Fig. 2. Mason Inlet (Dec 2001) prior to construction of inlet relocation project.
Both the Town of Wrightsville Beach and Figure Eight Island have undertaken inlet
maintenance dredging for navigation and to provide material for beach nourishment. Due to
extensive layers of rock along the North Carolina coast, very limited offshore sand sources are
available and thus, nourishment projects commonly depend on inlet maintenance material as a
sand source. Masonboro Inlet, at the southern end of Wrightsville Beach, is a federally
maintained inlet that provides more than 460,000 m3 (600,000 yd3) of material to nourish
Wrightsville Beach every 3 years. Similarly, at Figure Eight Island, the purpose of the dredging
at Banks Channel and Rich Inlet has been to maintain navigation and to provide a source of sand
for protection of the island's beaches. According to a study by Cleary (May, 1990), the southern
shoreline of Figure Eight Island experienced a recession rate of 4.1 m/yr (13.6 ft/yr) between
1984 and 1989. Since 1990, the beaches immediately updrift of Mason Inlet have continued to
experience chronic, high rates of erosion. As is typical of rapidly migrating or unstable inlet,
Mason Inlet is absent a well-developed, ebb tidal shoal and experiences a strong downdrift
movement of sand onto the inlet's updrift depositional planform, resulting in chronic erosion of
the updrift beaches. For this reason, a goal in formulating a long-term solution to the migration
of Mason Inlet was to address this chronic erosion problem. The native sand mean grain sizes at
these beaches range from 0.22 to 0.25 mm, whereas channel maintenance material is typically
finer, characterized by mean grain sizes of 0.18 to 0.22 mm.
The purpose of this paper is to review the project's history and the first year of observations
of morphology and hydrodynamics following relocation of the Mason Inlet channel. Data are
presented to examine 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.