RoxAnn Acoustic Sensor Data Points - Rehoboth Bay, Delaware Algae Mapping with Single Beam Acoustics: June 12 - 16, 2000

During the spring of 1999, the Delaware Coastal Programs(DCP) identified the spatial extent of macroalgae in the shallow portions of Rehoboth Bay utilizing traditional photogrammetric methods. The DCP used true color aerial photographs, image processing software, a geographical information system (GIS), and a limited field survey to identify 1.88 square kilometers of macroalgae in all but the deepest parts of the bay. Turbid conditions prevented identification of the full extent of the vegetation.Although the 1999 effort was highly successful, it was clear that aerial photography could not penetrate to the deeper parts of the bay or where conditions were turbid.For the 2000 effort, the DCP partnered with the National Oceanic and Atmospheric Administration (NOAA) Office for Coastal Management Coastal Remote Sensing Program. The Benthic Habitat Mapping project, a part of the Center's Coastal Remote Sensing program, utilized a RoxAnn acoustic sensor to identify benthic cover in turbid areas of the bay June 12- 16, 2000.The instrument was used to identify bottom type by extracting data on bottom roughness and bottom hardness from the primary and secondary sounder echoes. The data is classified on-the-fly, using a towed video camera for field validation, and subject to a post-processing classification. The unit collected data throughout the bay in areas greater than 1.4 meters in depth and serves as a powerful complement to the aerial photography. The RoxAnn data points were exported into a geographic information system (GIS) and post-processed to remove unreliable data points and re-classified. This data set is comprised of the cleaned, attributed point data. The attributes include location, date, time, depth, field derived classification,and the classification derived from post-processing the data. This system is fully described in "Development of a System for Classification of Habitats in Estuarine and Marine Environments (SCHEME) for Florida, Report to U.S. EPA - Gulf of Mexico Program, Florida Fish and Wildlife Conservation Commission, Florida Marine Research Institute.Review Draft 12/04/02."

Original contact information:

Contact Org: NOAA Office for Coastal Management

Phone: 843-740-1202

Email: coastal.info@noaa.gov

Every year more boaters, fishers, and other recreational users place a larger strain on the limited space and natural resources of Rehoboth Bay, Delaware. At the same time, regional development, agricultural, and industrial activities impact the bay with increased runoff of chemicals and nutrients. A particular genus of macroalgae known as Ulva grows in these waters naturally, but has become an increasing problem with greater biomass due to changing water chemistry. Ulva management in Rehoboth Bay has challenged government agencies and local organizations for a number of years. Increases in Ulva biomass can lead to an increase in dead organic matter and to reduced dissolved oxygen levels in the bay. Lower dissolved oxygen can have a significant impact on the local aquatic ecology,increased dead organic loads can cause foul odors and create hazards for boats.Government agencies have funded Ulva collection operations to reduce the impacts of the macroalgae on the ecosystem and on recreational opportunities in Rehoboth Bay.Unfortunately, little data exists on the spatial extent of Ulva in Rehoboth Bay or the effectiveness of the collection operations. It seems imperative that the agencies funding the operations identify the present extent of Ulva in the bay and periodically update that information to determine the effectiveness of their efforts.

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Single beam acoustic data points (RoxAnn) collected in Rehoboth Bay, Delaware, June 12 - 16, 2000.

Not for navigation.

None

Bathymetric data has not been corrected for tide and wind variables. Not for use in navigation.

Arc/Info coverage format

This data is accurate to field conditions in June 2000. The depth points have not been corrected for tide and wind variables.

Not applicable

Not applicable

Data is complete.

The data were collected with the RoxAnn acoustic sensor in a geographic projection. The field database was exported from RoxMap software as a text file. Unreliable data points(i.e. data with impossible bathymetry) were deleted. Using ArcInfo, the point data were converted to both a shapefile and coverage, and reprojected to US State Plane Nad83, Delaware.