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Coastal & Marine Geology Program > Center for Coastal and Watershed Studies > Open File Report 01-303

A Summary of Findings of the West-Central Florida Coastal Studies Project

USGS Open File Report 01-303

Purpose & Scope
Strategy, Data,
& Products
Study Area Characteristics
Early Geologic History
Coastal/Inner Shelf System
Study Objectives:
Primary Objectives
Study Findings:
Geologic Template
Infilled Shelf Valleys
Shelf Sedimentary
Hardbottom Development
Barrier Island Studies
Appendix 1
Appendix 2
Appendix 3

The Study Area—Basic Characteristics

The west-central coast of Florida, extending from Anclote Key on the north to Cape Romano on the south (Figure 1) and facing the Gulf of Mexico, is an estuarine, barrier-island, inner-shelf system of marked contrasts, contradictions, and unique characteristics, yet it provides broad applications to understanding other barrier-island systems. It lies between two plant-dominated, sediment-starved, low-wave energy coasts; (1) the open-marine, salt-marsh dominated (Juncus roemerianus) Big Bend coast to the north and (2) the open-marine, mangrove-dominated (Rhizophora mangle) Ten Thousand Island coast to the south (Hine et al., 1988; Parkinson, 1989, Davis et al., 1992; Davis, 1997). As mentioned above, we chose to examine the northern half of barrier chain from Anclote Key, the northernmost barrier island in the chain, to the mainland beach/headland at Venice, FL. In addition, we chose the 20 m isobath, occurring approximately 20 km offshore, as the seaward limit of the inner shelf. This isobath assured that we would be examining at least the past 9,000 years of shelf and coastal evolution based upon most sea-level curves obtained from this part of the world (e.g., Neumann, 1971; Fairbanks, 1989; Wright, 1995).

This coastal/shelfal system offers contrasts and contradictions in that both wave-dominated and tide-dominated coastal features (Nummedal et al., 1977; Hayes, 1979), which are normally widely separated, herein lie closely juxtaposed (Davis and Hayes, 1984; Davis, 1989). The study area is sediment-starved, yet the ebb-tidal deltas associated with several inlets (e.g., mouth of Tampa Bay) are among the largest in the US and provide an enormous source of sand for beach nourishment (Hine et al., 1986). Areas of rapid erosion and rapid accretion may be found adjacent to one another. This coastal system is viewed as generally a low-wave energy system, yet overwash fans, new tidal-inlet cuts, areas of rapid coastal morphologic change, and offshore linear sand ridges with large-scale bedforms are found, all indicating high-energy activity. Additionally, the system is unique in that the sediment is rich in carbonate components (generally molluscan), may be pure carbonate in restricted areas, has Holocene limestone outcroppings, and is underlain in the shallow subsurface by Neogene limestone of a formerly active carbonate platform. This underlying limestone provides a strong, regional, antecedent topographic influence. However, this extreme range of morphologies, products, and processes makes this study area an ideal field laboratory to examine a wide spectrum of natural phenomena, which has broad application to most other barrier island/inner shelf systems.

Finally, this coastal system offers stark contrasts between highly developed, in human habitation terms, and relatively pristine areas and has one of the fastest increase in population anywhere in the US. The study area encompasses parts of five coastal counties whose combined year-round population is over 2,855,154 ( people. This number is increased considerably during the peak tourist season in the winter. The prime attraction to visitors providing an enormous contribution to the local economy are the barrier-island beaches, inlets, lagoons, and associated plant life (marshes, mangroves, seagrass) and animal life (fish, birds). Because of the development pressure placed upon this coastal system and the chronic beach erosion, the State of Florida considers most of the study area to be an area of great concern (Clarke, 1992).

It is our intent that the scientific data and interpretations produced by the West-Central Coastal Studies Project provide critical and important baseline information to all public and private sectors for the proper management of this enormous resource.

Coastal & Marine Geology Program > Center for Coastal and Watershed Studies > Open File Report 01-303

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