In order to assess potential dredging and beach nourishment impacts to significant hardbottom resources within and adjacent to the Surf City/North Topsail Beach (SCNTB) Shore Protection Project, USACE required a more refined biological characterization and analysis of flora and fauna species associated with hardbottom resources within the study area. The nearshore study area was located approximately 1100 feet from shore between the -18 to -30 feet NGVD contours from the Surf City/Topsail Beach town border extending through the southern end of North Topsail beach. The offshore study areas are located within 8 offshore borrow sites located approximately 3 to 5 miles offshore in water depths between -30 and -47 feet NGVD.
Previous USACE sidescan and multibeam surveys have identified areas of potentially significant hardbottom within the offshore borrow sites and the nearshore environment. These areas could be impacted as a result of project construction, cross shore beach profile adjustment, or longshore spreading of beach fill. Diver ground-truth investigations of the potential hardbottom sites were therefore required. A more detailed sidescan analysis was conducted prior to the field verification; diver ground-truthing was then conducted to determine absence or presence of hardbottom. For areas where hardbottom was confirmed, a refined biological characterization and analysis of flora and fauna species at representative transect locations were performed.
Characterization and sampling methodology were sufficient to represent a baseline determination of hardbottom habitat conditions. This provided a quantitative and qualitative data set that can be utilized to assess and comparatively evaluate changes in the benthic macro-invertebrate and macro-algal communities at each site throughout future monitoring events.