Levee

Levee

A Levee is a natural or artificial slope or wall to prevent flooding of the land behind it. It is usually earthen and often parallel to the course of a river in its floodplain or along low-lying coastlines.

Etymology

The word levee, from the French word levée (from the feminine past participle of the French verb lever, "to raise"), originally referred to the raising of a siege by an army. It has since been applied to constructs that prevent flooding.

Natural formation

A natural levee occurs where sediment is deposited on the river bank, raising the level of the land adjacent to the river. This is caused by the slowing of water flow around the bends of a river, which causes sediment to be deposited on the inner side of the bend.

Artificial levees

Artificial levees are typically built by piling earth on a cleared, level surface. The surface is compacted, and a trench is often dug at the foot of the levee to prevent water from seeping under it. The levee is then covered with a layer of clay to prevent erosion, and grass is planted on top to further protect the levee from erosion.

Levee failures

Levees can fail in a number of ways. The most common is a levee breach. A breach can occur if the base of the levee is eroded by water flow, if the levee is overtopped by high water, or if the levee is physically damaged, for example by the impact of debris during a flood.

See also

• Floodplain
• Flood control
• Levee breach
• Coastal management

External links

• Levees.org - Information about the U.S. levee system

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  Cross section of a river levee
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  Levee along the Sacramento River
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  Reinforced embankment at the harbor of Laaxum
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  Broken levee on the Sacramento River
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  Levee in Gretna