APPLICATIONS OF THE USGS USSEABED MARINE SEDIMENT DATABASE FOR REGIONAL-SCALE GIS MAPPING OF U.S. INNER CONTINENTAL SHELF REGIONS

Explosive population growth in the coastal zone continues, placing more development at increasing risk. With the prospects of global climate change, coastal regions will be more dynamic. Beach nourishment is used to mitigate erosion, reduce storm and flooding risk, enhance recreation, and restore ecosystems. For beach nourishment to be viable, however, large volumes of quality sand are necessary. Also, the sand deposits must be located close to the beaches being nourishment and in water depths ranging typically from ~10 m to 40 m. Continental shelf regions, products of complex geologic history and dynamic processes, contain submerged landforms that provide a variety of natural functions and societal benefits. Continental margins also contain unconsolidated hard-mineral deposits such as sand and gravel that are regarded as potential aggregate resources. Sand bodies on the inner continental shelf are often the most attractive sand sources for beach nourishment. Demand for offshore sand and gravel is likely to increase in the near future. In addition, growing shortages of onshore supplies of aggregate in some parts of the country might be met using marine aggregates. However, for many regions offshore aggregates are sparse or unknown, and sand volumes are uncertain. Because offshore areas of the are increasingly important for a variety of purposes, knowledge of the framework geology and processes is critical and comprehensive databases are needed. Products of greatest value are GIS base maps displaying thematic information such as seafloor physiography, geology, sediment character and texture, seafloor roughness, and geotechnical engineering properties. Digital geologic maps, based on unified national datasets showing the sedimentary character of continental margins, are critical for scientists to better understand and interpret the geologic history and sedimentary processes that formed and continue to modify the sea floor. The USGS is leading a program to gather existing marine geologic data into the usSEABED system. This new data base is being used to conduct regional-scale assessments of offshore sand and gravel resources and to produce GIS maps to serve a variety of needs. Sand and gravel assessments and GIS mapping are in-progress offshore New York, New Jersey and Louisiana. Similar assessments are planned for other regions.