NOAA Office for Coastal Management Sea Level Rise Data: Current Mean Higher High Water Inundation Extent

These data were created as part of the National Oceanic and Atmospheric Administration Office for Coastal Management's efforts to create an online mapping viewer depicting potential sea level rise and its associated impacts on the nation's coastal areas. The purpose of the mapping viewer is to provide coastal managers and scientists with a preliminary look at sea level rise (slr) and coastal flooding impacts. The viewer is a screening-level tool that uses nationally consistent data sets and analyses. Data and maps provided can be used at several scales to help gauge trends and prioritize actions for different scenarios. The Sea Level Rise and Coastal Flooding Impacts Viewer may be accessed at: https://www.coast.noaa.gov/slr

These data depict the potential inundation of coastal areas resulting from current Mean Higher High Water (MHHW) conditions. The process used to produce the data can be described as a modified bathtub approach that attempts to account for both local/regional tidal variability as well as hydrological connectivity. The process uses two source datasets to derive the final inundation rasters and polygons and accompanying low-lying polygons: the Digital Elevation Model (DEM) of the area and a tidal surface model that represents spatial tidal variability. The tidal model is created using the NOAA National Geodetic Survey's VDATUM datum transformation software (http://vdatum.noaa.gov) in conjunction with spatial interpolation/extrapolation methods and represents the MHHW tidal datum in orthometric values (North American Vertical Datum of 1988).

The model used to produce these data does not account for erosion, subsidence, or any future changes in an area's hydrodynamics. It is simply a method to derive data in order to visualize the potential scale, not exact location, of inundation from sea level rise.

Both raster and vector data are provided. The raster data represent both the horizontal extent of inundation and depth above ground, in meters. The vector data represent the horizontal extent of both hydrologically connected and unconnected inundation. The vector "slr" data represent inundation that is hydrologically connected to the ocean. The vector "low" data represent areas that are hydrologically unconnected to the ocean, but are below MHHW and may also flood.

For more information, contact coastal.info@noaa.gov.

The purpose of these data is to show potential inundation from current Mean Higher High Water (MHHW) for the area.

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A detailed methodology for producing these data can be found via the following url:

https://coast.noaa.gov/data/digitalcoast/pdf/slr-inundation-methods.pdf

Any conclusions drawn from the analysis of this information are not the responsibility of the Office for Coastal Management or its partners.

This data may be downloaded at: https://www.coast.noaa.gov/slrdata

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These data illustrate the scale of potential flooding, not the exact location, and do not account for erosion, subsidence, or future construction. Inundation is shown as it would appear during the highest high tides (excludes wind driven tides) with the sea level rise amount. These data should be used only as a screening-level tool for management decisions. As with all remotely sensed data, all features should be verified with a site visit. The dataset is provided "as is," without warranty to its performance, merchantable state, or fitness for any particular purpose. The entire risk associated with the results and performance of this dataset is assumed by the user. This dataset should be used strictly as a planning reference and not for navigation, permitting, or other legal purposes.

The MHHW layer covers areas currently shown in the NOAA Sea Level Rise Viewer. The current status of areas of coverage for the tool can be accessed at: https://www.coast.noaa.gov/slr.

Standard methods for determining inundation were used. The vertical accuracy of these data is dependent on the source elevation data and the error associated with vertical datum conversions within NOAA's VDatum software.