USGS:Science for a changing world
Geologic Division

West-Central Florida Erosion Study

Project Leader:
Guy Gelfenbaum
600 Fourth Street South, St. Petersburg, FL 33701-4846
E-mail: ggelfenbaum@cfcg.er.usgs.gov
Phone: (813) 893-3100 ext. 3017
Fax: (813) 893-3333

The Issue

The state of Florida is highly dependent upon its coastline and coastal ocean for its economic and social well-being. The west-central portion of the coast is characterized by sandy barrier islands with numerous inlets (Fig. 1), and a relatively low wave and tidal energy regime. Despite the low average energy, this coast is highly dynamic, changeable, and subject to erosion (Balsillie and Clark, 1992). Along portions of the west-central Florida coast, approximately 62% of the beaches are cited as "critical erosion areas" (Clark, 1992). In fact, many of the beaches along this coast have undergone renourishment that has cost tens of millions of dollars. What processes are important for the large rates of beach loss in this area? What areas of the coastline are likely to experience erosion in the future? Are there antecedent structural controls on the present day position or future fate of the barrier islands? These and numerous other fundamental questions must be addressed in a systematic, regional approach to improve our understanding of the complex barrier island and inlet system of west-central Florida.

Despite past efforts by state and local agencies, there is not a broad data base nor understanding necessary to supply planners and legislators with regional projections and predictions needed to cope with future coastal management problems. To supply this needed regional data and understanding, congress requested (starting in FY94) the USGS Marine and Coastal Geology Program, formerly the National Coastal Geology Program, to undertake a cooperative study with researchers at the University of South Florida.

How the USGS is addressing this issue

The overall objective of this study is to improve our understanding of coastal processes to provide the basis for long-term management and protection of the beaches, inlets and other coastal resources. Objectives include:
  • To understand the geologic control on the position and development of the barrier islands and tidal inlets of the west-central Florida system,
  • To determine a regional sediment budget which will identify the sediment sources, sinks, accumulation rates, and pathways,
  • To determine the effects of past and present geologic and oceanographic events that might control the morphology and sedimentary processes of the coastal system.

This information will be used to describe past trends, identify important geological and physical processes and make predictions about future shoreline and bathymetric change.

The overall strategy for this study has been to divide the work elements into the following four categories:

  • Data Base/GIS
  • Geologic Framework
  • Processes
  • Morphodynamics
The strategy for the Data Base element has been to work closely with known users of the information from this study to develop and populate a GIS that would assure ease of transfer of project results at the conclusion of the study. Because very little was known about the Geologic Framework and the physical oceanographic Processes of the west-central Florida inner shelf, the strategy for these elements was to begin with reconnaissance level mapping and data collection. Those efforts would phase into more site specific, or hypothesis specific studies. The Morphodynamics of the barrier islands and inlets in the northern section of the study area have been somewhat studied, but there have been very few studies in the southern section. The strategy for this element has been to concentrate on detailed mapping and stratigraphic studies of barrier forming processes.

1998 Activities

FY98 will be the last year of the West-Central Florida Erosion Study. Efforts will concentrate on analysis of field data, writing reports, producing maps, and writing journal articles. Workshops and meeting presentations will also be mechanisms to disseminate information. Some field work will be necessary to tie up loose ends, and to finish existing experiments and data collection. Collaboration of investigators on maps, and models will be the highest priority task in the final year of the study. Some funding will be required to make the Data Base/GIS available to state and local users.

Accomplishments to Date

A sampling of accomplishments are listed below. Similar accomplishments are described separately by each collaborator in project proposals available from the Project Chief.

  • Deployed a pilot mooring at a mid-shelf location to initiate a long time series and test mooring behavior. These data, along with SST, coastal sea level and winds comprise our initial data set (Weisberg et al., 1996a). Some of the findings are presented in Weisberg et al. (1996b) and a more complete analysis will form Mr. B. Black's M.S. thesis.
  • Deployed a trans-shelf array of moorings between the near shore and the shelf slope. A data report (Weisberg et al 1997a) is in press and this data set is being analyzed as part of Mr. E. Siegel's M. S. thesis.
  • Developed a numerical circulation model of the West Florida continental shelf for use in Eulerian and Lagrangian studies of the large scale shelf circulation and smaller, regional scale studies. Yang et al. (1997. Experiments using prototypical weather fronts and cyclone passages have also been performed, along with a simulation of. These experiments are part of Z. Li's Ph.D. dissertation and two scientific papers are in preparation (Li and Weisberg, 1997a, b - first drafts completed).
  • Collected satellite SST images for interpretation relative to the moored and shipboard measurements and interact with SEAWIFS investigators once those ocean color data become available.
  • As part of the total 113 vibra-cores collected for this study, 21 cores were obtained in the Indian Rocks beach mosaic area to specifically describe the lithology and sedimentary history of the sediment ridges.
  • Seven sedimentary facies have been described in the cores from the west Florida inner shelf.
  • Four bathymetric surveys have been collected in the transverse bar field off Anna Maria. Comparison reveals significant movement of the bars. Profiling current meters have been deployed for 50 days during the fall/winter to observe the flow field during the passage of cold fronts.

