Working With Nature
Natural flood protection can be attained by protecting and restoring wetlands and floodplains, and by restoring a river’s natural flow and meandering channel. Giving at least some floodplain back to a river will give the river more room to spread out. Furthermore, wetlands act as natural sponges, storing and slowly releasing floodwaters after peak flood flows have passed. A single acre of wetland, saturated to a depth of one foot, will retain 330,000 gallons of water enough to flood thirteen average-sized homes thigh-deep. Coastal wetlands reduce storm surge and slow its velocity.
Maintaining and restoring healthy rivers, wetlands, and floodplains provides a host of other benefits as well. These systems:
Provide Clean Water
Wetlands and floodplains serve as natural filters, absorbing nutrients and other pollutants from water and making rivers healthier for drinking, swimming, and supporting plants and animals.
Floodplain trees and plants anchor river banks, preventing bank erosion. Erosion can lead to increased flood heights, as sediment raises the level of the riverbed as it settles. Excess sediments can also cloud river water and coat the leaves of aquatic vegetation, depriving them of sunlight. Too much sediment also directly impacts human health by fostering the growth of bacteria.
Sustain Commercial Fisheries
Wetlands and floodplains support a multitude of animal life that is the mainstay of the nation’s multi-billion dollar fisheries industry.
More than 82 million hunters, fishermen, bird enthusiasts, and photographers spend $59.5 billion in the United States each year.
Provide Vitally Important Habitat
Seasonally inundated wetlands are some of the most biologically productive ecosystems in the world. More than one-third of federally threatened and endangered species live only in wetlands, and up to 43 percent of them rely directly or indirectly on wetlands for their survival. Over 70 percent of all vertebrate species rely upon the land along the river’s edge, the riparian zone, during their life cycle.
The value of natural flood protection is particularly striking when compared to the record of structural efforts. Despite spending $45.2 billion federal tax dollars $123 billion adjusted for inflation on structural projects nationwide, flood damages continue to rise. Dams, dikes, levees, and floodwalls typically cause severe environmental harm that eventually make flooding worse, and often do not provide the promised levels of protection. Engineered structures:
Can and Do Fail, Often With Catastrophic Results
Before flood control structures, high water events resulted in gradual rises in water. With flood control structures in place, the river can explode through the dam or levee with deadly force. Sometimes, structural projects will not keep a community safe even if it has been properly designed, constructed, and maintained, because such projects are designed to provide only a certain level of protection.
Increase Flood Heights
Levees and floodwalls unnaturally constrict rivers within a narrow channel, causing the waters to rise higher and flow faster than they otherwise would. This leads to more powerful and rapid flooding.
Lure People Into Harm’s Way
Structural flood protection provides a false sense of security about living in the floodplain, which can lure people into high-risk areas. When rivers rise, as they inevitably will, those within the floodplain can quickly become victims.
Destroy Systems That Provide Natural Flood Protection
Levees separate the river channel from its floodplain, starving wetlands of water and the entire river basin of soil and nutrients. Dams, dikes, reservoirs, and detention basins block the flow of sediment and bed material that are necessary to sustain downstream wetlands. Levees, floodwalls, and concrete-lined riverbeds shoot sediments into open water before they can settle at the river’s mouth.
Damage The Health Of Rivers And The Wildlife That Depend On Them
Flood control structures have severe impacts on the downstream hydrologic cycle and ecosystem. Floods are vital to sustaining the health of rivers and are the major force controlling life in river systems. Floods create fertile soil for farming and form islands and backchannels that are home to fish, birds, and other wildlife. Floods check and balance aquatic and floodplain populations and flush out exotic species. Fish that travel upstream to spawn, like salmon and sturgeon, receive reproductive cues from high water and cooler temperatures.