Sea Level Affecting Marshes Model Glossary

Accretion (Marsh)

The accumulation of sediments and other particulate matter deposited on the marsh surface from tidal water inundation and partially decayed marsh vegetation.


Ability of a natural system to accommodate changes in climate.

Climate Change

Any significant change in the measures of climate lasting for an extended period of time,  including major changes in temperature, precipitation, or wind patterns, among other effects, that occur over several decades or longer.

Conservation Easements

A legal agreement between a landowner and a land trust or government agency that permanently limits uses of the land in order to protect its conservation values.

Deterministic Model

A model whose output is fully determined by its parameters (e.g., amount of sea-level rise) and initial conditions (e.g., existing saltmarsh platform elevation). A deterministic model will always produce the same output from the same parameters and initial conditions. Contrast with the uncertainty model.

Digital Elevation Data (model)

A representation of a terrain’s surface using a regularly spaced grid of elevation points.


A functioning unit in nature that combines interacting living and non-living communities.


A semi-enclosed body of water.

Estuarine Beach

An estuarine intertidal unconsolidated shore sand or beach-bar


A semi-enclosed body of water with a connection to the open sea and within which seawater (from the ocean) is measurably diluted with freshwater derived from land drainage (e.g., the Connecticut River).

Flooded Developed Dry Land­

Upland area of impervious cover (e.g., roads, buildings),  subject to tidal flooding at least once a month that was not subject to tidal flooding in the year 2010.

Inland Fresh Marsh

Non-tidal herbaceous wetland

Inland Open Water

Non-tidally-influenced ponds, lakes, and watercourses


Area of shore between mean lower low and mean higher high water. That is, the area of shore between the elevation of the average height of the lowest low and highest high tides occurring each month.


Flooding by tidal water

Irregularly Flooded Marsh

High or brackish marsh flooded during the highest tide of the month (spring tides) with lower salinity than low or salt marsh. Dominated by salt meadow cordgrass, spike grass, and black rush.

Land Cover Classifications

System of classes or categories of what actually occupies or “covers” an area of land. For example, areas predominantly covered by the canopy of trees are classified as “forest land cover.”

Land Subsidence

Sinking of an area of land due to deep subsurface bedrock vertical movement and shallow subsurface soil compaction processes

Marsh Transgression

The upland migration of tidal marsh in response to increasing tidal water levels

Marsh Transgressions Rates

The rate at which tidal marsh migrates upland in response to increasing tidal water levels

Mean Sea level

The average height of the surface of the sea for all stages of the tide over a 19 year period, referred to as a tidal epoch.

Monte-Carlo Simulation

A computer-generated quantitative uncertainty analysis technique in which uncertain inputs in a model, for example, sea-level rise, are represented by probability distributions, instead of a single most likely value. By letting a computer recalculate model results over and over again (for example 1,000 of times), each time using different randomly selected sets of values from the (input) probability distributions, the computer uses all valid combinations of possible inputs to simulate all possible outcomes. The results of a Monte Carlo simulation are distributions of possible outcomes (rather than the one predicted outcome you get from a deterministic model); that is, the range of possible outcomes that could occur and the likelihood of any outcome occurring. This is like running hundreds or thousands of “What-if” analyses on your model, all in one go, but with the added advantage that the ’what-if’ scenarios are generated with a frequency proportional to the probability of their occurring.

Regularly Flooded Marsh

Low or salt marsh flooded daily by tidal waters and dominated by saltwater cordgrass

Relative Sea Level Rise

Increase in mean sea level relative to the vertical change in the elevation of the land.


The capacity of a site to remain viable and adapt to climate change while still maintaining diversity, but does not assume that all species currently located at these sites will necessarily be the same species present in the future.

Riverine Tidal

Watercourse whose water surface elevation is influenced by  the rise and fall of the tide

Rocky Intertidal

Rock dominated shore subject to the rise and fall of the tide.


A measure of the salt concentration of water, usually measured in parts per thousand (ppt). Higher salinity means more dissolved salts.

Sea-Level Rise

The long-term increase in mean sea level.

SLAMM Viewer

A Web-based mapping application used to present the LIS SLAMM project results.


Sea Level Affecting Marshes Model (SLAMM) is a computer model that simulates the dominant processes involved in wetland conversions and shoreline modifications during long-term sea-level rise. Mapped distributions of wetlands are generated under alternative accelerated sea-level rise scenarios.


Nontidal wetland dominated by forested or scrub-shrub vegetation.

Tidal Flat

Gently sloping estuarine intertidal mud generally devoid of vegetation

Tidal Fresh Marsh

Tidal river freshwater emergent non-woody or herbaceous plant community typically supporting a more diverse plant assemblage than salt or brackish marsh.

Tidal Marshes

A wetland subject to tidal inundation dominated by grasses, rushes, and sedges, collectively called graminoids.

Tidal Swamp Scrub Shrub

Tidally influenced swamp dominated by short, woody vegetation.

Tide Range

The difference in elevation between mean high water and mean low water.


A description of the size, shape, and elevation of a land surface

Transitional Salt Marsh

Intertidal scrub-shrub-dominated plant community frequently found at the upland border of estuarine tidal marshes (see graphic of idealized zonation of a LIS saltmarsh)

Uncertainty Model/Analysis

A model whose output may vary, reflecting inherent randomness in the process being modeled and in the model parameters (e.g., sea-level rise). Model outcomes are often expressed in terms of probability distributions or “likeliness” of occurring.


Transitional zones between terrestrial and aquatic systems where the water table is usually at or near the land’s surface or where the land is either permanently or periodically covered with water. They generally contain poorly drained hydric soils and frequently support plants adapted to wet conditions

Wetland Boundary Elevation

The boundary between coastal wetlands and drylands (including non-tidal wetlands) approximated by the highest tidal water inundation elevation level occurring once every 30 days.

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