The purpose of this data viewer is to provide City of Charleston decision makers with a preliminary look at sea level rise. Data depicting the predicted levels of sea level rise was developed and provided by NOAA Coastal Services Center in Charleston, SC using 2007 and 2009 LiDAR data for Berkeley, Charleston and Dorchester counties. These data depict the potential inundation of coastal areas resulting from a projected 1 to 3 feet rise in sea level (in 0.5 feet increments) 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 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. This viewer was developed by City of Charleston GIS staff.
Use the slider bar to see how various levels of sea level rise will impact this area. Levels represent inundation at high tide. Areas that are hydrologically connected are shown in shades of blue (darker blue = greater depth).
The process to derive the inundation rasters and 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 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 RegionGroup tool. The output raster from this process is then converted to a vector polygon feature class for further analysis. Using this 'base' feature class, a new feature class is created representing hydrologically connected areas.
The data and maps in this tool illustrate the scale of potential flooding, not the exact location, and do not account for erosion, subsidence, existing stormwater improvements, or future construction. Water levels are shown as they would appear during the highest high tides (excludes wind driven tides). The data, maps, and information provided 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 data and maps in this tool are provided “as is,” without warranty to their performance, merchantable state, or fitness for any particular purpose. The entire risk associated with the results and performance of these data is assumed by the user. This tool should be used strictly as a planning reference tool and not for navigation, permitting, or other legal purposes.