A comparison of the temporal evolution of hydrodynamics and inlet morphology during Tropical Storm Fay (2020)

Abstract

The record-setting North Atlantic hurricane season of 2020 had 30 named storms and reinforced the need for high-resolution, small-scale data collected in the nearshore zone during storm events to characterize storm impacts on coastal settings. To address these needs, hydrodynamic and morphologic data were collected during the 2020 Atlantic hurricane season, capturing fair weather conditions and the passage of Tropical Storm Fay (July 2020) near Chincoteague Inlet, Virginia. A sector-scanning rotary sonar captured high-resolution imagery of bedform evolution and data were analyzed to relate the migration of bedforms to the concomitant hydrodynamic conditions during the storm event. During the peak of the storm on 10 July 2020, significant wave height and period in Chincoteague Inlet were 0.96 m at 9.6 s arriving from the SSW (201°). The ripple field evolved during the storm in a manner consistent with that found in Hay and Mudge (2005): irregular ripples (O 20 cm wavelength) dominated during fair weather conditions, which developed into a washed-out, flat bed state as the storm arrived. During the peak of the storm, lunate megaripples (O 1 m wavelength) formed and migrated shoreward. A substantial outflow of freshwater from Chincoteague Bay occurred for up to seven days post-storm, and sediment transported by this outflow could serve as a yet-unidentified sediment source for the rapid growth of southern Assateague Island. This outflow of freshwater dampened waves and hindered ripple field recovery for up to seven days post-storm. These extreme event datasets are critical to inform coastal flood models and management decisions, as this work recognizes an increased risk of flooding for the town of Chincoteague from even the offshore passage of tropical storms.