Data Management Plan

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 a projected 0.5 to 10 feet rise in sea level above current Mean Higher High Water (MHHW) conditions in half foot increments. 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 for each iteration of sea level rise: 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 for each sea level rise amount above MHHW. 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 the sea level rise amount and may also flood.

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

Process Steps:

• 2023-01-01 00:00:00 - The process to derive the inundation rasters and polygons and low-lying area polygons is as follows: 1. A tidal surface is generated using NOAA VDATUM tool and various spatial interpolation/extrapolation routines, dependent upon the area being mapped. The surface generated represents the spatial variability of offsets between MHHW, a tidal datum and NAVD88, an orthometric datum. Each iteration (0.5-10ft) of slr is added to this base surface and subsequently used for mapping. 2. Using the DEM and the tidal surface (for each iteration of slr), raster calculations are made using ArcGIS Spatial Analyst Raster Calculation tool to generate multiple rasters, one 32-bit floating point raster representing depth of inundation and one 8-bit single value raster representing the extent of inundation. 3. The hydrologic connectivity of the single value raster is evaluated using an 8-sided neighborhood rule in ArcGIS using the Region Group tool. The output raster from this process is then used to create a "hydro-connected" raster for further analysis and data creation. The output raster is also used to create data representing unconnected 'low-lying' areas that are below the water surface. For more information, see the detailed mapping methods at https://coast.noaa.gov/digitalcoast/tools/slr.html. (Citation: NOAA OCM Digital Elevation Models)

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