Submarine groundwater discharge (SGD) into Maryland's Corsica River Estuary was investigated as part of a larger study to determine the importance of nutrient delivery to Chesapeake Bay via this pathway. Resource managers are concerned about nutrients that are entering the estuary via submarine groundwater discharge from this primarily agricultural watershed that may be contributing to eutrophication, harmful algal blooms, and fish kills. An interdisciplinary U.S. Geological Survey (USGS) science team conducted field operations in the estuary in April and May 2007. Techniques used included continuous resistivity profiling (CRP), piezometer sampling, seepage meter measurements, and collection of a radon tracer time series. Better understanding of the style, locations, and rates of groundwater discharge could lead to improved models and mitigation strategies for estuarine nutrient over-enrichment in the Corsica River Estuary, and other similar settings. More information on the field work can be accessed from the Woods Hole Coastal and Marine Science Center Field Activity webpage: https://cmgds.marine.usgs.gov/fan_info.php?fan=2007-005-FA.

Submarine groundwater discharge (SGD) into Maryland's Corsica River Estuary was investigated as part of a larger study to determine the importance of nutrient delivery to Chesapeake Bay via this pathway. Resource managers are concerned about nutrients that are entering the estuary via submarine groundwater discharge from this primarily agricultural watershed that may be contributing to eutrophication, harmful algal blooms, and fish kills. An interdisciplinary U.S. Geological Survey (USGS) science team conducted field operations in the estuary in April and May 2007. Techniques used included continuous resistivity profiling (CRP), piezometer sampling, seepage meter measurements, and collection of a radon tracer time series. Better understanding of the style, locations, and rates of groundwater discharge could lead to improved models and mitigation strategies for estuarine nutrient over-enrichment in the Corsica River Estuary, and other similar settings. More information on the field work can be accessed from the Woods Hole Coastal and Marine Science Center Field Activity webpage: https://cmgds.marine.usgs.gov/fan_info.php?fan=2007-005-FA.

A geophysical survey to delineate the fresh-saline groundwater interface and associated sub-bottom sedimentary structures beneath Indian River Bay, Delaware, was carried out in April 2010. This included surveying at higher spatial resolution in the vicinity of a study site at Holts Landing, where intensive onshore and offshore studies were subsequently completed. The total length of continuous resistivity profiling (CRP) survey lines was 145 kilometers (km), with 36 km of chirp seismic lines surveyed around the perimeter of the bay. Medium-resolution CRP surveying was performed using a 50-meter streamer in a bay-wide grid. Results of the surveying and data inversion showed the presence of many buried paleochannels beneath Indian River Bay that generally extended perpendicular from the shoreline in areas of modern tributaries, tidal creeks, and marshes. An especially wide and deep paleochannel system was imaged in the southeastern part of the bay near White Creek. Many paleochannels also had high-resistivity anomalies corresponding to low-salinity groundwater plumes associated with them, likely due to the presence of fine-grained estuarine mud and peats in the channel fills that act as submarine confining units. Where present, these units allow plumes of low-salinity groundwater that was recharged onshore to move beyond the shoreline, creating a complex fresh-saline groundwater interface in the subsurface. The properties of this interface are important considerations in construction of accurate coastal groundwater flow models. These models are required to help predict how nutrient-rich groundwater, recharged in agricultural watersheds such as this one, makes its way into coastal bays and impacts surface water quality and estuarine ecosystems. For more information on the survey conducted for this project, see https://cmgds.marine.usgs.gov/fan_info.php?fan=2010-006-FA.

A geophysical survey to delineate the fresh-saline groundwater interface and associated sub-bottom sedimentary structures beneath Indian River Bay, Delaware, was carried out in April 2010. This included surveying at higher spatial resolution in the vicinity of a study site at Holts Landing, where intensive onshore and offshore studies were subsequently completed. The total length of continuous resistivity profiling (CRP) survey lines was 145 kilometers (km), with 36 km of chirp seismic lines surveyed around the perimeter of the bay. Medium-resolution CRP surveying was performed using a 50-meter streamer in a bay-wide grid. Results of the surveying and data inversion showed the presence of many buried paleochannels beneath Indian River Bay that generally extended perpendicular from the shoreline in areas of modern tributaries, tidal creeks, and marshes. An especially wide and deep paleochannel system was imaged in the southeastern part of the bay near White Creek. Many paleochannels also had high-resistivity anomalies corresponding to low-salinity groundwater plumes associated with them, likely due to the presence of fine-grained estuarine mud and peats in the channel fills that act as submarine confining units. Where present, these units allow plumes of low-salinity groundwater that was recharged onshore to move beyond the shoreline, creating a complex fresh-saline groundwater interface in the subsurface. The properties of this interface are important considerations in construction of accurate coastal groundwater flow models. These models are required to help predict how nutrient-rich groundwater, recharged in agricultural watersheds such as this one, makes its way into coastal bays and impacts surface water quality and estuarine ecosystems. For more information on the survey conducted for this project, see https://cmgds.marine.usgs.gov/fan_info.php?fan=2010-006-FA.

