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Title: Engineering Study for Disposal of Dredged Material from Atlantic Ocean Channel on Sandbridge Beach between Back Bay and Dam Neck
Authors: Waterway Survey & Engineering, Ltd.
Keywords: Dredging
Dredging spoil
Beach erosion
Beach nourishment
Sandbridge Beach (Va.)
Publisher: United States. Army. Corps of Engineers. Norfolk District.
Abstract: Deepening of the Atlantic Ocean Channel east of Fort Story and Virginia Beach will produce up to 15 million cubic yards of dredged material. Approximately 4.75 million cubic yards of this dredged material has a D₅₀ size suitable for disposal on beaches, but only ab9ut 3.38 million cubic yards are likely to be available for placement. The Sandbridge shoreline (5.25 miles between Back Bay National Wildlife Refuge and Dam Neck Naval Facility) erodes at an average rate of 6 feet per year, causing the loss of 300,000 cubic yards of sand per year. Sand available from dredging would benefit Sandbridge beach by temporarily slowing this long-term rate of erosion. Sand disposed on Sandbridge beach would also be dispersed along beaches to the north because net longshore transport carries sand northward toward Rudee Inlet at a rate estimated to be slightly over a 100,000 cubic yards per year. This net northward transport would be increased during the 5 years immediately after disposal. If suitable sand from Atlantic Ocean Channel dredging were disposed along 3.6 miles of Sandbridge beach, it will move the shoreline temporarily seaward by 200 feet. After wave-induced redistribution along and across the shore, the long-term shoreline would be 70 feet seaward of the present shoreline, assuming continued beach nourishment of at least 300,000 cubic yards of sand per year. The 3.6 miles of shore recommended for disposal lies between White Cap Land and Marlin Lane; this segment begins about 0.7 miles north of the Sandbridge boundary with Back Bay National Wildlife Refuge (0.25 miles north of the pier) and ends about l mile south of the boundary with Dam Neck Naval Facility. Analysis of sediment samples indicate that sand suitable for disposal should have a minimum median diameter of 0.20 mm. Analysis of bathymetry and coastal exposure, along with the historical record of high erosion rates, suggest that Sandbridge is particularly vulnerable to Atlantic Ocean waves, and that this vulnerability increases towards the south in the study area. A primary reason for this vulnerability is the absence of sand sources external to the Sandbridge shore itself because the southern boundary of Sandbridge is near or at a zone of zero net longshore transport rate.
Description: Technical Report
Rights: Approved for Public Release; Distribution is Unlimited
Size: 114 pages / 5.89 MB
Types of Materials: PDF/A
Appears in Collections:Environmental Documents

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