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Contact UsSite IndexSearchDepartment HomepageAllen E. Paulson College of Science and Technology
Department of Geology and Geography
10 Ocean Science Circle, Skidaway Island, Savannah, Georgia 31411
Fax: 912-598-2366
Dr. Clark Alexander
clark@skio.peachnet.edu
Professor of Geology, Director of the Applied Coastal Research
Laboratory
Education:
Ph.D. North Carolina State University, Marine Sedimentology
M.S. North Carolina State University, Marine Geology
B.S. Humboldt State University, Oceanography (Cum Laude)
B.A. Humboldt State University, Geology
Current Activities:
Dr. Alexander has focused on research both locally and nationally
in the area of sedimentary processes and their products in coastal
and continental margin environments. He continues to work in Northern
California on the STRATAFORM program, which seeks to understand
the signatures of geologic events (floods, storms, earthquakes
and massflows) in the stratigraphic record. A project in Santa
Monica Bay in Southern California, which is examining the historical
record of pollutant input to the Bay and the processes of sediment
redistribution on the continental margin, is in its final stages.
Another historical pollution study, this one sited in Delaware
Bay, has recently been funded. He has been working with GSU faculty
members Henry and Foyle to examine the processes of sediment transport
and erosion on the Savannah River ebb-tidal delta, and on determining
the integrity of the Miocene aquiclude overlying the Floridan
aquifer, our major source of drinking water in the GA/SC coastal
region. Alexander has also been continuing his monitoring of a
wetlands remediation site on the Ogeechee River, where the GA-DOT
is remediating an old rice impoundment to mitigate wetlands destruction
during road building. Because of the great interest in our natural
environment, he continues to give about a dozen talks annually
to civic and school groups on oceanography, barrier island geology,
and earthquakes in the Southeast. He also continues to be involved
with local and statewide environmental issues by participating
in the Stakeholder Evaluation Group for the Savannah Harbor deepening
as well as in the Aquifer Subcommittee and by serving on the Georgia
State Shore and Marshlands Protection Committee.
To read more about Dr. Alexander click here
Dr. Vernon J. Henry
Retired in 2003.
henry@skio.peachnet.edu
(912) 598-2463
Education:
B.S. in Geology, Lamar State College of Technology, Beaumont,
Texas
M.S. in Oceanography, Texas A & M College
Ph.D. in Oceanography, Texas A & M College, College Station,
Texas
Current Activities - Dr. Henry is interested in studying
coastal and shelf processes and features; mapping coastal
and marine bottom and subbottom geologic features using high resolution
seismic and sonar systems; geologic development of barrier
islands and associated environments; and history and monitoring
of changes in shorelines and saltwater wetlands
Facilities
Extensive archive collection of cores and peels from the Georgia
Bight
Applied Acoustic Engineering towed acoustic source used for
collecting high-resolution, single channel, seismic reflection
data on the Georgia shelf.
UNOLS Research Vessel Blue Fin, operated by the Skidaway Institute
of Oceanography and the platform used for much of the coastal
and shelf work being conducted at ACRL.
EPC 1086 (TM) Thermal Printer used in conjunction with ISIS
DelphWin Seismic (TM) for real-time subbottom data plotting.
ISIS / Triton Elics (TM) system used for collection, processing,
and display of digital sidescan and subbottom geophysical imagery.
Environmental
Topics of Interest
by Tony Foyle (now a Faculty Member at Behrend College, Erie, PA)
Have you ever wondered about that clear
cool liquid that comes from our faucets? Yes, we're talking about
groundwater! Not everyone realizes that groundwater use in coastal
Georgia is of major significance not only to our state, but also
to our neighbors in South Carolina and northern Florida. Because
Georgia's 24 coastal counties are expected to experience a continued
increase in population over the next several decades, our groundwater
is a fundamental issue for our legislators to consider when planning
to balance sustainable economic development with protection of
environmental resources in southeastern Georgia. In a nutshell,
the availability of sustainable long-term supplies of groundwater
will be of critical importance for our future.
In coastal Georgia, studies by the U.S.
