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: http://www.coast.noaa.gov/slr These data depict the potential inundation of coastal areas in Hawaii resulting from a projected 1 to 6 feet rise in sea level above 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 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 Tidal Constituent and Residual Interpolation (TCARI) methodology to combine harmonic constituents, tidal datums, and residual water level data measured at tide stations into a composite tide curve. This solution is not a NOAA/CO-OPS-generated/recognized tidal-geodetic relationship. The tidal datum values were interpolated from published values using a 2-D mathematical interpolation model that solves for weighting functions that satisfy the Laplacian. This strictly mathematical approach assumes a smooth transition of tidal characteristics and the quality control step entailed comparing the interpolated values with other known values not included in the interpolation model. This derived surface is used in lieu of NAVD88 coverage in the Hawaiian Islands for the purposes of this project. 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.

Process Steps:

• 2013-01-01 00:00:00 - The process to derive the inundation rasters and polygons and low-lying area polygons is as follows: 1. The Hawaii MHHW tidal surface dataset is derived from The Tidal Constituent and Residual Interpolation (TCARI) methodology to combine harmonic constituents, tidal datums, and residual water level data measured at tide stations into a composite tide curve. This solution is not a NOAA/CO-OPS-generated/recognized tidal-geodetic relationship. The tidal datum values were interpolated from published values using a 2-D mathematical interpolation model that solves for weighting functions that satisfy the Laplacian. This strictly mathematical approach assumes a smooth transition of tidal characteristics and the quality control step entailed comparing the interpolated values with other known values not included in the interpolation model. This derived surface is used in lieu of NAVD88 coverage in the Hawaiian Islands for the purposes of this project. Each iteration (1-6ft) 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 for each iteration (1-6ft) of slr is evaluated using an 8-sided neighborhood rule in ArcGIS using the RegionGroup tool.The largest group of connected cells is selected to create a new feature class representing hydrologically connected areas. Additional areas (groups of cells) may be selected to be included as hydrologically connected where local information exists. The remaining cells groups are analyzed to identify groups with total areas of at least 1 acre. These areas are chosen to represent unconnected 'low-lying' areas and saved as a separate layer for further analysis. 4. The rasters of hydrologically 'connected' and 'Unconnected' for each iteration of slr are converted to polygons for further analysis. (Citation: NOAA OCM Digital Elevation Models)

This data may be downloaded at: http://www.coast.noaa.gov/slr;