Impact of bromide exposure on natural organochlorine loss from coastal wetland soils in the Winyah Bay, South Carolina

Naturally formed halogenated organic compounds are common in terrestrial and marine environments and play an important role in the halogen cycle.

Hurricane Florence Flooding in Georgetown County: A Qualitative Explanation of the Interactions of Estuary and Tidal River

This paper examines data from 18 USGS gauges in the lower Pee Dee Basin in an effort to explain the behavior of the flooding following Hurricane Florence (2018) in Georgetown County, South Carolina. Despite record or near-record flooding in all the tributaries to the Winyah Bay estuary, water levels near the city of Georgetown were well below predicted heights. Floodplain storage in the lower Great Pee Dee, Lynches, and Little Pee Dee River valleys stored over 1.2 million acre-feet of floodwaters, delaying peak stage near Bucksport for five days and reducing peak flow into the Winyah Bay tidal river/estuary system by nearly 50%. An unknown amount of flow from the Winyah Bay tidal river/estuary system flowed through the Atlantic Intracoastal Water Way to Little River rather than through Winyah Bay. The resulting freshwater flow to Winyah Bay only moved the point of tidal stagnation (where upstream tidal flow balances downstream freshwater flow) to near Georgetown. Since the city of Georgetown was near the point of stagnation, water level there was driven by ocean tidal height rather than river flood stage. The lack of discharge data from the tidal rivers in Georgetown County prevents evaluation of the importance of each of these factors and will limit efforts to make quantitative predictions of future flooding in the county.

Response of a Coastal Plume Formed by Tidally Modulated Estuarine Outflow to Light Upwelling-Favorable Wind

This study presents observations of a buoyant plume off Winyah Bay, South Carolina, which was formed under conditions of high freshwater discharge and upwelling-favorable wind forcing. Analysis of observations demonstrates that the response of the anticyclonic bulge formed by tidally modulated estuarine outflow to the light upwelling-favorable wind is more complex than the previously studied far-field response. The latter can be described by a slab-like model with mixing concentrating at the offshore edge of a buoyant layer. The observed plume depth increased from ~3 m near the mouth to 6 m at the offshore edge, with plume depth changing in a steplike fashion rather than continuously. CTD profiles near these steps revealed overturning indicative of vigorous mixing. Estimates of the gradient Richardson number confirmed the likelihood of mixing/entrainment not only at the offshore edge of the plume but also in the proximity of the observed steps. We hypothesize that these steps represent tidal fronts that undergo geostrophic adjustment and are advected offshore by the superimposed Ekman drift. Scaling analysis suggests that mixing and entrainment at the observed interior fronts can be enhanced by superposition of geostrophic and wind-induced shear.