Physical Sciences and Mathematics Commons^™

Inner-Shelf Circulation And Sediment Dynamics On A Series Of Shoreface-Connected Ridges Offshore Of Fire Island, Ny, John Warner, Jeffrey List, William Schwab, George Voulgaris, Brandy Armstrong, Nicole Marshall

George Voulgaris

Locations along the inner-continental shelf offshore of Fire Island, NY, are characterized by a series of shoreface-connected ridges (SFCRs). These sand ridges have approximate dimensions of 10 km in length, 3 km spacing, and up to ∼8 m ridge to trough relief and are oriented obliquely at approximately 30° clockwise from the coastline. Stability analysis from previous studies explains how sand ridges such as these could be formed and maintained by storm-driven flows directed alongshore with a key maintenance mechanism of offshore deflected flows over ridge crests and onshore in the troughs. We examine these processes both with a limited …

Temporal And Spatial Evolution Of Wave-Induced Ripple Geometry: Regular Versus Irregular Ripples, Timothy Nelson, George Voulgaris

George Voulgaris

Concurrent observations of inner shelf near bed hydrodynamics and acoustic imagery of the seabed are used to relate wave-induced ripple geometry (wavelength and orientation) to near bed directional wave velocities. The observations were collected on the continental shelf of the South Atlantic Bight at water depths of 9.5 and 30 m off the coasts of South Carolina (median size 177 mm) and Georgia (388 mm), respectively. 2-D spectral analysis techniques are performed on the imagery to automate detection of ripple wavelength, orientation, and irregularity. Our analysis shows that ripple irregularity is a time-dependent process dependent on magnitude, direction, and duration …

Sediment Resuspension, Flocculation And Settling In A Macrotidal Estuary, Ya Ping Wang, George Voulgaris, Yan Li, Yang Yang, Jianhua Gao, Jia Chen, Shu Gao

George Voulgaris

Estuarine boundary layer and water column in situ measurements of hydrodynamics, sediment resuspension and sediment particle size distribution are presented for a macrotidal environment in SE China. Vertical and tidal variability of sediment size and its relation to turbulence and hydrodynamic forcing are examined using time-series from two week long experiments after they are phase averaged to reconstruct typical neap and spring tidal cycles. In situ particle size distributions obtained using laser diffraction show clear evidence of flocculation processes that change dynamically during the tidal cycle. Mean particle size of particles in suspension is found to be one order of …

Predicting Wave-Induced Ripple Equilibrium Geometry, Timothy R. Nelson, George Voulgaris, Peter Traykovski

George Voulgaris

A comprehensive database of existing (since 1954) field and laboratory measurements of ripple geometry is compiled and combined with newly collected field data to examine the performance of ripple equilibrium predictors. Re-analysis of this enlarged ripple geometry data set reveals that ripples formed from monochromatic waves scale differently than ripples formed from random waves for many existing ripple predictors. Our analysis indicates that ripple wavelengths from the two data sets collapse into a single scaling when the semi-orbital excursion and sediment grain diameter are used as normalizing factors. Ripple steepness remains relatively constant for both regular and irregular wave conditions …

Holocene Sediment Distribution On The Inner Continental Shelf Of Northeastern South Carolina: Implications For The Regional Sediment Budget And Long-Term Shoreline Response, Jenny Denny, William Schwab, Wayne Baldwain, Walter Barnhadt, Paul Gayes, Robert Morton, John Warner, Neil Driscoll, George Voulgaris

George Voulgaris

High-resolution geophysical and sediment sampling surveys were conducted offshore of the Grand Strand, South Carolina to define the shallow geologic framework of the inner shelf. Results are used to identify and map Holocene sediment deposits, infer sediment transport pathways, and discuss implications for the regional coastal sediment budget.

The thickest deposits of Holocene sediment observed on the inner shelf form shoal complexes composed of moderately sorted fine sand, which are primarily located offshore of modern tidal inlets. These shoal deposits contain ∼67 M m3 of sediment, approximately 96% of Holocene sediment stored on the inner shelf. Due to the lack …

Storm-Induced Inner-Continental Shelf Circulation And Sediment Transport: Long Bay, South Carolina, John Warner, Charlene Silvester, Brandy Armstrong, George Voulgaris, Timothy Nelson, William Schwab, Jane Denny

George Voulgaris

Long Bay is a sediment-starved, arcuate embayment located along the US East Coast connecting both South and North Carolina. In this region the rates and pathways of sediment transport are important because they determine the availability of sediments for beach nourishment, seafloor habitat, and navigation. The impact of storms on sediment transport magnitude and direction were investigated during the period October 2003–April 2004 using bottom mounted flow meters, acoustic backscatter sensors and rotary sonars deployed at eight sites offshore of Myrtle Beach, SC, to measure currents, water levels, surface waves, salinity, temperature, suspended sediment concentrations, and bedform morphology. Measurements identify …

Exploring The Persistence Of Sorted Bedforms On The Inner-Shelf Of Wrightsville Beach, North Carolina, Benjamin Gutierez, George Voulgaris, Robert Thieler

George Voulgaris

Geological studies offshore of Wrightsville Beach, North Carolina reveal subtle large-scale regions of coarse sand with gravel and shell hash (widths between 100 and 200 m and negative relief of ∼1 m) that trend obliquely to the coast. It was previously suggested that these regions serve as conduits for sand exchange between the shoreface and inner shelf during storm-associated downwelling. Consequently they were classified as rippled scour depressions. More recently, the role of alongshore flows and self-organization as a result of inhibited settling of fine sand has been discussed. In this study, 45 days of near-bed current measurements were analyzed …

The In Situ Passive Acoustic Measurement Of Shingle Movement Under Waves And Currents: Instrument (Tosca) Development And Preliminary Results, George Voulgaris, Michael Wilkin, Michael Collins

George Voulgaris

An instrumented platform (TOSCA) is described for monitoring coarse-grained sediment transport in high (wave and tidal) energy environments. The system consists of a number of sensors which measure: instantaneous current velocities at three levels; sea surface elevation; and self-generated noise (SGN) caused by intercollision of particles in transit. SGN is related to transport rates, on the basis of laboratory calibration; this, in turn, allows a correlation with simultaneous near-bed shear stress to be established. During the field measurements, PC-based real-time data transmission is realised through the use of a (buoyed) radio telemetry system.

TOSCA has been deployed in eastern Christchurch …