Abstract: Onshore Sediment Transport--Profile Study of Dredge Disposal in Littoral Zone, New River Inlet, North Carolina

R. K. Schwartz, F. R. Musialowski

New dredge-disposal techniques may serve the dual role of aiding sand bypassing across coastal inlets and beach nourishment, providing that dredged sediments placed seaward of the surf zone move shoreward into that zone.

During the summer of 1976, 26,750 cu m of coarse sediment was dredged from New River Inlet, barged downcoast, and placed in a 240-m coastal reach between the 2- and 4-m depth contours. An 8-week study was conducted to examine bathymetric changes on the disposal piles and in the adjacent beach-nearshore area.

The sediment piles created a local shoal zone with minimum depths of 0.6 m. Wave shoaling and breaking caused rapid erosion of pile tops and a gradual coalescing of piles to form a bar seaward (~90 m) of a surf-zone bar. The disposal bar eventually migrated landward at an average rate of 1.8 m/day. With development of the disposal bar, the inner surf-zone bar eroded or was displaced landward, and the adjacent trough began to fill. In general, final surveys showed only slight accretion at the base of the foreshore, almost complete filling of the trough, and a platform or new trough at the initial surf-zone bar position. The disposal bar created a more seaward surf-zone boundary, although in some cases was eroded entirely. Profiles adjacent to the disposal area showed negligible accreti n seaward of the surf-zone bar, but similar trough filling. Dispersal of the coarse disposal sediment is interpreted to have been primarily landward into the surf zone, then longshore.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC