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A levee is a natural or artificial flood bank that follows along a river or canal path. Natural ones are created when a river floods over the bank and deposits sediment, which causes the banks to be higher than the floodplain. Man-made barriers are created to prevent flooding, contain water flow, and/or increase water speed.
Also known as a stop wall, dike, dam, or storm barrier, a levee can be found along lakes, rivers, or the sea. Generally made of soil, some man-made levees are reinforced by rocks or concrete to prevent erosion. They are occasionally used as a military defense, as well. There is no set height for such a barrier; the height usually varies between 10 and 30 feet (3 to 10 m). An emergency levee, such as that to be used in the event of flood, can be created with sandbags.
In the Southern and Midwestern areas of the U.S., "levee" is the commonly used term. In Europe and Canada, this structure is most likely to be known as a dike. Although the terms are often used interchangeably, the definition is slightly different. In the Netherlands, a system of dikes diverts flood waters from large bodies of water. Along the Mississippi River, a system of levees restrains flooding waters from lakes and stream. These barriers might also be referred to as embankments.
A levee failure occurs when a break, also known as a breach, occurs. As part of the barrier breaks away, it allows water to flow through the opening. Another type of failure occurs when water flows over the top of the structure. Sand boils, which results when the rising pressure of the water flowing through the pores in the soil is stronger than the downward pressure of the soil, can also occur during a breach.