NOAA Office for Coastal Management Sea Level Rise Data: Coastal Flood Threshold 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 extent of coastal areas resulting from National Weather Service issued Coastal Flood Advisories.

The Coastal Flood Advisory areas are based on individual Weather Forecast Office (WFO) guidance thresholds at monitored tide stations and are

referenced to the MLLW tidal datum. 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. The process uses either two or three source datasets depending on geographic location to derive the final

inundation rasters: the Digital Elevation Model (DEM) of the area, a tidal surface model that represents spatial tidal variability, and an

interpolated threshold surface if there is significant difference between flooding thresholds between varying geographic areas (Ex: Chesapeake Bay

area). 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 MLLW tidal datum in orthometric values (North American Vertical Datum

of 1988).The interpolated threshold surface is created using the flooding threshold values found at select NOAA tide gages used by the NWS to define

flooding events.

The methods 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 and extent, not exact location, of inundation from NWS issued Coastal Flood

Advisories.

The purpose of these data is to show the potential inundation extent caused by NWS issued Coastal Flood Advisories.

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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-flood-frequency-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://coast.noaa.gov/slr;

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 may appear during Coastal Flood Advisory conditions. 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 Flood Frequency inundation extent 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://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.