Geological Survey show that we use most of our groundwater for
public water supply and industrial needs. Most of that water is
supplied from a single aquifer (a layer of rock or sediment that
can supply economically significant quantities of water ) known
as the Floridan Aquifer System. This aquifer extends from South
Carolina, through Georgia, and into Florida and Alabama; it is
present beneath both the coastal plain upon which we live and
the continental shelf above which we fish and sail. Because of
its geographic extent, the management of water in the aquifer
is, and will continue to be, an inter-state issue as usage practices
in one state can affect the availability and quality of water
in an adjacent state. About 90% of the groundwater withdrawn from
the Floridan Aquifer System in coastal Georgia is actually taken
from its uppermost part which is known as the upper Floridan aquifer
(UFA). The UFA is a pale-colored limestone that originally accumulated
in warm subtropical to tropical seas more than 25 million years
ago (for reference, the dinosaurs became extinct about 65 million
years ago). It has since been periodically eroded and weathered
during times of lowered sea level and buried by younger sediments
during times of higher sea level. In our area, the UFA lies anywhere
from 19 to 200 ft below sea level and ranges from 50 to 200 ft
in thickness. If we were to somehow drop sea level by a couple
of hundred feet (an event that would need the help of an ice age!)
and peel off the overlying sediments that we now live upon, the
top surface of the aquifer would resemble karst limestone landscapes
we see in western Europe today.
Massively bedded limestones and karst topography in the Burren,
western Ireland
Every day in coastal Georgia the pores, cracks, crevices, and
subterranean caverns in the UFA provide approximately 350 million
gallons of crystal-clear potable water for our use, a volume that
has been steadily increasing ever since water was first pumped
from the aquifer at Savannah about 115 years ago. To put 350 million
gallons per day in perspective, that's equivalent to a column
of water about 800 feet high with a base (footprint) the size
of a football field. Recent data from the U.S. Geological Survey
show that Chatham County alone consumes about 76 million gallons
of Floridan water daily (equivalent to a similar column of water
about 175 feet high).
Throughout the latter half of the 20th
century, large volumes of groundwater have been pumped out of
the UFA in the Savannah - Hilton Head region; as a result of this,
the aquifer's potentiometric surface (which you can think of as
an imaginary water table within the aquifer) is now over 120 feet
lower in elevation at Savannah than it was in the late 19th century.
What this means is that wells which would have flowed freely at
the land surface (i.e., artesian wells) in Liberty, Bryan, and
Chatham counties (Georgia); and Jasper and Beaufort counties (South
Carolina) in the late 1800s now have to be pumped as the water
pressure in the aquifer is no longer sufficient to move water
up and out of the well bore. Prior to the 1800s, early Spanish
explorers were even able to obtain fresh water from seafloor seeps
offshore. When viewed on a map today, the depressed potentiometric
surface forms a cone of depression (an upside-down cone) that
has a radius of up to 30 miles, is centered on Savannah, and underlies
eight coastal counties. The cone of depression developed, and
continues to persist, because the pumped water cannot be replaced
quickly enough through natural inflow from other parts of the
aquifer; the inverted apex of the cone now lies about 100 feet
below sea level.
Recent potentiometric map for the upper
Floridan aquifer showing the cone of depression centered on Savannah.
As you might expect, when fresh groundwater is pumped from our coastal aquifer, there is the potential for sea water, and not just fresh water, to move into the aquifer and towards the pumping sites to replace the water being withdrawn. Certain conditions allow this problematic "seawater intrusion" effect to occur. The two primary conditions are (1) the local absence of a "cap rock" or aquiclude, which is a layer of rock or sediment that would restrict the flow of sea water downward through the seabed and into the underlying aquifer, and (2) a negative pressure gradient (as we would find within the Savannah - Hilton Head cone of depression) between the ocean and the aquifer which would induce sea water to move downward into the aquifer. Both of these conditions occur, unfortunately for us, in the Georgia - South Carolina coastal area.
