The Study of the Hurricane-Induced Storm Surge and Bay-Ocean Exchange Using a Nesting Model

Abstract

Lagoon systems are more heavily impacted by hurricanes, whereas the relevant storm surge modeling studies have been paid little attention to lagoon systems and the storm-induced exchange in lagoon systems is even less understood. To address this gap, a three-dimensional unstructured grid-based model was configured for the Maryland Coastal Bays, a typical lagoon system with two unique inlets (Ocean City Inlet (OCI) and Chincoteague Inlet (CI)), to investigate how Hurricane Sandy impacted inlet dynamics. A nesting model framework was applied to provide the necessary remote forcing from a large model domain and maintain the intricate shoreline and bathymetry of an inner model domain. Results indicated that the flux patterns varied in response to the change in wind direction and rising/falling high water levels from the coastal ocean, rather than a single flow pattern during the passage of Sandy. From October 29 05:00 to 17:00 UTC, mild (> 10 m/s) and strong (> 15 m/s) northerly winds accompanied by the rising high water level from the coastal ocean promoted a mean inflow pattern at the OCI and a mean outflow pattern at the CI. Strong southwesterly winds (> 15 m/s) dominated in the bays from October 30 03:00 to 15:00 UTC. Under strong southwesterly winds and falling high water levels from the coastal ocean, flux was transported landward at the CI and seaward at the OCI. Sensitivity experiments on various storm temporal scales showed that a net inflow pattern occurred in the bays, and the net exchange amounts became smaller in response to longer storm durations. Residual effect of relatively high river flow from Sandy could still influence the salinity at the OCI, whereas the CI salinity was not affected by river flow owing to a long distance between the CI and river locations.