CHARACTERIZATION OF SEABED DYNAMICS IN THE NEUSE RIVER ESTUARY, NC

Seabed dynamics may impact the chemical and biological conditions in estuaries by releasing pore-water nutrients and altering water column and benthic habitats.  The objective of this study is to characterize the nature of and controls on seabed dynamics in the Neuse River Estuary, NC.  Time-series high resolution radionuclide data from 10 sediment cores (using ⁷Be, ²³⁴Th, ¹³⁷Cs, and ²¹⁰Pb) provided a record of seabed activity and a measurement of sediment erosion and deposition.  Also, time-series river discharge, wind, wave, current, and suspended-sediment-concentration data were obtained to evaluate the physical conditions that led to observed changes in the sediment record.  Sediment transport data were collected with a benthic tripod from August 2005 to September 2006, a period including a category 1 hurricane (Hurricane Ophelia), several nor'easter storms, and a spring river discharge event.  Radionuclide data indicate that ~6 cm of sediment was eroded by Hurricane Ophelia.   During this time, strong wind (>19 m/s) and large waves (>1.5 m H_sig) created elevated bed shear stresses triggering a resuspension event and related erosion.  Data from this time period is used to identify the physical threshold (e.g. wind speed, waves, and bed shear stress) needed to trigger seabed resuspension at this site and insights are used to estimate the frequency of resuspension throughout the year.  During the winter and spring, deposition of 5-8 cm of sediment appears to be related to high river discharge.  Timing, duration, and intensity of coastal storms will play a critical role on their influence in this and other estuarine environments.  It is hoped that this research will provide insights into the mechanisms that link the benthic and pelagic systems.