To address this environmental concern,
the Georgia Environmental Protection Division (EPD) is currently
funding a two-year project at Georgia Southern University's Applied
Coastal Research Lab (Jim Henry and Tony Foyle) and the Skidaway
Institute (Clark Alexander) to identify areas in coastal Georgia
and South Carolina where seawater has the potential to leak into
the UFA. Several other academic, municipal, state, and federal
entities are also being funded to tackle different aspects of
EPD's Interim Strategy (1997-2005) for managing saltwater intrusion
in the UFA of southeastern Georgia. Our collective results will
form the scientific basis upon which EPD can formulate and adopt
a comprehensive groundwater-management strategy.
Shift change on the US Army Corps of Engineers Drilling Barge
"Explorer"
We use marine geophysical survey and drilling
data to identify coastal areas where (1) the Miocene aquiclude
overlying the UFA may be breached, thin, or missing, and (2) where
the overlying water column is saline. In areas where these two
conditions are met, particularly within the Savannah - Hilton
Head cone of depression, there will be a strong likelihood that
seawater is getting into the aquifer and is heading towards our
pumping wells.
General stratigraphic scenarios for seawater
intrusion into the upper Floridan aquifer
In coastal Georgia and South Carolina,
the Miocene aquiclude consists mostly of sands, silts, and clays
that were deposited about 5 to 25 million years ago. The aquiclude
can be as much as 160 ft thick, but in localized areas it can
be thin or absent as a result of two natural processes. Firstly,
in many coastal creeks today, tidal currents are of sufficient
strength to erode the channel bottoms and cut into or through
the aquiclude and expose the UFA to seawater. Some of these tidal-scour
holes are as much as 70 feet deep, a depth you wouldn't ordinarily
find on the Georgia coast unless you were at least 25 miles offshore.
These tidal-scour holes are potential trouble spots, especially
in Beaufort County where the aquifer is shallow. Secondly, several
times over the past 2 million years, sea level was as much as
300 ft lower than it is today. During these times of lowered sea
level, the most recent of which occurred about 18,000 years ago,
the Savannah River flowed across the exposed continental shelf
to its paleo-mouth located 60 to 80 miles seaward of where it
is today. At certain points along its route, the river channel
cut down into, and locally through, the aquiclude. While the paleochannels
have since been filled with sands and gravels, these younger (and
generally coarser) sediments are not as efficient an aquiclude
as the Miocene strata. These paleochannels are also potential
trouble spots, especially seaward of Hilton Head Island where
the aquifer is relatively shallow.
Dip-oriented digitized seismic section
offshore of Hilton Head Island showing incision of the aquiclude
by a Quaternary paleochannel of the Savannah River system.
Our initial data has allowed us to identify several areas of concern where the UFA is shallow enough, the Miocene aquiclude thin enough, and the UFA's potentiometric surface depressed enough for there to be a significant risk of seawater intrusion into the UFA. The next step for our group of Interim Strategy participants is for Georgia, South Carolina, and the U.S. Geological Survey to use our information to determine the locations of planned monitoring/detection wells in coastal Georgia and South Carolina. That data, in turn, will be incorporated into modeling efforts and scenario development. Approximately five years from now, our increased understanding of this coastal aquifer will form the sound scientific basis upon which coastal Georgia's future groundwater management plans can be constructed.
COASTAL CHANGE IN GEORGIA: STATE OF KNOWLEDGE AND GEO-RESEARCH NEEDS
By Tony Foyle (Faculty Member at Behrend College, Eire, PA)
MORPHODYNAMICS AND HYDRODYNAMICS OF THE GEORGIA COAST
The Georgia Bight extends for a distance
of approximately 1200 km between Cape Hatteras, North Carolina,
and Cape Canaveral, Florida. At its apex, the Georgia coast is
a classic mesotidal barrier coast that falls within the mixed
energy / tide-dominated field (Hayes 1979, 1994; Davis and Hayes,
1984). Spring tidal ranges are 2 to 3 m, the second highest on
the US east coast, and are the dominant hydrodynamic forcing agent;
mean wave height ranges from only 0.6 to 1.0 m (Hayes and Sexton,
1989). Dominant winds are typically produced by extratropical
cyclones while hurricane events are less significant compared
to the flanks of the Georgia Bight in Florida and North Carolina.
