OFFSHORE SEDIMENT TRANSPORT THROUGH A BLOWOUT AT COQUINA BEACH, OUTERBANKS, NORTH-CAROLINA, USA

Offshore aeolian sediment transport is increasingly recognized as play ing an important role in the sediment budget of beach/dune systems. Th e purpose of this study is to quantify the amount of sediment moved of fshore from the dune crest, through a foredune blowout and across the beach. The study was conducted at Coquina Beach in Cape Hatteras Natio nal Seashore, North Carolina, USA, a location with a shoreline azimuth of 10 degrees. Sediment traps mere deployed in several locations on t he dune, in a blowout, and across the beach on April 19, 1994, January 20, 1995, and February 23, 1995 when the wind direction had azimuths of 230-260 degrees and speeds of 6-15 m s(-1). The highest rates of se diment transport occurred on the unvegetated parts of the blowout rim, at the mouth of the blowout, and on the beach berm. The blowout redir ected sediment transport along the base of the dune north of the blowo ut in a shore parallel direction. Sediment transport was lower at the landward end of the blowout throat and on the back beach between the d une and the berm. Sediment transport diminished noticeably between the berm crest and the swash line because of the moisture content of the beach sediments. The sediment transport patterns suggest that blowouts play an important role in the removal of sediment from a dune system during offshore winds and that they are partially responsible for vari ation in aeolian sediment transport across the beach.