The Hudson Shelf Valley is the submerged seaward extension of the ancestral Hudson River drainage system and is the largest physiographic feature on the Middle Atlantic continental shelf. The valley begins offshore of New York and New Jersey at about 30-meter (m) water depth, runs southerly and then southeasterly across the Continental Shelf, and terminates on the outer shelf at about 85-m water depth landward of the head of the Hudson Canyon. Portions of the 150-kilometer-long valley were surveyed in 1996, 1998, and 2000 using a Simrad EM1000 multibeam echosounder mounted on the Canadian Coast Guard ship Frederick G. Creed. The purpose of the multibeam echosounder surveys was to map the bathymetry and backscatter intensity of the sea floor of the valley, providing a framework for geologic, oceanographic, and geochemical studies. The data from the three surveys are combined to produce grids of bathymetry and backscatter intensity at 12-m resolution that cover the entire valley and the head of the Hudson Canyon. The mapping was done by the U.S. Geological Survey in cooperation with the U.S. Army Corps of Engineers with support from the Canadian Hydrographic Service and the University of New Brunswick.

The Hudson Shelf Valley is the submerged seaward extension of the ancestral Hudson River drainage system and is the largest physiographic feature on the Middle Atlantic continental shelf. The valley begins offshore of New York and New Jersey at about 30-meter (m) water depth, runs southerly and then southeasterly across the Continental Shelf, and terminates on the outer shelf at about 85-m water depth landward of the head of the Hudson Canyon. Portions of the 150-kilometer-long valley were surveyed in 1996, 1998, and 2000 using a Simrad EM1000 multibeam echosounder mounted on the Canadian Coast Guard ship Frederick G. Creed. The purpose of the multibeam echosounder surveys was to map the bathymetry and backscatter intensity of the sea floor of the valley, providing a framework for geologic, oceanographic, and geochemical studies. The data from the three surveys are combined to produce grids of bathymetry and backscatter intensity at 12-m resolution that cover the entire valley and the head of the Hudson Canyon. The mapping was done by the U.S. Geological Survey in cooperation with the U.S. Army Corps of Engineers with support from the Canadian Hydrographic Service and the University of New Brunswick.

The Gulf Islands National Seashore (GUIS) is composed of a series of barrier islands along the Mississippi - Alabama coastline. Historically these islands have been undergoing long-term change. The devastation of Hurricane Katrina in 2005 prompted questions about the stability of the barrier islands and their potential response against future storm impacts. Additionally, there was concern from the National Park Service (NPS) about the preservation of the historical Fort Massachusetts, located on West Ship Island. Prior to 1969, Ship Island was an individual island. In 1969 Hurricane Camille breached Ship Island, widening the cut and splitting it into what is now known as West Ship Island and East Ship Island. In July of 2007, the U.S. Geological Survey (USGS) was able to provide the NPS with a small bathymetry survey of Camille Cut using high-resolution single-beam bathymetry. This provided the GUIS with a post-Katrina assessment of the bathymetry in Camille Cut and along the northern shoreline directly in front of Fort Massachusetts. Ultimately, this survey became an initial bathymetry dataset toward a larger USGS effort included in the Northern Gulf of Mexico (NGOM) Ecosystem Change and Hazard Susceptibility Project.

Surveys of the bathymetry and backscatter intensity of the sea floor south of Long Island, New York, were carried out in November 1998 using a Simrad EM1000 multibeam echosounder mounted on the Canadian Coast Guard ship Frederick G. Creed. The purpose of the multibeam echosounder surveys was to explore the bathymetry and backscatter intensity of the sea floor in several areas off the southern coast of Long Island along the 20-meter isobath. Survey areas offshore of Fire Island Inlet, Moriches Inlet, Shinnecock Inlet, and southwest of Montauk Point were about 1 kilometer (km) wide and 10 km long. The area was mapped by the U.S. Geological Survey with support from the Canadian Hydrographic Service and the University of New Brunswick.

Surveys of the bathymetry and backscatter intensity of the sea floor south of Long Island, New York, were carried out in November 1998 using a Simrad EM1000 multibeam echosounder mounted on the Canadian Coast Guard ship Frederick G. Creed. The purpose of the multibeam echosounder surveys was to explore the bathymetry and backscatter intensity of the sea floor in several areas off the southern coast of Long Island along the 20-meter isobath. Survey areas offshore of Fire Island Inlet, Moriches Inlet, Shinnecock Inlet, and southwest of Montauk Point were about 1 kilometer (km) wide and 10 km long. The area was mapped by the U.S. Geological Survey with support from the Canadian Hydrographic Service and the University of New Brunswick.

These data were collected under a cooperative agreement with the Massachusetts Office of Coastal Zone Management (CZM) and the U.S. Geological Survey (USGS), Woods Hole Coastal and Marine Science Center (WHCMSC). Initiated in 2003, the primary objective of this program is to develop regional geologic framework information for the management of coastal and marine resources. Accurate data and maps of sea-floor geology are important first steps toward protecting fish habitat, delineating marine resources, and assessing environmental changes due to natural or human impacts. The project is focused on the inshore waters (5-30 m deep) of Massachusetts between the New Hampshire border and Cape Cod Bay. Data collected for the mapping cooperative have been released in a series of USGS Open-File Reports (http://woodshole.er.usgs.gov/project-pages/coastal_mass/). This is the spatial dataset for the Red Brook Harbor survey area within Buzzards Bay, Massachusetts. These data are the results of a high-resolution geophysical (bathymetry, backscatter intensity, and seismic reflection) and ground validation (sediment samples and bottom photographs) survey, conducted in 2009. In addition to inclusion within the USGS-CZM geologic mapping effort, these Red Brook Harbor data will be used to assess the shallow-water mapping capability of the geophysical systems deployed for this project, with an emphasis on identifying resolution benchmarks for the interferometric sonar system. (http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2009-018-FA)