The bathymetry for the Great Lakes was obtained from NOAA National Centers for Environmental Information. Lake bottom slope and relief were derived from the bathymetry. Combining the bathymetry and relief in classes we created 24 classes of hydrogeoforms based on the concepts in Hammond’s Landforms to identify features on the lake bottom. Known reef locations in the Great Lakes were compiled from various sources including USGS publications and Geographic Names Information System (GNIS).
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Shoreline classifications have been compiled from NOAA’s Environmental Sensitivity Index and Environment Canada’s Environment Sensitivity Atlas. Lake Erie and portions of Lake Michigan’s shoreline classification do not exist in geospatial digital form, so the U.S. Army Corps of Engineers (USACEs) shoreline descriptions from the 2012 oblique imagery were also included. USACEs and Environment Canada geomorphology classification includes descriptions of protection, nearshore, and geomorphology. USACEs and NOAA light detection and ranging (LiDAR) for the U.S. coastal areas of the Great Lakes a portions of the northshore of Lake Ontario. Metrics were derived from the LiDAR including contours, slope, relief, and bottom roughness. Shoreline sinuosity was calculated using the shoreline delineation compiled for the Great Lakes Hydrography Dataset. The GLHD shoreline was divided into 1km segments and sinuosity was calculated.
Substrate for the bottom of the Great Lakes in the offshore regions was digitized from peer reviewed publications. In the coastal and nearshore zones, the USACEs shoreline material descriptions (2012) were extended to 30 m of depth and confirmed by researchers across the Great Lakes and benthic sampling data. In Lake Erie, the Lake Erie Habitat Task Group has collected fine scale substrate data from tow, grab sample, and underwater video data to support management decisions for fish habitat. Several other locations included fine scale substrate data such as the Illinois waters of Lake Michigan, and in the nearshore areas of Minnesota, Lake Superior.