Map of the Georgia coast with barrier islands (click on thumbprint)
In the early Pleistocene, the Georgia
coast was a wave-dominated system similar to that of North Carolina
today (Rhea, 1986). Large cuspate deltaic headlands were developed
at the paleo-mouths of the Savannah and Altamaha Rivers, while
large strandplain systems similar to those at Nayarit (Mexico)
and the Doce River (Brazil) characterized the coast. Today, the
Georgia coast is tide-dominated and is characterized by eleven
relatively short drumstick barrier islands that are separated
by large estuaries and backed by expansive salt marshes. Four
of the barriers are developed (Tybee, Sea, St. Simons, and Jekyll
Islands) and are experiencing growing developmental pressures;
the remaining seven islands are in relatively pristine states
with minimal development and little coastal infrastructure at
risk from erosion. Georgia's barrier islands average about 8 km
in length which contrasts markedly with those further to the north
and south on the Georgia Bight which attain average lengths of
as much as 38 km (Brown, 1977; Hayes, 1994). Large tidal prisms
favor relatively stable inlets between barriers, with ebb-dominated
flow fields and well-developed ebb tidal deltas. Additionally,
extensive marsh development behind the islands and well-developed
back-barrier drainage networks tend to enhance inlet stability.
At large time and space scales, longshore sediment transport is
predominantly southward in response to the highest wave-energy
events being associated with northeasterly winds; however, local
reversals do occur seasonally (due to different summer and winter
wave regimes) and spatially (such as in coastal areas immediately
downdrift of ebb tidal deltas).
Click on these two thumbprints to see views of Tybee Island, GA
As part of the long-term Holocene rise in sea level, barrier islands on the Georgia coast are moving landward with sand being supplied from cannibalistic shoreface retreat (Swift et al., 1991) and from fluvial and tidal-channel reworking of Pleistocene deposits on the back sides of the barrier coast. Today, more than 70% of the available Holocene sand in the coastal system is stored in well developed ebb tidal deltas which act as temporary sediment sources and sinks (Hayes, 1994). Little new sediment is being supplied to the coastal system either by Piedmont-draining rivers (such as the Altamaha and Savannah) or Coastal Plain rivers (such as the Satilla and Ogeechee). This is due to anthropogenic effects (such as river damming, dredging, increased stream-bank vegetation) and natural processes (primarily fluvial base level adjustments to the Holocene rise in sea level).
At human time scales, coastal response to the ongoing Holocene transgression is significantly more variable as processes such as tidal-channel switching, swash bar welding, navigation enhancements, coastal engineering, and storm events exert control on the supply and sink of littoral sediments. The interaction of the retreating shoreface with older (antecedent) stratigraphy also influences the distribution of erosional and accretional zones, and the concomitant direction of shoreline change, as new sources of littoral sand are intersected by shoreface hydrodynamic forces. Variation in the along-coast occurrence of paleo-sand deposits (primarily paleo-inlet and paleo-barrier sequences) will affect the direction and rate of shoreline change because of spatial variability in sediment supply to the littoral system. At the same time, however, variations in the rates and directions of shoreline change are also strongly controlled by variations in the wave and tidal energy flux, which in turn influence sediment flux along the coast.
WHY IS COASTAL RESEARCH IMPORTANT?
A recent report by the H. John Heinz III Center for Science, Economics and the Environment states that, for the US coast as a whole, approximately 1500 homes will be lost to erosion each year for the next several decades at an annual cost to coastal landowners of approximately $530 million (Heinz Center, 2000). Several recent National Science Foundation (NSF), US Geological Survey (USGS), and National Research Council (NRC) documents on future research priorities in the arena of coastal geology recognize that there is a critical need for high-resolution integrated research in the coastal zone, specifically on coastal change processes (FUMAGES, 1996; NRC, 1990; NSF, 1999; NSF-EAR, 1999; Fletcher et al., 2000; NSF 2000; USGS, 2000). These documents, developed by leading US and international research geoscientists, highlight the fact that a thorough understanding of sedimentary processes, morphodynamical substrate evolution, and coastal stratigraphic frameworks is required to better understand complex, non-linear, coastal systems and to develop effective process-response models. Once this level of scientific understanding is achieved, coastal zone management (and coastal hazard mitigation specifically) can move from reactive and crisis-management decision making toward a more proactive stance that will reduce the economic and human losses that are associated with increasing development of the dynamic US coastal zone.
