In: Proceedings Coastal Sediments '03. 2003. CD-ROM Published by World Scientific Publishing
Corp. and East Meets West Productions, Corpus Christi, Texas, USA. ISBN 981-238-422-7.
CIRCULATION CHANGE AND EBB SHOAL DEVELOPMENT FOLLOWING
RELOCATION OF MASON INLET, NORTH CAROLINA
Karyn M. Erickson1, Nicholas C. Kraus2, and Erica Eva Carr3
ABSTRACT: In March 2002, under the direction of the first author, a rapidly migrating inlet
located in New Hanover County, North Carolina was relocated. The original entrance to Mason
Inlet was closed, and the inlet was reopened approximately 850 m (2,800 ft) to the north. In
addition, a 1,400-m (4,580 ft) long channel was dredged between the new inlet and the Atlantic
Intracoastal Waterway (AIWW), and a sedimentation basin was constructed west of the new inlet
entrance. Monitoring was initiated to determine if the downdrift beaches receive sediment from
breakup of the abandoned ebb shoal and to assess development of the new ebb shoal, including
natural sand bypassing. This paper examines ebb shoal development, inlet cross-section
equilibration, beach response, and changes in the tidal prism and flow distribution through the
primary two tidal channels connecting the new inlet with the AIWW following the inlet's
relocation. Locational and cross-sectional stability of the entrance channel are also discussed.
During the past 30 years, Mason Inlet has slowly migrated to the south. As a result, the north
shoreline at Wrightsville Beach and the southern beaches at Figure Eight Island have
experienced extensive sand losses and both islands require shore protection to protect their
expansive developments (Fig. 1). Since 1985, the inlet's steady movement to the south has
resulted in the loss of 670 m (2,200 ft) of shoreline at the north end of Wrightsville Beach. In
1997, this migration placed the inlet within 65 ft of the Shell Island Hotel Resort's 10-story north
tower. In addition to the hotel, 38 single-family homes and three condominium developments
were at risk of total loss if the inlet was to continue its southerly migration.
The "imminent threat" to the Shell Island Hotel resulted in the State of North Carolina
granting a variance for a permit to construct a temporary 6 m (20 ft) high, 130 m (425ft) long
geotextile revetment along the hotel's foundation to prevent further movement of the inlet in
1997 (Fig. 2). The State of North Carolina's prohibition of hardened structures is an outcome of
a 1985 general statute that strictly prohibits construction of hardened erosion-control structures
on the ocean shoreline, except for protection of roads and national monuments. This statute
prohibited placement of a terminal training groin or similar structure to control the inlet's
position, thereby requiring the affected property owners to develop a long-term solution without
stabilizing structures. With the impending December 2001 deadline to remove the temporary
revetment approaching, and an agreement by the stakeholder group's property owners to repay
the County for the costs of implementing a long-term solution to the inlet problem, New Hanover
County contracted with a coastal engineering firm to begin work.
1. Erickson Consulting Engineers, Inc., 4319 SW 86 Way, Gainesville, FL 32608.
2. U.S. Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory,
3909 Halls Ferry Road, Vicksburg, MS 39180.
3. Applied Technology & Mgmt., Inc., 2770 NW 43rd St., Suite B, Gainesville, FL 32606.