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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

Water and Environmental Stress


Photo of water puddled on exposed soil

Soil Subsidence

The intensive drainage and associated agriculture south of Lake Okeechobee in the EAA has caused a tremendous loss of organic soils. The compaction and oxidation of organic soils in the agricultural lands south of the lake was one of the first observed environmentally destructive effects of large-scale drainage. In most areas, 5 ft or more of organic soil had been lost by 1984 (Stephens and others, 1984). A recent calculated rate of loss in the EAA is about 1 in/yr (Barry Glaz, Department of Agriculture, written commun., 1994). The maximum thickness of this soil, which is underlain by limestone, was initially only 12-14 ft. The process of oxidative loss of soil continues, although the process has been slowed in some locations by reflooding fallow fields and maintaining a high water table.

Such a large loss of soil has affected hydrology and ecology of the Everglades in many ways. The altitude gradient from the upper to the central Everglades has been greatly affected by the soil loss. The loss of altitude has meant a loss of the hydraulic head that once caused water to flow south. The movement of water from north to south now requires pumpage, and the pumpage effort necessary to move water continues to increase with time as the soil continues to subside. The soil loss also has reduced water-storage capacity, which has caused a reduction in the ability of the area to absorb water and mediate seasonal and long-term variations in rainfall. The problems caused by soil loss are magnified by the enormous spatial extent of the loss. In fact, the loss is not confined to the EAA, but actually extends into the northern parts of WCA-1 and WCA-3A, where additional soil has been lost as a result of the diversion of water.


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