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.

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

Spatial_Reference_Information:

Horizontal_Coordinate_System_Definition:

Geographic:

Latitude_Resolution: 0.0000001

Longitude_Resolution: 0.0000001

Geographic_Coordinate_Units: Decimal degrees

Geodetic_Model:

Horizontal_Datum_Name: North American Datum of 1983

Ellipsoid_Name: Geodetic Reference System 80

Semi-major_Axis: 6378137.000000

Denominator_of_Flattening_Ratio: 298.257222101

Vertical_Coordinate_System_Definition:

Altitude_System_Definition:

Altitude_Datum_Name: North American Vertical Datum of 1988

Altitude_Resolution: 0.001

Altitude_Distance_Units: meters

Altitude_Encoding_Method: Explicit elevation coordinate included with horizontal coordinates

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;

None

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 cover areas currently shown in the NOAA CSC Sea Level Rise and Coastal Flooding Impacts 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.