HOW EFFICIENT IS MOTHER NATURE AT OREGON INLET,NORTH CAROLINA?

摘要

The stability and processes at Oregon Inlet, located on the Outer Banks ofrnNorth Carolina, have direct implications for the local community and surroundingrnshoreline. With one of the highest wave climates on the East Coast, longshore energyrnflux mobilizes large amounts of sediment, which if not bypassed can cause erosionrndowndrift. Budgeting considerations for the increasing expenses associated with thernrequired annual dredging have dictated a need to understand the bypassing efficiency atrnthe inlet. Using historic aerial photography and recent survey data collected by the USrnArmy Corps of Engineers’ Field Research Facility, various depositional “sinks” havernbeen identified and monitored to examine their storage potential in an effort to determine:rn1) how much sand bypasses or moves into the inlet, and 2) the effect of bypassingrnefficiency on the surrounding coastline. A direct link between the gross potentialrnsediment transport and the natural bypassing efficiency was found. Data for 1989-2001rnshow that during energetic years, up to 71 percent of the sediment was bypassed, whilernduring years of lower wave energy the bypassing was as low as 19 percent. The ebbshoalrncomplex of this 156-year-old inlet was found to be at equilibrium volume and itrnserves as the primary sediment pathway. Removal of sediment by dredging, depositionrnon the flood shoal, and spit evolution were identified as important sinks for sediment.rnSignatures of bypassing inefficiency were observed as shoreline erosion on the downdriftrnsides, usually to the south, but at times to the north.