Informing Management of the Nearshore and Continental Shelf
Sediment on the seafloor moves in response to a force created by the combined action of tides, ocean waves, and wind-driven currents. Sediment movement influences habitat for plants and animals, affects construction of facilities for development for offshore energy, causes suspension of contaminants such as oil that adhere to sediment particles, and shapes the seafloor.
The Massachusetts Office of Coastal Zone Management (CZM) was interested in linking this force—called bottom shear stress—to seafloor habitats, while the Bureau of Ocean Energy Management (BOEM) could use these data to inform offshore wind energy development. Motivated by these needs, the CMHRP evaluated the strength and variability of bottom shear stress, frequency of sediment movement, and their driving processes (waves vs. currents) across the continental shelf.
USGS Sea Floor Stress and Sediment Mobility Database was subsequently developed. Numerical model output is used to assess bottom shear stress over large areas of the continental shelf, then combined with grain size data to evaluate sediment mobility patterns. Output from the U.S. Integrated Ocean Observing System (IOOS), a national-regional collaboration coordinated through NOAA, was augmented with new simulations and sediment texture data from the CMHRP usSEABED program to create the database. These are the first estimates of the shelf-wide distribution of bottom shear stress and sediment mobility on a regional basis.
The Sea Floor Stress and Sediment Mobility Database also advanced rapid data dissemination protocols. Standards for data processing were established, reviewed, and approved according to USGS standards, allowing new data to be processed and released quickly in response to user needs. This strategy allowed results for each region to be made available online as soon as completed and to add data based on user requests.
CMHRP expertise and the techniques developed for the Sea Floor Stress and Sediment Mobility Database were later used to inform cleanup of the Deepwater Horizon (DWH) oil spill. During the disaster, sand and oil agglomerates (SOAs), a type of tarball that sinks rather than floats, formed over widespread areas in the surf zone of the northern Gulf of Mexico. Little research had been done on SOA dynamics, and the lack of understanding impeded cleanup efforts. In 2012, the DWH Federal On-Scene Coordinator (a representative of the U.S. Coast Guard) formed an Operational Science Team, including CHMRP researchers, to address the gaps.
The CMHRP team modified, applied, and extended the techniques developed for the Sea Floor Stress and Sediment Mobility Database to predict the mobility, seafloor interaction, and longshore transport of SOAs. The results included determining that burial and exhumation are key processes that can result in SOA appearance in previously cleared areas, predicting long-term redistribution patterns and identifying inlets as SOA traps. These findings were presented to the U.S. Coast Guard during spill response and were published in a scientific journal article. CMHRP sand and oil agglomerate research has continued in order to fill gaps identified in understanding of mixed-size particle dynamics, including SOAs, cobble/sand beaches (such as those prevalent in the Northeast), buried ordinance, and other contaminants.
Efforts to improve predictive capability for centimeter-scale particle transport and seafloor interaction will enhance the response to future oil spills and help fill other needs of the Nation, such as predicting the response of mixed-grain beaches to hurricanes and nor’easters. The CMHRP continues to directly inform the management community through continued maintenance of the USGS Sea Floor Stress and Mobility Database and through direct communication about SOA tools and findings to responders such as U.S. Coast Guard, Environmental Protection Agency, and state and local entities.
Informing Management of the Nearshore and Continental Shelf
Sediment on the seafloor moves in response to a force created by the combined action of tides, ocean waves, and wind-driven currents. Sediment movement influences habitat for plants and animals, affects construction of facilities for development for offshore energy, causes suspension of contaminants such as oil that adhere to sediment particles, and shapes the seafloor.
The Massachusetts Office of Coastal Zone Management (CZM) was interested in linking this force—called bottom shear stress—to seafloor habitats, while the Bureau of Ocean Energy Management (BOEM) could use these data to inform offshore wind energy development. Motivated by these needs, the CMHRP evaluated the strength and variability of bottom shear stress, frequency of sediment movement, and their driving processes (waves vs. currents) across the continental shelf.
USGS Sea Floor Stress and Sediment Mobility Database was subsequently developed. Numerical model output is used to assess bottom shear stress over large areas of the continental shelf, then combined with grain size data to evaluate sediment mobility patterns. Output from the U.S. Integrated Ocean Observing System (IOOS), a national-regional collaboration coordinated through NOAA, was augmented with new simulations and sediment texture data from the CMHRP usSEABED program to create the database. These are the first estimates of the shelf-wide distribution of bottom shear stress and sediment mobility on a regional basis.
The Sea Floor Stress and Sediment Mobility Database also advanced rapid data dissemination protocols. Standards for data processing were established, reviewed, and approved according to USGS standards, allowing new data to be processed and released quickly in response to user needs. This strategy allowed results for each region to be made available online as soon as completed and to add data based on user requests.
CMHRP expertise and the techniques developed for the Sea Floor Stress and Sediment Mobility Database were later used to inform cleanup of the Deepwater Horizon (DWH) oil spill. During the disaster, sand and oil agglomerates (SOAs), a type of tarball that sinks rather than floats, formed over widespread areas in the surf zone of the northern Gulf of Mexico. Little research had been done on SOA dynamics, and the lack of understanding impeded cleanup efforts. In 2012, the DWH Federal On-Scene Coordinator (a representative of the U.S. Coast Guard) formed an Operational Science Team, including CHMRP researchers, to address the gaps.
The CMHRP team modified, applied, and extended the techniques developed for the Sea Floor Stress and Sediment Mobility Database to predict the mobility, seafloor interaction, and longshore transport of SOAs. The results included determining that burial and exhumation are key processes that can result in SOA appearance in previously cleared areas, predicting long-term redistribution patterns and identifying inlets as SOA traps. These findings were presented to the U.S. Coast Guard during spill response and were published in a scientific journal article. CMHRP sand and oil agglomerate research has continued in order to fill gaps identified in understanding of mixed-size particle dynamics, including SOAs, cobble/sand beaches (such as those prevalent in the Northeast), buried ordinance, and other contaminants.
Efforts to improve predictive capability for centimeter-scale particle transport and seafloor interaction will enhance the response to future oil spills and help fill other needs of the Nation, such as predicting the response of mixed-grain beaches to hurricanes and nor’easters. The CMHRP continues to directly inform the management community through continued maintenance of the USGS Sea Floor Stress and Mobility Database and through direct communication about SOA tools and findings to responders such as U.S. Coast Guard, Environmental Protection Agency, and state and local entities.