High-resolution bathymetry is critical for mapping the surficial geology of the seafloor, identifying critical habitats, and assessing marine mineral resources such as sand and gravel. In 2016, a high-resolution bathymetry map was developed for the western Gulf of Maine (WGOM) utilizing all available multibeam echosounder (MBES) surveys, as well as several older extant surveys (Western Gulf of Maine Bathymetry and Backscatter Synthesis, Ward et al., 2016). As part of that effort, a backscatter mosaic also was developed for a subset of the MBES surveys. The backscatter synthesis did not include all of the MBES surveys due to low quality of some of the mosaics and limitations of combining MBES backscatter surveys (e.g., different frequencies).

In order to extend the high-resolution bathymetry coverage of the U.S. Northeast (NE), the WGOM Bathymetry and Backscatter Synthesis was substantially expanded. A careful review of the available bathymetry and backscatter from Maine to New York was conducted and the needed databases obtained. In addition, bathymetric lidar surveys were gathered, primarily in the WGOM. Unfortunately, the MBES coverage was relatively sparse over large areas of the NE region with few surveys available for mid and northern Maine, south of Cape Cod, and along the Atlantic coast of Long Island to New York Harbor. However, relatively good coverage exists for Long Island Sound. Similarly, high quality backscatter mosaics co-registered with the bathymetry was sparse. Nevertheless, the available bathymetry and backscatter does allow a significant expansion of the overall coverage and exposes areas where more information would be beneficial. Some low-resolution bathymetry data (e.g., single beam surveys that leave gaps between survey lines) were also obtained but were only used in a Regional Bathymetry Map.

The “Northeast Bathymetry and Backscatter Compilation: Western Gulf of Maine, Southern New England, and Long Island Sound” expands the coverage of high-resolution MBES to include southern New England and Long Island Sound. The main bathymetry synthesis is gridded at 4m, 8m, and 16m. Also included are MBES bathymetry surveys that provide more detail of regions where research projects have been conducted by the University of New Hampshire (UNH) Center for Coastal and Ocean Mapping/Joint Hydrographic Center (CCOM/JHC). The overall backscatter coverage for the WGOM inner continental shelf is presented as compilations and individual survey mosaics (UNH CCOM/JHC surveys). South of Cape Cod to New York Harbor the backscatter is limited and presented as individual surveys where available.