Georgia's coast is an ideal "field laboratory" within which to study coastal evolution in a tide-dominated setting, both under natural conditions and under conditions of limited coastal engineering and/or renourishment. Georgia's four developed barrier islands (Tybee, Sea, St. Simons, and Jekyll Islands) are prime candidates for coastal change and shallow stratigraphic investigations of partly engineered/renourished systems. Georgia's seven other islands are either state, federal, or non-profit foundation-owned islands and are not as critically in need of baseline data due to the lack of infrastructure at risk from coastal erosion. However, these undeveloped islands do serve as models for contrasting the coastal response of undeveloped systems with those of developed or partly engineered systems within the same hydrodynamic regime (i.e., on the apex of the Georgia Bight).
WHAT IS THE CURRENT STATE OF KNOWLEDGE FOR THE GEORGIA COAST?
The Georgia coast is the last great unmapped area on the Atlantic coast in terms of the acquisition of shoreline-change data for coastal management and hazard mitigation purposes. Shallow stratigraphic framework studies of the Georgia barrier system were at a peak in the 1970s and early 1980s but significantly less work has been conducted during the late 1980s and 1990s (Taylor et al., 1995). While Georgia only recently (1998) adopted its Coastal Management Program under NOAA's National Coastal Zone Management Program (OCRM, 1999), as yet there is neither an effort in place to obtain baseline data on the state of the shoreline nor an effort to regularly map the shoreline. Nationally, obtaining this type of fundamental scientific information is very important for future coastal management and hazard mitigation planning (NRC, 1990). This information is all the more important for Georgia considering that the South Atlantic states collectively could lose as much as 1000 square miles of coastal lands over the next 100 years (NOAA, 1999). Unlike most other states participating in the NOAA coastal management program, Georgia does not have good up-to-date information on average annual erosion rates which are an important input for determining setback lines for (sustainable) coastal development.
The most up-to-date published information on coastal change in Georgia is contained in Nash (1977) and Griffin and Henry (1982). While highly accurate given the methods and equipment used at the time, by today's standards both studies have limitations in terms of being able to quantify coastal change to the degree of accuracy that is possible and generally required since the advent of modern GIS and shoreline-mapping systems (Anders and Byrnes, 1991; Crowell et al., 1991; Danforth and Thieler, 1992; Thieler and Danforth, 1994a,b). Other works on the Georgia coast are generally focused on individual developed islands and inlets, generally in connection with beach nourishment, coastal engineering, or navigation-channel dredging projects (Pilkey and Richter, 1965; Oertel, 1975; Howard and Frey 1980; Henry et al., 1987; Frey and Howard, 1988). Most recently, FEMA-sponsored coastal hazard assessments have been conducted in Glynn County on the central Georgia coast (Heinz Center, 2000).
WHO BENEFITS FROM COASTAL CHANGE RESEARCH?
COASTAL RESEARCHERS
An understanding of sedimentary processes, morphodynamical substrate
evolution, and coastal stratigraphic frameworks is required by
coastal scientists to better understand complex, non-linear, coastal
systems and to develop effective process-response models. Once
this level of scientific understanding and predictive capability
is achieved, predictive models of future coastal change can ultimately
be used to help reduce the economic and human losses that accompany
development of the dynamic US coastal zone.