USGS Cooperators

  • Dr. Albert Hine, USF, Marine Sciences, framework
  • Dr. Stan Locker, USF, Marine Sciences, framework
  • Dr. Larry Doyle, USF, Marine Sciences, framework
  • Dr. Bob Weisberg, USF, Marine Sciences, processes
  • Dr. H. Yang, USF, Marine Sciences, processes
  • Dr. Richard Davis, USF, Geology Department, morphodynamics
  • Dr. Gregg Brooks, Eckerd College, framework
  • Doug Wilson, USGS/USF, processes
  • Dr. Dave Twichell, USGS, framework
  • Ann Gibbs, USGS, morphodynamics
  • Dr. Norm Blake, USF, Marine Sciences, Carbonate Production
  • Mark Hansen, USGS, Database/GIS
    [USF=University of South Florida]

Products

Publications
  • Weisberg, R. H. 1994: Transport of Mississippi River water to the West Florida shelf. Special NOAA Rep., Coastal oceanographic effects of summer 1993 Mississippi River flooding, M. J. Dowgiallo, ed., NOAA Coastal Ocean Office, March 1994, pp55-59.
  • Weisberg, R. H., B. Black and H. Yang (1996) Seasonal modulation of the West Florida continental shelf circulation. Geophys. Res. Lett., 23, 2247-2250.
  • Yang, H. and R. H. Weisberg (1997). West Florida continental shelf circulation response to climatological wind forcing (submitted to Jour. Geophys. Res.)
  • Harrison, S.E., Locker, S.D., Hine, A.C., and Twichell, D.C., submitted, Side scan mosaics of inner shelf sand ridges: new view of an old problem: Geology.
  • Li, Z. and R. H. Weisberg (1997a). West Florida continental shelf response to upwelling favorable wind forcing, Part 1: Kinematics. (in preparation, draft complete).
  • Li, Z. and R. H. Weisberg (1997b). West Florida continental shelf response to upwelling favorable wind forcing, Part 2: Dynamics. (in preparation, draft complete).
  • Weisberg, R. H., B. Black and Z. Li and H. Yang (1997). A case study of upwelling along the west Florida coast. (in preparation)

Completed Theses

  • FitzGerald, M. V., 1995, Stratigraphy of tidal and fluvial paleochannel sequences beneath west-central Florida Gulf Coast barrier islands. Unpublished M.S. thesis, Univ. South Florida, 134 p.
  • Kowalski, K. A., 1995, Morphodynamics and stratigraphy of Big Sarasota Pass and New Pass ebb-tidal deltas, Sarasota County, Florida, 144 p.
  • Pekala, John M., 1995. Stratigraphy and Geologic History of Anna Maria Island, Manatee County, Florida. Unpubl. M.S., Univ. of South Florida, 144p.
  • Sedgwick, P. E., 1995, Stratigraphy of washover deposits in Florida: implications for recognition in the stratigraphic record. Unpubl. M.S. thesis, Univ. South Florida, 160 p.
  • Harrison, S.E., 1996, Morphology and evolution of a Holocene carbonate/siliclastic sand ridge field on the central-west Florida inner continental shelf: Unpub. M.S. thesis, Department of Marine Science, University of South Florida, 211p.

Data Reports

  • Gelfenbaum, G., 1997, Second west-central Florida coastal studies workshop, USGS OFR-97-51, pp 140.
  • Weisberg, R. H., B. D. Black, J. C. Donovan and R. D. Cole (1996). The west-central Florida shelf hydrography and circulation study: a report on data collected using a surface moored acoustic Doppler current profiler, October 1993-January 1995. DMS-USF Tech. Rep., Jan. 1996
  • Weisberg, R. H., E. M. Siegel, B. D. Black, J. C. Donovan and R. D. Cole (1997). The west-central Florida shelf hydrography and circulation study: a report on data collected using a trans-shelf array of acoustic Doppler current profilers, January 1995 -February 1996. DMS-USF Tech. Rep., April 1997.

