

The report also addresses the model’s limitations, some of which stem from the exclusion of some anthropogenic changes (construction of levees, beach nourishment, and shoreline armoring) and the model’s inability to account for natural phenomena, like large storms and possible peat collapse from increased salinity.

In addition to illustrating potential scenarios through the use of GIS maps, the report also includes information about the model’s underlying land cover conversion rules, in Appendix C. A table indicates what underlying assumptions the model uses to predict transitions, for example the model converts inland fresh marshes to transitional salt marshes under an inundation scenario. If significant erosion is modeled, however, the same land type would be converted to a tidal flat. Appendix D addresses the need for additional features  to increase accuracy and better inform planning efforts. These include adding geo-spatial layers to reflect the built environment and finding ways to illustrate hydro-connectivity to more accurately represent inundation and better inform future planning efforts.

This project was funded by the Environmental Protection Agency and carried out in partnership with the Long Island Sound Study and the New England Interstate Water Pollution Control Commission.


Publication Date: February 2015

Related Organizations:

  • Connecticut Department of Energy and Environmental Protection (CT DEEP)
  • New England Interstate Water Pollution Control Commission

Related Resources:


Resource Category:

Resource Types:

  • Case study
  • Mapping tool
  • Modeling tool

States Affected:


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