Manipulating shoreline data to obtain statistically valid information on the directions and rates of long- and short-term shoreline change, for example, would be a major step in filling an existing knowledge void (in terms of availability, completeness, and currency) for the Georgia coast. Similarly, determining upper shoreface and barrier system stratigraphic frameworks would reveal the role exerted by shallow stratigraphic and surficial sedimentary frameworks on the erosion, dispersal, and deposition of sediment on the upper shoreface and barrier system, as well as on variability in shoreline change vectors. Future studies would then be able to build upon this morphodynamic / stratigraphic framework by focusing on hydrodynamic processes to produce a cross-disciplinary and integrated understanding of the process-response characteristics of the coastal system. This latter work would require meteorologic and physical oceanographic research components in order to quantify the wind, wave, and tidal forces that cause sediment movement on the upper shoreface. An added benefit for researchers is that an understanding of the processes controlling coastal change in Georgia would be somewhat transferable to similar mesotidal systems both nationally and internationally. Coastal geologic research forms a valuable component in the wealth of cross-disciplinary knowledge that coastal scientists are currently assembling to understand coastal change and its influence on living systems.
COASTAL MANAGERS
Good coastal-change information generally paves the way for coastal
hazard management strategies to evolve from reactive and crisis-management
decision making toward proactive decision making. The Georgia
Coastal Management Program would, for example, stand to gain significantly
from coastal research because a centralized source of coastal
geoscience data is not currently available to Georgia's coastal
managers. Since Georgia has only recently spun up its own NOAA-sponsored
coastal management program, this type of information is doubly
important in helping the state get up to speed in developing databases
comparable to other coastal states. Dissemination of research-derived
information in a format and content usable to coastal managers
would provide the Georgia Program with a sound knowledge of the
rates, magnitudes, directions, and factors controlling coastal
change in Georgia. Information on Georgia's coastal vulnerability,
similar to that generated by the USGS as part of a national assessment
of coastal vulnerability (Thieler and Hammar-Klose, 1999), would
also be very useful to Georgia. Similarly, results from shoreface
and shallow framework studies would provide relevant information
on, for example, the fate of beach nourishment. The fundamental
scientific knowledge generated through coastal geoscience research
forms an integral input to the decision making process in coastal
zone management and planning as the Georgia coast continues to
experience developmental pressures in the early 21st century.
THE GENERAL PUBLIC, EDUCATORS, AND STUDENTS
It has been recommended at the national level (NRC, 1999), and
is now being adopted as policy (USGS, 2000), that geoscience research
by organizations such as the USGS be conducted within the framework
of societal relevance (applied geologic research) and not just
as research for the sake of research. Results should ideally be
available at a level of understanding that is geared to the different
audiences that need, or stand to gain the most from, that information.
The general public are the ultimate end users and beneficiaries
of coastal geoscience research being recommended, formulated,
and conducted at the national level within the framework of earth
systems science. This is because coast-related policies that incorporate
the research results become implemented at the state and community
level where the public are directly affected and can have input.
Educators play a role in the process by passing new (geo)scientific
knowledge on to students who ultimately become members of the
general public. A general public better informed on coastal-related
issues is a general public better able to make informed decisions
on promulgating sustainable economic development of the dynamic
coastal zone.
BIBLIOGRAPHY
Anders, F.J., and Byrnes, M.R., 1991.
Accuracy of shoreline change rates as determined from maps and
aerial photographs. Shore and Beach 59(1), 17-26.
Brown, P.J., 1977. Variations in South Carolina coastal morphology.
Southeastern Geology 18, 259-264.
Crowell, M., Leatherman, S. P., and Buckley, M. K., 1991. Historical
shoreline change: Error analysis and mapping accuracy. Journal
of Coastal Research 7(3), 839-852.
Danforth, W. W., and Thieler, E. R., 1992. Digital Shoreline Analysis
System (DSAS) User's Guide, Version 1.0. Reston, Virginia. US
Geological Survey Open-File Report No. 92-355, 42 p.
Davis, R.A. and Hayes, M.O., 1984. What is a wave-dominated coast?
Marine Geology 60, 313-329.
Fletcher et al. (12 others), 2000. Research in the sedimentary
geology of the coastal zone and inner shelf Report of NSF-sponsored
workshop, Honolulu, Hawaii, November 1999. GSA Today 10(6), 10-11.
Frey R.W. and Howard, J.D., 1988. Beach and beach-related facies,
Holocene barrier islands of Georgia. Geology 125, 621-640.
