Plant Management in Florida Waters
Flood Control
Florida would be an entirely different state were it not for flood control. It has enabled Florida to become a top tourist destination, a popular spot for winter residents, a leading agricultural producer, and a place with thousands of waterfront homes.
During the land boom of the 1920s, developers saw the potential to transform south Florida's muggy swamps and wetlands into a hospitable paradise for people. All that was needed was to drain the expansive Everglades, keep the ground under future homes dry, and the fields for future crops adequately watered. This vision, coupled with deadly hurricanes and flooding in the late 1920s, started the drainage and control of south Florida's waters.
One result of these efforts was turning the Kissimmee River into the Kissimmee Canal. See the Kissimmee River Restoration Project.
Florida's flat topography, heavy rainfall, and limestone bedrock combine to create land that is highly prone to flooding. Flooding occurs when the ground can't absorb heavy rains, and when natural waterways can't hold the excess water. These factors add up to 14.25 million acres (41%) of Florida's land being flood-prone, according to the Federal Emergency Management Agency (FEMA).
Flooding is a natural process. In floodplain ecosystems such as the Everglades, rainfall collects on the surface and drains into the soil, recharging the water supply of the underground aquifer. This is important because Florida relies almost completely on groundwater for drinking and domestic water-supply needs. Excessive flooding has caused death and economic losses throughout Florida's history. To facilitate drainage and to protect property and lives, environmental engineers devised a complex system of levees, canals, dams, reservoirs, pumping stations, and other water-control structures to manage fresh water and provide flood control in Florida.
Water control structures provide routes for excess water to drain into impoundment areas or into the ocean. Such devices also facilitate irrigation for Florida's agricultural crops, industries, and rapidly increasing residential populations. During the wet season (June-October), these water-control structures protect fields and urban areas from flooding. During the dry season (November-May), the structures supply water for drinking and irrigation.
Hasty development in the past has led to negative environmental effects today. The use of flood-control structures remains controversial in Florida, as conservationists clash with developers. Water-control devices must be clear of vegetation, to function properly. The need to consistently manage vegetation in canals adjacent to flood control structures in reservoirs and on rivers can conflict with the desires of anglers and waterfront property owners who may prefer the habitat and aesthetic value of plant communities.
Algae are in the plant kingdom, but technically they are not plants. A diverse group of organisms, algae survive in even the harshest habitats. From the dry desert, to the Arctic Circle, to boiling springs, these organisms have found a way to extract enough from their environment to live. Algae range in size from microscopic to meters long and from single-celled to complex organisms that rival large plants. These organisms may look like true plants, but unlike plants, algae do not have roots or true stems and leaves. In Florida's freshwaters, algae are what make the water green. Green water is not necessarily undesirable, and neither are algae. In fact, algae are essential to the ecosystem and to life as we know it. Algae are a primary component of the food web, providing food for all types of animals, including fish, insects, mollusks, zooplankton (microscopic animals), and humans. There are microscopic algae, like phytoplankton; and there are macroalgae, visible to the naked eye. Algae occur naturally in all types of systems and can indicate the condition of an ecosystem. The mere presence of a species can indicate the amount and type of nutrients present.
 Flood control structure on Lake Okeechobee |  Kissimmee River (1900s) |  Cape Coral, Florida |
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Aquatic Plant Management and Flood Control
The unimpeded flow of water is necessary for canals to carry out their intended function of conveying water. For flood control structures to function properly and efficiently, they must remain free of obstructions such as aquatic plants.
Blocked canals hinder navigation, create water-supply problems, and prevent flood control. Dense growths of aquatic plants can block the water flow of drainage canals by as much as 95%, allowing only 5% of the intended water capacity to flow through the canal 1.3 million Floridians live in a flood-prone area, and need properly functioning water control structures during heavy rains and hurricanes. Agencies such as Florida’s five Water Management Districts, the Florida Department of Environmental Protection, the U.S. Army Corps of Engineers, and scores of local governments all share responsibilities for maintaining water-control structures. Plant management is an important aspect of this maintenance. Plant managers often rely on herbicide treatments to control aquatic plants such as hydrilla. Mechanical control methods are also used to clear away aquatic plants.
Obstructed water flow on Lake Okeechobee
Purpose and Benefits of Flood Control
The overall purpose of flood-control structures is to eliminate high and low water periods and create uniform, manageable water regimes. During the development era of the early 1900s, altering the land and water was allowed and even encouraged to foster economic development. Extensive management of Florida's water allowed for:
- Growth of the agriculture industry
- Abatement of flood waters
- Storage of water for use during dry periods
- Prevention of saltwater intrusion to groundwater
- Protection of residential and urban areas
- Construction of more urban and agricultural areas in traditional floodplains
- Expansion of navigation
With all these benefits, few considered the negative consequences of altering the land and waters of Florida. It took several decades to realize that dramatically altering natural water flows resulted in reduced wildlife populations, decreased animal and plant diversity, accelerated growth of algae and invasive plants, and an increased accumulation of nutrients such as nitrogen and phosphorus. Poorly designed water-control systems can also cause low dissolved oxygen levels in the water, fish kills, and unhealthy plant communities.
The Kissimmee Flood Control project of the late 1940s was designed to alleviate flooding in the town of Kissimmee. While successful in preventing flooding in and around Lakes Toho, Cypress, Hatch and Kissimmee, the project had severe ecological consequences. Water levels that once fluctuated as much as 10 feet annually now fluctuate as little as 2-3 feet annually. Impeding water flow also had a profound impact on other ecological processes, such as nutrient cycling and fire regimes. Gone are the flooding events that effectively thinned native plant communities and carried nutrients and organic debris far from lakes and surrounding uplands. Also gone are the periodic droughts that allowed for drying, compaction, and lightning-ignited burning of plant matter in the littoral zones. As a consequence of the flood control project, dense growths of native and invasive plants, accumulated muck, and floating islands of organic material and plants now dominate the once-diverse plant community. To restore healthy fish and wildlife habitat, millions of dollars have been spent removing tens of millions of cubic yards of these materials from littoral zones.
Visit the South Florida Water Management District (SFWMD) and US Army Corps of Engineers (USACOE) South Florida web sites for further information.
Agriculture and Flood Control
Canal
Flood control is vital to Florida's agriculture industry. Growing crops requires scheduled and predictable water delivery so crops get enough, but not too much, water. The citrus industry is the largest segment of Florida's agriculture and also one of the most susceptible to weather changes. Controlling the water supply to citrus trees is vital in ensuring the best possible growing environment. Soils in citrus-production areas of south and southwest Florida are naturally sandy and drain poorly. Flood-control structures are needed to keep the lands from being submerged during the wet season as the roots of citrus trees cannot tolerate standing water. Controlling water flow also lets us capture enough water to irrigate most of Florida's crops. Fields are connected to water supplies through networks of irrigation ditches and canals.