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Low Marsh at Broadkill, DE, Lower Delaware Bay, Intermediate Sea Level Rise Scenario, “Protect Developed Dry Land” model protection scenario, EPA ORD NCEA

Metadata Updated: August 30, 2023

This raster GIS dataset contains 5-meter-resolution cells depicting the areas of LOW marsh gain (value=1), lost (value=-1) and remaining (no change; value=0). Low marsh (LM) was defined as regularly flooded marsh [SLAMM category 8]. LM is normally inundated by tidal water at least once per day. Based on SLAMM simulation outputs, we generated the gain and loss map by using the “Raster Calculator” tool under “Spatial Analyst Tools” in ArcGIS software. The methodology consists of the three steps listed below (where we use low marsh [LM] as an example). The same process can be applied to other SLAMM land cover categories.

1) Open ArcMap, add SLAMM simulation raster outputs (all SLAMM categories) for baseline year and future years.

2) In Raster Calculator, set the SLAMM codeequal to8 (low marsh = SLAMM category 8) to generate a new raster. Each individual cell in the new raster is assigned a value of “0” or “1”. “1” is low marsh and “0” is any other SLAMM land cover category. Perform this step for both the baseline year and future year.

3) In Raster Calculator, subtract the new raster for the baseline year from the new raster for the future year (formula = new future year raster - new baseline year raster). The calculation generates a new raster, in which each individual cell is assigned a value of “-1”, “0”, or “1”. Based on the calculation, “-1” means low marsh loss in the future (the cell has converted from low marsh to a different SLAMM category), “0” means low marsh is remaining (the cell stays the same), and “1” means low marsh gain in the future (the cell has converted from a different SLAMM category to low marsh).

Prior SLAMM work has been performed in the Delaware Bay, but our methods differ in that we derive results for specific marsh areas and utilize more recent, higher resolution elevation data (2015 USGS CoNED Topobathy Model: New Jersey and Delaware), the most recent SLR projections, and site-specific accretion data (through 2016). These SLAMM simulations were performed as part of a larger project by the USEPA on frameworks and methods for characterizing relative wetland vulnerabilities.

Note: additional raster files from this project are available upon request. These include files from low and high SLR scenarios and different model protection scenarios. For more information, contact Jordan West (

Access & Use Information

License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

Downloads & Resources


Metadata Date May 8, 2019
Metadata Created Date August 30, 2023
Metadata Updated Date August 30, 2023
Reference Date(s) September 15, 2017 (creation), February 1, 2019 (publication), February 28, 2018 (revision)
Frequency Of Update

Additional Metadata

Resource Type Dataset
Metadata Date May 8, 2019
Metadata Created Date August 30, 2023
Metadata Updated Date August 30, 2023
Reference Date(s) September 15, 2017 (creation), February 1, 2019 (publication), February 28, 2018 (revision)
Responsible Party U.S. Environmental Protection Agency, Office of Research and Development-National Center for Environmental Assessment (Publisher)
Contact Email
Guid 9427C992-AF9F-4311-975D-46E098B6B86E
Access Constraints
Bbox East Long -75.12876
Bbox North Lat 38.867302
Bbox South Lat 38.728269
Bbox West Long -75.387382
Coupled Resource
Frequency Of Update
Harvest Object Id 8c53f7a6-0198-41c2-977a-b29737cd6bc8
Harvest Source Id 9b3cd81e-5515-4bb7-ad3c-5ae44de9b4bd
Harvest Source Title Environmental Dataset Gateway ISO Geospatial Metadata
Licence None. Please check sources, scale, accuracy, currency and other available information. Please confirm that you are using the most recent copy of both data and metadata. Acknowledgement of the EPA would be appreciated.
Metadata Language eng
Metadata Type geospatial
Old Spatial {"type": "Polygon", "coordinates": [[[-75.387382, 38.728269], [-75.12876, 38.728269], [-75.12876, 38.867302], [-75.387382, 38.867302], [-75.387382, 38.728269]]]}
Spatial Data Service Type
Spatial Reference System 4269
Spatial Harvester True
Temporal Extent Begin 2001-01-01T00:00:00
Temporal Extent End 2100-12-31T00:00:00

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