FUMAGES, 1996. NSF Workshop on the Future of Marine Geology and
Geophysics. Chapter 4 - Dynamics on the shelf and shoreface and
its imprint on the seafloor and sediment column. Website at http://www.joi-odp.org/FUMAGES/FUMAGES.html
Griffin, M.M., and Henry, V.J., 1984. Historical changes in the
mean high water shoreline of Georgia, 1857-1982. Georgia Department
of Natural Resources Bulletin 98, 96 p.
Hayes, M.O., 1979. Barrier island morphology as a function of
tidal and wave regime. In: S. Leatherman (Editor), Barrier
islands from the Gulf of St. Lawrence to the Gulf of Mexico. Academic
Press, New York, pp. 1-27.
Hayes, M.O., 1994. The Georgia Bight barrier system. In:
R.A. Davis, Jr. (Editor), Geology of Holocene Barrier Island Systems.
Springer-Verlag, Berlin, pp. 233-304.
Hayes, M.O. and Sexton, W.J., 1989. Fieldtrip guidebook T371:
Modern clastic depositional environments, South Carolina. 29th
International Geology Congress, 20-25 July 1989, American Geophysical
Union, Washington, DC, 85 p.
Heinz Center, 2000. Evaluation of Erosion Hazards, A Collaborative
Research Project of the H. John Heinz III Center for Science,
Economics and the Environment. Website at http://www.heinzcenter.org
Henry, V.J., Dean. R.G., and Olsen, E.J., 1987. Coastal Engineering:
Processes, Practices and Impacts. Symposium Series Number 3 of
the Association of Engineering Geologists, 30th Annual Meeting,
Atlanta, Georgia, 58 p.
Howard, J.D. and Frey, R.W., 1980. Holocene depositional environments
of the Georgia coast and continental shelf. In: J.D. Howard,
C.B. DePratter, R.W. Frey (Editors), Guidebook 20: Excursions
in southeastern geology - the archaeology-geology of the Georgia
coast. Geological Society of America Annual Meeting, Atlanta,
Georgia, pp. 66-134.
Nash, J.G., 1977. Historical changes in the mean high water shoreline
and nearshore bathymetry of south Georgia and north Florida. Unpublished
M.S. thesis, University of Georgia, 148 p.
NOAA, 1999. National Oceanographic and Atmospheric Administration
Coastal Futures 2025 Vision. Website at http://coast2025.nos.noaa.gov/htmls/hazards_objs.html
NRC, 1990. Managing Coastal Erosion. National Research Council,
National Academy Press, Washington DC, 182 p.
NSF, 1999. National Science Foundation Community Paper - Sedimentary
systems in space and time: high priority NSF research initiatives
in sedimentary geology. Workshop white paper, 7 p.
NSF, 2000. Coastal Change. National Science Foundation Geology
and Paleontology Program. Website at http://imina.soest.hawaii.edu/Coastal_Conf/PDF/NSF.PDF
NSF-EAR, 1999. National Science Foundation Geology and Paleontology
Program Community Paper - Vision for geomorphology and Quaternary
science beyond 2000, 15 p.
OCRM, 1999. Office of Ocean and Coastal Resource Management, Coastal
Zone Management Program. Website at http://www.nos.noaa.gov/OCRM/czm/welcome.html
Oertel, G.F., 1975. Ebb-tidal deltas of Georgia estuaries. In:
L.E. Cronin (Editor), Estuarine Research Volume 2, Academic Press,
New York, pp. 267-276.
Pilkey, O.H. and Richter D.M., 1965. Beach profiles of a Georgia
barrier island. Contribution 71, University of Georgia Institute
of Marine Science, Sapelo Island, Georgia. Southeastern Geology
6, 11-19.
Rhea, M.W., 1986. Comparison of Quaternary shoreline systems in
Georgia: Morphology, drainage, and inferred processes of formation.
Unpublished M.S. thesis, University of Georgia, 73 p.
Swift, D.J.P., 1991. Sedimentation on continental margins I: a
general model for shelf sedimentation. In D.J.P. Swift,
G.F. Oertel, R.W. Tillman, and J.A. Thorne (Editors), Shelf Sand
and Sandstone Bodies Geometry, Facies, and Sequence Stratigraphy.
