Sea Level Affecting Marshes Model (SLAMM)

U.S. Fish and Wildlife Service: Brian Czech, [email protected]

SLAMM-View Application: Jeff Ehman, [email protected]

SLAMM Simulator: Jonathan Clough, [email protected]

Posted on: 3/21/2010 - Updated on: 2/27/2020

Posted by

Jennie Hoffman


Within SLAMM, there are five primary processes that affect wetland fate under different scenarios of sea-level rise:

Inundation: The rise of water levels and the salt boundary are tracked by reducing elevations of each cell as sea levels rise, thus keeping mean tide level (MTL) constant at zero.  Spatially variable effects of land subsidence or isostatic rebound are included in these elevation calculations.  The effects on each cell are calculated based on the minimum elevation and slope of that cell. 

Erosion: Erosion is triggered based on a threshold of maximum fetch and the proximity of the marsh to estuarine water or open ocean.  When these conditions are met, horizontal erosion occurs at a rate based on site- specific data.

Overwash: Barrier islands of under 500 meters width are assumed to undergo overwash at a user-specified interval.  Beach migration and transport of sediments are calculated.

Saturation: Coastal swamps and fresh marshes can migrate onto adjacent uplands as a response of the fresh water table to rising sea level close to the coast.

Accretion: Sea level rise is offset by sedimentation and vertical accretion using average or site-specific values for each wetland category.  Accretion rates may be spatially variable within a given model domain.

SLAMM-View was designed to improve comparisons of models produced through the SLAMM modeling tool (, which simulates the effects of sea level rise (SLR) over the next century on ecosystem processes in marshes and coastal ecosystems and models predicted SLR impacts, shoreline modifications, and wetland conversions. SLAMM View also enables users to view predicted impacts to roads and assess the inundation frequency of roadways under different SLR scenarios. SLAMM View provides an additional tool to compare different geospatial outputs produced through the SLAMM model and let users compare model outputs from different years, or from one year under different SLR scenarios for selected project sites where the SLAMM model has been applied. The tool also provides a summary report detailing projected changes. Users can select from different SLR scenarios: the IPCC Scenario A1B Mean (39 cm of global average SLR); the IPCC Scenario A1B Maximum (69 cm of global average SLR); and global SLR ranges from 1-2 meters eustatic SLR.

Example in use: SLAMM View provides data for projects throughout the United States at both the regional and project site scale and serves as the public access point for SLAMM outputs. For example, the Gulf Coast Prairie Landscape Conservation Cooperative (GCPLCC) ran SLR simulations for the entire U.S. Gulf Coast to support a focal species analysis. Several parts of the coast had already been examined using SLAMM but the results were not directly comparable due to different sea-level scenarios and modeling approaches used. The GCPLCC funded a project to fill gaps in the geographic coverage of SLAMM and re-running previous simulations to generate consistent scenarios from 0.5-2 m of SLR by 2100 along the entire coast. The results were then used to assess the impacts of SLR on focal species and their associated critical habitats in support of the Gulf Coast Vulnerability Assessment Project. The final data is available on SLAMM-View (

Phase of Adaptation: Awareness, Assessment, Planning, Integration, Sharing


Land managers, natural resource managers, local authorities, planners, scientists

Managing Organizations

Incorporated June 2001 in Warren, Vermont, WPC Inc. has been focused primarily with improving and implementing both the SLAMM (Sea Level Affecting Marshes Model) and AQUATOX models for various applications. Clients have included U.S.


Habitat/Biome Type
Target Climate Changes and Impacts

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