EarthWorks Geospatial Catalog

Hard/Complex Seafloor (250-meter grid spacing)

This dataset represents hard/complex seafloor, characterized as any combination of the following: 1) areas of exposed bedrock or concentrations of boulder, cobble, or other similar hard bottom distinguished from surrounding unconsolidated sediments, 2) a morphologically rugged seafloor characterized by high variability in bathymetric aspect and gradient, or 3) man-made structures, such as artificial reefs, wrecks, or other functionally equivalent structures that provide additional suitable substrate for development of hard bottom biological communities. On a project-specific basis, proponents may be responsible for the data and analysis to delineate hard/complex bottom, pursuant to Secretary scoping requirements in the MEPA process. Guidance will be developed by the EEA Ocean Team to further define this SSU and how it should be identified by proponents on a project-specific basis. Issues to be addressed will include descriptions of scale, biogenic reefs, definitions of terms (e.g., cobble), biological communities with vertical relief, and energetic stability. For the ocean management plan, EEA created a map of hard/complex bottom by combining three data sources. First, a statewide bathymetry data set was created by combining the highest resolution bathymetric data sets available and then calculating rugosity, a measure of bathymetric heterogeneity. Highly rugose areas were then combined with seafloor delineated as hard bottom in USGS interpreted seafloor maps. Finally the combination of these two data sets were added to points coded as hard bottom in an augmented usSEABED sediment database. The resultant map is representative of hard/complex bottom, in that it is based upon the highest resolution data available, and a specific project may obtain higher resolution data for project planning purposes. To allow for consistent evaluation and comparison of a variety of datasets with distinct spatial resolutions, accuracies, and other characteristics, the Massachusetts ocean management planning area was partitioned into 250 x 250-meter grid cells, each with a unique ID. These data were converted to the planning area grid by extracting all of the cells in which the data layer occurred.
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