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Living near water is a wonderful thing—except when there’s a flood. Therefore people build levees. A levee is a natural or artificial wall surface that blocks water from going whereby we don’t want it to go. Dams may be provided to increase obtainable land for habitation or divert a human body of water so the abundant soil that a flow or sea bed may be supplied for agriculture. They protect against rivers native flooding urban in a storm surge. However if a levee breaks, the consequences can it is in disastrous.
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Levees room usually made of earth. The natural movement of a body of water pushes sediment to the side, producing a herbal levee. The financial institutions of a river are frequently slightly elevated native the river bed. The banks kind levees do of sediment, silt, and other products pushed next by the flow water. Dams are typically parallel to the way the river flows, so dams can help direct the circulation of the river.
Levees can additionally be artificially created or reinforced. Artificial levees room usually developed by piling soil, sand, or rocks ~ above a cleared, level surface. In locations where the circulation of a flow is strong, levees may likewise be make of blocks of wood, plastic, or metal. Whereby the area next to a flow or various other body that water is in specific danger, levees may even be reinforced through concrete.
People have been building and reinforcing levees due to the fact that the start of civilization. As beforehand as 2500 BCE, the Indus sink Civilization, v urban centers in what is this particular day Mohenjo Daro and also Harappa, Pakistan, used dams to protect land near the Indus River. Farmers were able come grow plants like cotton and rice.
In enhancement to creating living room and cropland, levees deserve to also provide a measure of protection from invaders. Levees deserve to make a river favor a moat, avoiding people from conveniently invading region on the other side. Ruining levees can likewise stop invading forces. In 1938, Chinese leaders intentionally damaged levees top top the Yellow flow to avoid the Japanese military from advancing. More than 500,000 people, Japanese and Chinese, died in the result flood.
Artificial levees need to it is in protected. They need to stand approximately erosion, or wearing away, by the adjacent water. Sometimes, trees and also plants favor Bermuda grass room planted near levees to anchor the soil. Engineers need to maintain dams with structural work to reinforce the boundaries.
In emergencies, temporary levees have the right to be do of sandbags. These soak increase the water and also usually protect against excess water native seeping past the sand.
Artificial levees prevent flooding. Yet they additionally create a brand-new problem: levees squeeze the flow of the river. All the river’s power is flowing through a smaller space. Water level are higher and water flows faster. This puts much more pressure on dams downstream and makes the water more an overwhelming to control. If dams break, it likewise makes containing the flood an ext difficult.
Since the 18th century, levees have protected Louisiana and also other nearby states indigenous flooding by the Mississippi River. Once Hurricane Katrina struck new Orleans in 2005, the levees might not stand up to the storm surge. The dams broke, and also water flooded 80 percent that the city.
Levees ~ above the Sea
Although most dams exist to manage rivers, they can likewise exist on the coast. The nation of the Netherlands has fancy system that dikes, levees, and also dams to hold earlier the phibìc Sea. Land for farms, industry, and also residential use has actually been developed from land that was once the ocean floor.
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The bay of Fundy, which borders the districts of brand-new Brunswick and also Nova Scotia, Canada, has one that the greatest tidal arrays in the world. The tidal selection reaches an ext than 17 meter (55 feet) in some places. To make the most use of soil that would certainly otherwise it is in underwater throughout high tide, Canada has constructed levees along parts of the just of Fundy.