Sea Level Rise: Roads & Marshes Layer Information

The following data layers are part of the Sea Level Rise Effects on Roads and Marshes viewer.


The data presented here are intended for planning and/or illustrative purposes only and should not be used for determining actual jurisdictional boundaries, making regulatory decisions, developing engineering analyses/designs, etc. These maps and the data contained in them are not guaranteed to be correct or complete and conclusions drawn from such information are the sole responsibility of the user. Reasonable attempts have been made to ensure that this data and documentation is accurate and reliable; however neither the Connecticut Department of Energy and Environmental Protection, nor its partners assumes liability for any damages caused by inaccuracies in this data or documentation, or as a result of the failure of the data or software to function in a particular manner. The Connecticut Department of Energy and Environmental Protection and the University Of Connecticut make no warranty, expressed or implied, as to the accuracy, completeness, or utility of this information, nor does the fact of distribution constitute a warranty.

Data Layer List

Marsh Layers

Initial Boundary (2010)
Marsh Boundaries (separate layers for 2055, 2085, 2100)
New Marsh Boundaries (separate layers for 2055, 2085, 2100)
New Marsh Probability (separate layers for 2055, 2085, 2100)
New Marsh - High Probability (separate layers for 2055, 2085, 2100)
High Marsh (separate layers for 2055, 2085, 2100)
Marsh Loss (separate layers for 2055, 2085, 2100)

Road Layers

Road Flooding (separate layers for 2010, 2025, 2040, 2055, 2085)
All Roads in the coastal area
State Roads Only in the coastal area


Soil Suitability for Marsh Migration

Base and Boundary Layers

Marsh Names
Impervious Surface 2012   Metadata | Info

Open Space
Parcels for Protected Open Space Mapping   Data Guide | Metadata
Protected Open Space    Data Guide | Metadata
DEEP Property   Data Guide | Metadata

Base Imagery:  Info
2016 Coastal Summer 0.5ft   Metadata
2016 Statewide Spring 3 inch   Metadata | Info
2010 Coastal Summer 1ft    Metadata
2005 Coastal Summer 1ft IR    Metadata
2004 Coastal Summer 0.5m    Metadata
2004 Coastal Summer 0.5m IR    Metadata
1934 Coast

Data Layer Information

Initial Marsh Boundary

Definition: The initial boundaries of Connecticut's 21 largest marshes in 2010. The layer is in the viewer twice - once as an outline on the top of the later list and once has a filled polygon at the bottom of the layer list.

Methods: The SLAMM marsh probability layer was used with the DEEP Critical Habitats layer (metadata, data guide, resource guide), current aerial imagery and XXX to delineate the extent of the initial conditions of the 21 marsh study sites.

 Map Service    Layer Names: Initial Boundary (2010), Initial Area (2010)

Marsh Boundary (2055, 2085, 2100)

The boundary of total marsh at that year. Total marsh includes existing marsh (2010) and any new marsh since 2010 (initial marsh). High marsh is also included in total marsh.


 Map Service    Layer Names: Marsh Boundary 2055, Marsh Boundary 2085, Marsh Boundary 2100

New Marsh

For 2055, 2085 and 2100, New Marsh identifies areas of marsh that were not marsh in 2010. This means that, for example, the 2085 new marsh layer includes new marsh identified in 2055 AND 2085.


Any area with a probability greater than 0 of being New Marsh on or before that given year is included in the New Marsh Boundary.


New Marsh probability displays how likely (in percent probability) it is that new marsh will actually occur by that date. There are four categories with 67-100% being the most likely (dark green) and 1-33% (lightest green) being less likely.

 Map Service   Layer Names: New Marsh Boundary 2055, New Marsh Boundary 2085, New Marsh Boundary 2100, New Marsh Probability 2055, New Marsh Probability 2085, New Marsh Probability 2100

New Marsh - High Probability

The layers contain single polygons at least 10 acres in size with at least some area that has at least 33% probability of becoming new marsh. The High Probability New Marsh areas are identified for 2055, 2085 and 2100 and colored based on their size in acres

 Map Service    Layer Names: High Probability New Marsh > 10 acres 2100, High Probability New Marsh > 10 acres 2085, High Probability New Marsh > 10 acres 2055

High Marsh Probability

High marsh is irregularly flooded marsh and makes up the most prevalent coastal wetland type in Connecticut. It is also the most threatened due to sea level rise. As flooding frequencies increase in high marsh, they convert to low marsh which is, by definition, regularly flooded marsh.

Any location with a high marsh probability greater than 1 was included in the high marsh layer. High marsh probability values are grouped into categories where higher values (67-100%) have a higher likelihood of being high marsh at that date than lower values (1-33%). Some existing areas of low marsh, particularly those behind tidal restrictions unable to fully drain at low tide, may be erroneously coded as high marsh.

 Map Service    Layer Names: High Marsh Probability 2055, High Marsh Probability 2085, High Marsh Probability 2100

Likelihood Marsh Loss

Definition: Areas of existing marsh in 2010 that have a 25% probability or less of being marsh in the future year are included in the likelihood of marsh loss layers.


 Map Service    Layer Names: Likelihood Marsh Loss 2055, Likelihood Marsh Loss 2085 ,Likelihood Marsh Loss 2100

Soil Suitability for Marsh Migration

Definition: As coastal saltwater moves inland and stays longer on the ground, understanding how salts are retained in terrestrial soils is key to establishing a rule-base for marsh migration as part of the Sea Level Affecting Marshes Model (SLAMM). In soils, the retention of salts is influenced by soil texture, water table depth, cation exchange capacity and extractable cation exchange capacity. The layer includes suitability classes. High suitability soils have the best combination of soil properties and characteristics for SLAMM marsh migration while low suitability soils have an adverse combination of soil properties and characteristics for marsh migration. Metadata.

 Map Service    Layer Name: Soil Suitability for Marsh Migration


Road Flooding

Road Flooding layers include only roads that belong to one of the flooding classes at that date under the medium-high flooding scenario. Roads not projected to flood are excluded. It is important to note that the SLAMM model currently does not provide road flooding depths . In some cases the road segment may simply be wet and in other cases road flooding water depths could preclude safe access and egress. Additional investigation is required to gauge the severity of future road flooding frequencies. More info.

All Roads in the Coastal Area
The Roads layer is included in the viewer to provide context to the flooded road segments. Only roads in the coastal area are included.

State Roads in the Coastal Area
The State Roads Only layer includes roads from the Roads layered that were identified as a state road. More info.

 Map Service Layer Names: Road flooding 2010, Road flooding 2025, Road flooding 2040, Road flooding 2055, Road flooding 2085, Roads, State Roads Only