Presentations at Meetings with Published Abstracts

  • Black, B. D., R. H. Weisberg and H. Yang (1996). Observations of currents over the West Florida continental shelf. Ocean Sciences '96, San Diego CA., Feb. 12-16, 1996
  • Duncan, D.S, Locker, S.D., and Brooks, G.R., 1996, Mixed Carbonate-Siliciclastic Infilling of a Neogene Carbonate Shelf Valley System: Tampa Bay, West-Central Florida. Geol. Soc. Amer. Abs. w/Prog., Annual Meeting.
  • Harrison, S.E., Locker, S. D., Hine, A.C., Naar, D.F., Twichell, .C., 1996, Morphology and Evolution of a Holocene Carbonate/Siliciclastic Sand Ridge Field, Sand Key, West-Central Florida, Geol. Soc. Amer. Abs. w/Prog., Annual Meeting, p. A-43.
  • Hine, A.C., Locker, S. D., Harrison, S.E., Brooks, G., Twichell, D.C., and Davis, R.A., Jr., 1996, West Florida inner-shelf provinces--links to present coastal system and to the geologic past: Tampa BASIS 3 Program, Oct 21-23, Clearwater, FL, p. 7,8.
  • Hine, A.C., Locker, S.D., Harrison, S.E., Brooks, G., Twichell, D.C., and Davis, R.A. Jr., 1996, West Florida Inner Shelf Provinces--Links to Present Coastal System and to the Geologic Past. Geol. Soc. Amer. Abs. w/Prog., Annual Meeting, p. A-43.
  • Locker, S.D. and Hine, A.C., 1996, West-Central Florida Coastal Studies Project – Regional Geologic Framework. Tampa BASIS 3, Clearwater, FL.
  • Yang, H., R. H. Weisberg and B. D. Black (1996). Three dimensional modeling of the West Florida continental shelf circulation. Ocean Sciences '96, San Diego CA., Feb. 12-16 1996
  • Li, West Florida continental shelf. 1996 fall annual meeting of the American Geophysical Union, San Francisco, CA., Dec. 15-19, 1996.
  • Yang, H., R. H. Weisberg Z. Li and B. D. Black (1997). Observations and model studies on the West Florida continental shelf circulation. IAMAP/IAPSO Joint Assemblies, Melbourne, Australia, July 1-9, 1997

Planned Products

  • Twichell, The field tapes of the Sarasota sidescan sonar data, edited navigation, and edited bathymetry will be archived on CD-ROMs as a USGS Open-File Report, and released to NGDC.
  • Twichell, USGS Miscellaneous Field Studies Map showing the Sarasota sidescan sonar mosaic, preliminary interpretive maps of the surficial and shallow subsurface geology, and descriptive text.
  • Twichell, Gelfenbaum, and Brooks, Outside journal publication on the interaction of carbonate and siliciclastic sediments in this inner shelf environment.
  • Davis, R. A., Cuffe, C. K., Kowalski, K. A. and Shock, E. A., Stratigraphic models for microtidal tidal deltas based on Florida Gulf Coast examples. To be submitted to the Journal of Sedimentary Geology.
  • Sedgwick, P. E. and Davis, R. A., Stratigraphic models of washover fans. To be submitted to Journal of Sedimentary Research.
  • Bedrock map of the upper Miocene surface throughout the study area (jointly with Dr. S. Locker and Dr. A. C. Hine).
  • Maps of surface sediment types and composition of the entire study area (jointly with Dr. G. Brooks and Dr. L. J. Doyle).
  • Gelfenbaum, G., and Brooks, in prep, Migration of shore-normal bars: Geology.
  • Brooks , Doyle, and Gelfenbaum, Open-file report on surficial sediments.
  • Brooks, DeWitt, and Doyle, Open-file reports on vibracore data.
  • Locker, S.D., G.R. Brooks, S. Harrison, G. Gelfenbaum, and A.C. Hine, in prep, Bottom Character and Sediment Distribution Patterns off the Indian Rocks Beach Headland, West Central Florida. Journal of Coastal Research.
  • Harrison, S.E., Locker, S.D., and Hine, A.C., in progress, Geometry, bedform distribution, sedimentology, and stratigraphy of inner shelf sand ridges: implications concerning evolution and sediment transport: Marine Geology.
  • Locker, Harrison, and Hine, Misc. Maps of Indian Rocks Beach side-scan mosaic with text and of Indian Rocks Beach sediment thickness and bottom character.
  • Side-scan mosaic of area off Tampa Bay ebb delta.
  • Gelfenbaum and Geraghty, Open file Report map series of coastal structures on the west-central Florida barrier islands.
  • Regional map products:
    • Side-Scan Sonar Imagery and Bottom Types Of the West-Central Florida Inner Continental Shelf. This 5 sheet map series includes all raw sonar imagery and interpretations along with summary comparison to surface sediment mapping.
    • Seismic Stratigraphic Framework - Bedrock Structure and Sediment Thickness Patterns. This map series presents line-drawing interpretations of seismic profiles with reference to coring results.
    • Transect Maps Series. This map series is based on construction of across-shelf transects that integrate all available data sets for comparison. Transects run from the offshore limit of the study area, through the barrier islands, to the bedrock or mainland outcrop. Data will be presented for a 2 mile swath along the transect.

Planned Dissertations and Theses:

  • Zhenjiang Li, Ph.D.
  • Bryan Black, M.S.
  • Eric Siegel, M.S.
  • Jack Parrish, M.S.
  • Brian Donahue, M.S.
  • Jim Edwards, M.S.
  • Tom Ferguson, M.S.
  • Jennifer Kling, M.S.
  • Darren Spurgeon, M.S.
  • Kristin Yale, M.S.
  • Greg Berman, Senior Thesis
  • Steve Obrochta, Senior Thesis

U.S. Department of the Interior, U.S. Geological Survey, Center for Coastal Geology
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Updated: 16 March, 1998@11:40:59 AM (THF)