Previous sidescan surveys performed by USACE identified areas of potential hardbottom in the nearshore environment (-5 to -30 feet NGVD) off of Bogue Banks, North Carolina (~250 to 2,500 feet offshore) between Beaufort and Bogue Inlets. Areas identified as potential nearshore hardbottom resources, located within the limits of the 25-foot depth of closure, may be impacted as a result of dredging and beach nourishment.
Prior to the field effort, a more detailed sidescan analysis was conducted, and areas of relatively high sonar backscatter were further delineated. In general, coarse bottoms such as shell hash and nearshore ripple scour depressions possess similar sonar reflectance values as hardbottoms. Characteristic sand/shell hash waves were visible in the imagery; however, it was necessary to ground-truth the data to confirm this interpretation. During the period of January 19 to 22, 2009, divers were deployed at these sites to collect samples and video, and, if hardbottom was confirmed, to conduct a benthic ecological characterization. Hardbottom resources were not identified during diver field verification at any sites; sediment samples were collected and catalogued according to the Unified Soil Classification System.
The diver verification and sediment data will satisfy baseline condition needs for the development of the Environmental Impact Statement and Essential Fish Habitat assessment for the Bogue Banks federal storm damage reduction project and will provide the refined nearshore bottom characterization information necessary for USACE to thoroughly assess and rule out potential for hardbottom impact of beach fill equilibration.