Characterization of the evolution of a relocated tidal inlet: Mason inlet, North Carolina

Between January and April 2002, Mason Inlet, situated between Figure Eight Island and Wrightsville Beach, N.C. was artificially relocated 2,800 ft updrift of its most recent position at the southern terminus of a migrating barrier spit. Relocation was chosen from several coastal management options due to increased backbarrier infilling and southerly migration of the inlet that imminently threatened a resort complex and infrastructure on northern Wrightsville Beach. The relocated Mason Inlet provides an ideal site to study the evolution and impacts of a recently relocated system from its inception while simultaneously assessing the relative success of the project. Techniques such as ADCP, RTK GPS, and GIS-based analyses served as tools in the collection of data pertaining to a variety of inlet parameters. Cumulative erosion measured along neighboring shoreline reaches was induced by inlet relocation and subsequent formation of the ebb-tidal delta coupled with channel migration. Key indicators suggest that the system remains flood dominant. Noticeable infilling of the backbarrier persists along with ebb durations exceeding flood durations and flood flow volumes exceeding ebb volumes. JARRETT's (1976) theoretical equation relating tidal prism (TP) and cross-sectional area (AC) appears to be a useful tool for estimation of the relocated Mason Inlet's TP. However, ebb-tidal delta volume after 1.6 years remains well below the equilibrium volume predicted by WALTON and ADAMS' (1976) model. Future modification (e.g. dredging feeder channels) to the system will be needed in order to mitigate the infilling nature of the inlet that historically has led to increased migration to the southwest. Failure to contain the inlet within the proposed “inlet corridor” will result in an unsuccessful relocation effort.