Flood control

Florida would be an entirely different state were it not for flood control. It makes possible the things that Florida has come to be known for: a top tourist destination, a popular spot for wintering residents, a leading agricultural producer, and having thousands of waterfront houses and condos.

During the land boom of the 1920s, developers saw the potential for Florida's muggy swamps and wetlands to be transformed into a hospitable paradise. All that had to be done was to drain the expansive Everglades and figure out how to keep the land under future homes dry and the fields for future crops adequately watered. This vision, coupled with the deadly hurricane flooding of the late 1920s spurred on the drainage and control of south Florida's water.

Kissimme River ditch dug in the early 20th century

Turning the Kissimmee River into
the Kissimmee Canal. Digging ditches
was in response to devastating
flooding that occured in the early part
of the 20th century. See the
Kissimmee River Restoration Project.

Florida's flat topography, heavy rainfall, and impermeable limestone bedrock combine to create land that is highly prone to flooding. Flooding occurs when the ground can't absorb heavy rains, when there isn't enough slope to the land to pull the water away, or when natural waterways can't hold the excess water. All of these factors add up to about 14.25 million acres (41%) of Florida's land being flood prone, according to the Federal Emergency Management Agency.

Flooding is a natural process that has been happening for millions of years. 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 places like south Florida rely almost completely on groundwater for their drinking and domestic water supply needs. Excessive flooding has caused tragic casualties and devastating economic losses throughout Florida's history. To facilitate drainage and to protect property and lives, environmental engineers have devised a complex, connected system of levees, canals, dams, reservoirs, pumping stations, and other water control structures as a means to manage freshwater in Florida. Visit the South Florida Water Management District (SFWMD) and US Army Corps of Engineers (USACOE) South Florida web sites for further information.

These structures provide routes for excess water to either drain into impoundment areas or into the ocean. Such devices are also used to facilitate irrigation for Florida's wide range of agricultural crops, industries, and rapidly increasing residential populations. During the wet season (June-October), the water control structures keep fields and urban areas dry. During the dry season (October-May), the structures supply water for drinking and irrigation.
However, hasty construction in the past has led to negative environmental effects in the present. Today, the employment of water control structures remains a controversial topic in Florida as conservationists clash with developers. In addition to altering habitats, water control devices must be clear of vegetation in order to function properly. The need to consistently manage vegetation in canalways 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 aesthetic value of plant communities.

AQUATIC PLANT MANAGEMENT AND FLOOD CONTROL
The unimpeded flow of water is necessary for canals to carry out their intended function of conveying water. In order for flood control structures to function properly and efficiently, they need to remain free of obstructions such as aquatic plants.

The blockage of canals can hinder navigation, create water supply problems, and contribute to flooding. Dense growths of aquatic plants have been known to block water flow of drainage canals by as much as 95%. By using the equation of Manning's roughness coefficient, this means that only 5% of the intended water capacity is flowing through the canal; or, that the canal is only working at 5% of its intended efficiency. It wouldn't take very much excess water to exceed the handling capacity of that canal. If you were one of the 1.3 million Floridians that live in a flood-prone area, you might want that canal to be working at a greater efficiency so that it can carry more water away from your property during heavy downpours.
Agencies such as the five Water Management Districts, the Department of Environmental Protection, the Army Corps of Engineers, and scores of local governments all share responsibilities in maintaining water control structures. Plant management is an important aspect of keeping these structures working at their intended capacities. Plant managers rely mainly on herbicide treatments to control aquatic invaders like hydrilla. Sometimes water currents prevent the effective use of herbicides and so mechanical controls must be used to clear away aquatic plants.

PURPOSE AND BENEFITS OF FLOOD CONTROL
The overall purpose of flood control structures is to eliminate high and low water periods and create a uniform, manageable water regime. During the development era, regulating and taming the land and water was easier than regulating the human population. Developers decided to dictate where the water went rather than trying to tell people where they could and couldn't settle. The extensive management of Florida's water allowed for the:

growth of the agriculture industry
removal of flood waters
storage of excess water for use during dry periods
prevention of saltwater intrusion by maintaining adequate groundwater levels
protection of residential and urbanized areas
construction of more urban and agriculture in traditional flood plains
expansion of navigation activities
No one thought that with all of these benefits that there could be any negative consequences. It would take several decades to realize that dramatically altering natural water patterns would result in changes in wildlife populations, decreased animal and plant diversity, accelerated growth of algae and invasive plants, and an increase of compounds such as nitrogen and phosphorus. Poorly designed water control systems can also lead to low dissolved oxygen levels, fish kills, and unhealthy plant communities.

The “Kissimmee flood project” of the late 1940s was designed to alleviate flooding in the town of Kissimmee. While, the project has been successful in prevented flooding in and around Lake Toho, Cypress, Hatch and Kissimmee, there have been drastic ecological consequences. Water levels that once fluctuated by as much as 10 feet annually, now fluctuate as little 2-3 feet annually. Impeding water flow also has a profound impact upon 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 the lakes and the surrounding upland, which kept nutrient levels in balance. Also gone are the periodic droughts that allowed for drying, compaction and burning of plant matter of the littoral zones. As a consequence of the flood project, dense growths of native plants and an increase in muck accumulation and floating islands of organics and plants now dominate the once diverse littoral plants community. In effort to restore healthy fish and wildlife habitat, millions of dollars are spent removing tens of millions of cubic yards of sediments from the littoral zones.

AGRICULTURE AND FLOOD CONTROL
Not only is controlling Florida's water regime important to development, but flood control is also vital to Florida's agriculture industry. Growing crops requires scheduled and predictable water patterns so that crops get just 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 a vital component in ensuring that the trees have the best possible growing environment.
The soils in the citrus production areas of the south and southwestern part of the state are naturally sandy and drain poorly. Drainage control structures are required 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 allows for the capturing of enough water to irrigate the majority of Florida's crops. Fields are connected to water supplies through networks of irrigation ditches and canals.

FLOOD CONTROL IS HERE TO STAY
Like it or not, people will keep moving to Florida and crops will keep growing. More flood control structures will be built to accommodate the influx of people and to correct the mistakes of older structures.

The Creators
This page was authored by Becca Hassell
with assistance from Tara Muncaster and Aimee Lyons.
Data is from the APIRS database.
This page was designed and managed by Becca Hassell.
This page is maintained by Alison Moss.

Vic Ramey is the editor.
DEP review is by Jeff Schardt.
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This project is a collaboration of
the Center for Aquatic and Invasive Plants, University of Florida,
and the Bureau of Invasive Plant Management, Florida Department of Environmental Protection

CAIP-WEBSITE@ufl.edu
Copyright 2008 University of Florida