The Effect of Regional Winds on Subtidal Along‐Inlet Currents at Oregon Inlet, NC

Abstract

AbstractWind influence on tidal inlet hydrodynamics is examined using 40 days of wind, water level, and current observations collected in Spring 2019 at Oregon Inlet, NC, a large (1 km wide, 1–13 m deep) meso‐tidal inlet with complex delta systems. Wind velocities through the inlet (ranging 0–18 m/s) are modulated at subtidal timescales and are well correlated (R = 0.87) to a subtidal component of the water level slope through the inlet. The subtidal wind and water level slope are also well correlated to the subtidal current along the principal flow axis in the main inlet channel (R = 0.92 and 0.96, respectively). In combination with findings from previous studies, these findings suggest that regional winds induce the subtidal water level slope through the inlet by causing opposing setup/setdown to either side of the inlet. A force balance at the inlet demonstrates that the wind‐induced pressure gradient forces the subtidal currents, with wave forcing and local wind shear acting as lower‐order influences. The magnitude of the subtidal current is substantial, exceeding that of the tidal currents 45% of the time. Cumulatively, these findings indicate that regional winds exert a first‐order control on the currents at Oregon Inlet and cause irregular hydrodynamic patterns not well described by the traditional inlet classification scheme. Regional geographic characteristics may contribute to the high level of wind influence at Oregon Inlet, but similar processes are likely to be important to net flow dynamics at other inlets with large, shallow inland water bodies.