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A Region Under Stress-- Home
A Region Under Stress-- Introduction

Environmental Setting-- The Natural System
Physiography
Climate
Geology
Hydrology
Watersheds and Coastal Waters

Environmental Setting-- The Altered System
Drainage and Development
Public Lands
Agriculture
Urbanization
Water Use
Water Budget

Water and Environmental Stress
Loss of Wetlands and Wetland Functions
Soil Subsidence
Degradation of Water Quality
Mercury Contamination
Effects on Estuaries, Bays, and Coral Reefs

Summary and Research Needs
References

Related Links

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U.S. Department of the Interior
U.S. Geological Survey
Circular 1134

The South Florida Environment - A Region Under Stress

Environmental Setting--
The Natural System


Photo of scientist collecting data


The south Florida ecosystem formed during the last several thousand years after the world-wide climatic changes and sea-level rise at the end of the Pleistocene age. The ecosystem consists primarily of wetlands and shallow- water habitats set in a subtropical environment.

Physiography

Physiographic provinces of south Florida
Figure 4. Physiographic provinces of south Florida. (Modified from Davis, 1943; and Parker and others, 1955.) (above) Click on image to open larger picture (35.7k).
Topography and bathymetry
Figure 5. Generalized topography and bathymetry in south Florida. (Topography generalized from U.S. Geological Survey 1:24,000 quadrangles provided in digital form by South Florida Water Management District, 1992. Bathymetry modified from Fernald, 1981.) (above) Click on image to open larger picture (58.8k).


The south Florida ecosystem includes coastal waters between Charlotte Harbor on the Gulf of Mexico and the St. Lucie River on the Atlantic Ocean and all or part of the following physiographic provinces: the Lake Wales Ridge, the Flatwoods, the Atlantic Coastal Ridge, the Big Cypress Swamp, the Everglades, the Mangrove and Coastal Glades, and the Florida Keys (fig. 4). The coastal waters consist of a system of interconnected estuaries, bays, lagoons, and coral reefs that include Charlotte Harbor, Ten Thousand Islands, Whitewater Bay, Florida Bay, Biscayne Bay, and the Florida Reef Tract (fig. 1).

The highest altitude in the region is on Lake Wales Ridge, where sand hills range from 70 to 300 ft above sea level (fig. 5). Adjacent to the ridge, the relatively lower Flatwoods range in altitude from about sea level to 100 ft in the north.

The Atlantic Coastal Ridge extends along the eastern coast as a low ridge of sand over limestone that ranges in altitude from about 10 to 50 ft above sea level. The ridge averages about 5 mi wide and is breached in places by shallow sloughs or transverse glades.

The Everglades, which is located west of the Atlantic Coastal Ridge, is slightly lower in altitude than the ridge or the Flatwoods and extends southward from Lake Okeechobee to the Mangrove and Coastal Glades near Florida Bay. The Everglades has an almost imperceptible slope to the south, which averages less than 2 in. per mile. Altitudes range from 14 ft near Lake Okeechobee to sea level at Florida Bay. Under predeveloped conditions, the Everglades was seasonally inundated, and water drained slowly to the south through what was referred to as the "River of Grass" by Florida author and conservationist Marjory Stoneman Douglas.

The Big Cypress Swamp to the west of the Everglades is on slightly higher land. Water inundation and peat deposition in the swamp are less extensive than in the Everglades. The land surface of the swamp is flat except for numerous low-mounded limestone outcrops and small, circular, elongated depressions in the limestone. Water in the swamp drains slowly to the south and southwest through a number of cypress strands into the coastal mangrove forest.

The Mangrove and Coastal Glades consists of a broad band of swamps and marshes south of the Everglades and the Big Cypress Swamp. The land is at or near sea level and is often flooded by tides or by freshwater runoff. Salinities range from freshwater to hypersaline, depending on the amount rainfall and runoff, and on tide levels. The gradual slope of the land continues offshore across the broad west Florida platform into the Gulf of Mexico. Much of the southern Florida Gulf Coast receives low wave energy which is favorable to the development of tidal marshes, seagrass beds, and mangrove forests.

The Florida Keys are a series of low limestone islands that extend 140 mi southwest of the mainland. Altitudes in the islands rarely exceed 5 ft above sea level. A narrow shelf is present along the Atlantic Coast, where the seafloor drops sharply into the Straits of Florida. The Atlantic Coast is bathed in the clear, tropical waters of the Florida Current which is favorable to the development of coral reefs several miles offshore of the keys.


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