155—Southern Florida Flatwoods

This MLRA (shown in blue in the figure above) is entirely in Florida. It makes up about 18,575 square miles (48,135 square kilometers). Numerous cities occur in this area. Gainesville and Ocala are in the isolated northern part of the area. Daytona Beach, West Palm Beach, and Fort Lauderdale are on the Atlantic coast, which forms the eastern boundary of the area. The cities of St. Petersburg and Fort Meyers and most of Tampa Bay are on the western edge of the area, along the coast of the Gulf of Mexico. The eastern half of the city of Orlando is in this MLRA. Interstate 75 parallels the Gulf coast in the western half of this MLRA, and Interstate 95 parallels the Atlantic coast in the eastern half. Interstate 4 crosses the northern end of both the eastern and western parts of this area. Cape Canaveral and the John F. Kennedy Space Center are in this MLRA.

Physiography

This area is in the Floridian Section of the Coastal Plain Province of the Atlantic Plain. It is on a nearly level coastal plain that has large areas of swamps and marshes. Streams and lakes are common. The northwestern half of Lake Okeechobee occurs in this area. Its surface is 14 feet (4 meters) above sea level. Most of the area is flat, but some hummocks rise 3 feet (1 meter) above the general level of the landscape and low beach ridges and dunes, on each coast, rise 6 to 10 feet (2 to 3 meters) above the lower inland areas. Elevation ranges from sea level to less than 80 feet (25 meters), increasing gradually from each coast inland.

The extent of the major Hydrologic Unit Areas (identified by four-digit numbers) that make up this MLRA is as follows: Southern Florida (0309), 40 percent; St. Johns (0308), 32 percent; Peace-Tampa Bay (0310), 27 percent; and Suwannee (0311), 1 percent. The St. Johns, Kissimmee, and Caloosahatchee Rivers are in this area.

Geology

This area is a young marine plain underlain by Tertiary-age rocks, including very fine grained shale, mudstone, and limestone beds. A sandy marine deposit of Pleistocene age occurs at the surface in most of the area.

Climate

The average annual precipitation in this area is 44 to 60 inches (1,120 to 1,525 millimeters). About 60 percent of the precipitation occurs from June through September. Most of the rainfall occurs as moderate-intensity, tropical storms that produce large amounts of rain from late spring through early autumn. Late autumn and winter are relatively dry. The average annual temperature is 68 to 75 degrees F (20 to 24 degrees C). The freeze-free period averages 335 days and ranges from 300 to 365 days.

Water

Following are the estimated withdrawals of freshwater by use in this MLRA:

Public supply—surface water, 3.7%; ground water, 15.1%
Livestock—surface water, 0.2%; ground water, 1.4%
Irrigation—surface water, 21.4%; ground water, 35.6%
Other—surface water, 14.2%; ground water, 8.4%

The total withdrawals average 3,500 million gallons per day (13,250 million liters per day). About 60 percent is from ground water sources, and 40 percent is from surface water sources. Rainfall and surface and ground water sources provide an abundance of water. Canals and ditches control the ground water level for crops and pasture. Excess water is pumped out during the rainy season, and irrigation water is applied during the growing season. The surface water is of good quality.

Most of the domestic, municipal, and irrigation water in the area is obtained from wells in the artesian Floridan aquifer, which consists of deep limestone and dolomite beds. This aquifer is one of the most productive ground water sources in the United States. The water from this aquifer is a calcium bicarbonate type. It is hard, and it has high amounts of total dissolved solids in some areas.

A source of drinking water in this area is a nonartesian aquifer of sand, shells, and limestone that occurs in a belt across the southern and central parts of this MLRA. This shallow aquifer provides limited quantities of good-quality water. The water is a calcium bicarbonate type that is hard or very hard. It is highly susceptible to contamination from surface activities.

Soils

The dominant soil orders in this MLRA are Alfisols, Entisols, and Spodosols. The soils in the area dominantly have a hyperthermic soil temperature regime, an aquic soil moisture regime, and siliceous mineralogy. They generally are deep or very deep, poorly drained or very poorly drained, and loamy or sandy. Endoaqualfs (Holopaw and Malabar series) and Glossaqualfs (Pineda and Riviera series) formed in loamy marine sediments on flats and flood plains and in depressions. Alaquods (Eaugallie, Immokalee, Myakka, Oldsmar, Smyrna, and Wabasso series) and Psammaquents (Basinger series) formed in sandy marine deposits on flats and flood plains and in depressions.

Biological Resources

This area supports “flatwood” forest vegetation. Slash pine, longleaf pine, cabbage palm, and live oak are the principal species. Saw palmetto, gallberry, and grasses, such as bluestems and wiregrasses, characterize the understory.

Some of the major wildlife species in this area are white-tailed deer, feral hog, bobcat, squirrel, snipe, raccoon, skunk, otter, bobwhite quail, woodpecker, and mourning dove. The species of fish in the area include black crappie, largemouth bass, bluegill, and catfish.

Land Use

Following are the various kinds of land use in this MLRA:

Cropland—private, 7%
Grassland—private, 36%
Forest—private, 19%; Federal, 3%
Urban development—private, 17%
Water—private, 13%
Other—private, 5%

The forestland in this area consists mainly of low-quality pine. It is grazed extensively. More than one-third of the area is improved pasture or native range grazed by cattle. The limited acreage of cropland in the area is used mainly for many kinds of winter vegetables. Some citrus fruits are grown in the area, and other subtropical fruits are grown in the southern part of the area.

The major soil resource concerns are wind erosion, maintenance of the content of organic matter and productivity of the soils, and management of soil moisture. Conservation practices on cropland generally include conservation crop rotations, cover crops, irrigation water management (including microirrigation systems), nutrient management, and pest management. Conservation practices on pasture and rangeland generally include prescribed grazing, brush management, pest management, prescribed burning, and watering facilities. Conservation practices on forestland generally include forest stand improvement, forest site preparation, prescribed burning, firebreaks, establishment of trees and shrubs, pest management, and management of upland wildlife habitat.

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