The National Ocean Service's (NOS) Estuarine Bathymetry is a digital raster compilation of NOS' hydrographic survey data for selected U.S. estuaries. These data provide an important piece of the mapping puzzle to those managing our Nation's valuable estuarine resources. Although bathymetric data are most commonly used to create nautical charts, they are a crucial component in many fields of marine research, and a useful enhancement for 2D and 3D mapping.
The 70 estuarine bathymetric data sets are available in 30 meter resolution. The gridded bathymetry are an interpolated data set representing the most up-to-date depth sounding information that was available at the time of publication (1998). In a few cases the most up-to-date information was surveyed more than a century ago. Although the original data are the same source data used to create Nautical Charts, these data sets should not be used for navigation.
Supporting files are also included within the compressed download files. These files list possible uses of the data, and how the data sets were created.
Estuarine Bathymetry was developed by the Special Projects Office of the National Ocean Service (NOS) in order to produce readily available bathymetry. Seventy of the approximately 130 estuaries within the conterminous U.S. are available from this site. These estuaries represent some of the Nation's most important estuaries. Those estuaries which are not included were those that had less than 80% coverage of digital sounding data needed to support detailed bathymetric processing.
In conjunction with other geographic data, bathymetric data adds another dimension to geographic mapping and modeling and can be used either as a background layer or as a 3D surface for draping thematic maps such as benthic habitats, marine organism habitats or geologic data. Bathymetric data are a critical component for hydrodynamic models and serve as the lower boundary of the water column for computing water circulation and movement. These models are necessary to understand or predict movement of oil and hazardous materials, temperature and salinity distributions, migration of animals, and modeling storm surge and tsunami effects, to name a few.
The bathymetric data are a digital gridded depth data product offered in netCDF format at 30 meter spatial resolution, derived from source soundings collected by NOS Hydrographic Surveys Division. The extent of the bathymetric data for each estuary are defined by the water boundary component of the NOS Coastal Assessment Framework's, Estuarine Drainage Area. Elevations do not extend beyond the high water line.
Source hydrographic surveys are soundings collected by NOS over the last 150 years. These data are archived and disseminated by the National Centers for Environmental Information in Boulder, CO. Bathymetric depths are vertically referenced to the local tidal datum, typically Mean Lowest Low Water (MLLW) averaged over a 19 year tidal epoch.
In addition to the bathymetric DEM data, supporting supplemental information is also available for each DEM packaged within a zipfile. Ancillary data includes images depicting the coverage of the original sounding data, a GIS-ready vector dataset depicting the spatial extent of the DEM, and several others visualiztion files.
The source depth soundings for this project were obtained from the Hydrographic Surveys Division of NOS. These surveys represent data collected from the 1840's to mid-1990's. The principle objective of hydrographic surveys is to obtain basic data for the compilation of nautical charts with emphasis on features that may effect safe navigation. Nautical charts include information beyond depth soundings, such as rocks, hazards, and maintained channels, and are updated regularly. Although the bathymetric data offered on this site are derived from the same original data sets as NOAA's Nautical Charts, these data have not been put through the same selection process that the nautical charting requires. Therefore, these data should not be used for navigation.
Since the source data are simply a sampling of points representing depth values for specific locations, the raw data are not immediately useful without interpolation. The estuarine bathymetry was derived using a Triangulated Irregular Network (TIN) interpolation process. Original data were combined with shoreline data points attributed with mean high water elevations. These composite data files were interpolated using a linear TIN process.
The resultant TIN was then rasterized at a spatial resolution of 30 meters and projected in UTM coordinates.
At this time, the NOAA National Centers for Environmental Information does not plan to produce any additional estuarine bathymetry. However, NCEI also produces integrated topographic-bathymetric DEMs for coastal locations in the United States; updated bathymetry for certain locations may be available within these products.
Available Estuarine Bathymetry Products:
Five individual product types are available for 70 selected estuaries:
30-meter Bathymetric DEM
Spatial Extent Shapefile
Google Earth Visualization Files (bathymetry and shaded relief; .kmz format)
Sounding Density Images
The extent shapefile, visualization files and density images have been packaged together; the DEM is available as a stand-alone download.