Devices for Flood Prevention

Americans are well aware of the devastation floods can create. Thousands of lives were lost in the New Orleans floods in 2005. The city was nearly destroyed by the breakage of the levees that were meant to protect the city from floods. Around the world and throughout history controlling water has been a challenge to any society built on flood-prone waterways such as rivers. Flood control methods have changed little through the centuries. A few tried and true methods have been improved by the innovation of newer, stronger materials, such as concrete and steel, but the principles remain the same.

Levees

• The Army Corp of Engineers explains that levees are used to block the flow of water when it rises above the flood stage. Levees are raised barriers of earth that line the bank of the river or stream. The levee can be strengthened or raised when waters rise. Communities often reinforce levees with sandbags when flooding is threatened. Engineers can, to some extent, determine the amount and force of water a levee can withstand. This allows some warning time to people in the path of a flood to prepare for evacuation.

Dams and Locks

• Dams are a primary water control device. They serve to catch and hold water for use as well as flood prevention. Those dams situated at the headwaters of rivers or streams catch heavy runoff. The water is then slowly released and caught again by dams farther downstream. The amount of water entering the main river can be controlled in this way. Dams are sometimes used in conjunction with a system of locks that open and close, controlling the flow of water.

Floodways

• Floodways are a method of flood control that allow for planned flooding. They are used in the Netherlands and have become increasingly popular around the globe. The concept is to divert flood waters over land that is set aside for the purpose. A riverside park, for example, can be flooded to protect a warehouse district. A woodland will be harmed less by flooding than a field of crops. J. Bret Bennington of Hofstra University writes that when a community chooses floodways, it must relocate homes and businesses and allow farmland in the floodplain to revert to wetlands.

Floodwalls

• Large towns and cities with riverside sections that cannot be repurposed often install floodwalls. These are reinforced concrete walls that run for a limited distance on the banks of a river. They are high enough to exceed any possible flood stage on that particular waterway. If the historic flood stage of a river is 30 feet, the floodwall might be built at 50 feet. Floodwalls are useful, but in cases of huge floods, water may be able to rise over them. Should water over-top the floodwall, it can get trapped behind and be unable to return to the channel of the waterway.