Monday, November 13, 2006

Subaqueous Landscapes and Soils within Southern New England Open Embayments.

Margot K. Payne, USDA NRCS, 1 Greenhouse Rd, 105 Coastal Institute Kingston, Kingston, RI 02881 and Mark H. Stolt, Univ of Rhode Island, 1 Greenhouse Rd, 112 Coastal Institute Kingston, Kingston, RI 02881.

Recent soil survey efforts along the Atlantic and Gulf Coasts (US states of Delaware, Florida, Texas, Maine, Maryland, and Rhode Island) have begun to include the mapping of subtidal environments in shallow water bodies.  The mapping of these “subaqueous soils” is being driven by a recognized need for an inventory of the shallow subtidal resources.  Most of the recent research on subaqueous soils has focused on shallow coastal lagoons. Thus, there is a need to expand the realm of subaqueous beyond coastal lagoons and to study embayments within larger estuarine systems. Three estuaries are being examined in this study: Little Narragansett Bay, Greenwich Bay, and Wickford Harbor. Little Narragansett Bay is a 1000 ha estuary that opens directly into the ocean. The other two sites are open embayments that open into Narragansett Bay. Bathymetric maps were created for the study areas using a fathometer and pressure sensor tide gauges to correct depths to NAVD88. On average, 13 depth soundings per hectare were recorded. Between 40 and 45 individual soil-landscape units were identified and delineated in each estuary based on slope, depth, surficial geology, and geographic location. Predominant landscape units within the bays include bay bottom, depositional shoreline platform, mainland cove, fluviomarine bottom, and submerged beach units.  Anthropogenic marina units, dredged channels, and dredge deposit shoals were also recognized.