International Association of Sedimentologists, Special Publication
14, pp 3-31.
Taylor, L., Harding, J., Henry, V.J., Kelly, J., and Trulli, H.,
1995. Assessment of environmental research and nonmineral resources
offshore Georgia. Georgia Department of Natural Resources, Environmental
Protection Division, Georgia Geologic Survey Project Report 21,
346 p.
Thieler, E. R., and Danforth, W.W. (1994a). Historical shoreline
mapping (I): improving techniques and reducing positioning errors.
Journal of Coastal Research 10(3), 549- 563.
Thieler, E.R., and Danforth, W.W. (1994b). Historical shoreline
mapping (II): Application of the Digital Shoreline Mapping and
Analysis Systems (DSMS/DSAS) to shoreline change mapping in Puerto
Rico. Journal of Coastal Research 10 (3), 600-620.
Thieler, E.R., and Hammar-Klose, E.S., 1999. National assessment
of coastal vulnerability to sea-level rise: US Atlantic coast.
USGS Open-File report 99-593. Website at http://woodshole.er.usgs.gov/epubs/openfiles/ofr99-593/pages/cvi.html
USGS, 2000. US Geological Survey, Coastal and Marine Geology Program.
Website at http://marine.usgs.gov
Research
Projects
Savannah
Inlet and Estuarine Processes Study
The study focuses on the geologic processes which apt to shape
the estuarine/inlet sand-sharing system. The processes that
transport sediment and shape the inlet and estuary are being examined
using side scan sonar imagery, and modern and historic sedimentation
patterns will be determined by seabed sediment sampling and radiochemical
geochronologies. The study will provide information concerning
issues that must be addressed when developing an estuary/inlet
management strategy that is compatible with economic development
and preserving natural resources. The most significant deliverable
from this project will be a preliminary outline that intergrates
our study with the Final Environmental Impact Statement:
Savannah Harbor Long Term Management Strategy Study (August 1996)
prepared by the Savannah District U.S. Corps of Engineers to propose
a framework for a future comprehensive management strategy.
The study is funded through a contract with the Georgia Coastal
Zone Management Program. Dr. Clark Alexander, Associate
Professor at the Skidaway Institute of Oceanography, and Dr. Jim
Henry, Director of the Georgia.
Research on the Floridian Aquifer in coastal Georgia and South Carolina: Mapping the saltwater intrusion threat
The Eocene-Oligocene aged upper Floridan aquifer is the principal source of groundwater in coastal Georgia and is also part of the largest aquifer in the southeastern US. In Georgia, the Miocene aquiclude ("cap rock") overlying the aquifer helps both to retain fresh water in the aquifer and prevent intrusion of seawater. USGS data show that a progressive increase in groundwater use in coastal GA and SC since the late 1800s has led to the development of a large (>5800 km2) asymmetric cone of depression on the aquifer's potentiometric surface that has a radius of 28-60 km, underlies eight contiguous GA-SC coastal counties, and is centered on Savannah, GA. A significant portion of the intracoastal and inner shelf area now lies within this cone of depression. A two-year study is currently being conducted to map intracoastal and inner-shelf areas of Georgia and South Carolina where seawater may intrude into the upper Floridan aquifer. The study is being funded by the Georgia Department of Natural Resources, Environmental Protection Division, as part of an interim strategy to acquire the scientific knowledge fundamental to effective future management of groundwater resources in southeastern Georgia. Geophysical data are being collected with state-of-the-art seismic-reflection, sidescan, and DGPS systems in order to accurately locate areas where: (1) the upper Floridan aquifer is present at shallow depth and (2) the Miocene aquiclude is breached, thin, or missing. Areas of Concern (AOCs) are being defined where these two criteria are met in conjunction with (1) an overlying water column that is saline and (2) a potentiometric surface on the aquifer that is near or below mean sea level. At each AOC, either modern tidal channels or infilled Plio-Pleistocene paleochannels cut into or through the aquiclude to form potential conduits for seawater to enter the aquifer. Tony Foyle, Clark Alexander and Jim Henry are the Co-PI's of this study.