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Last edited 03 Nov 2021

Levee

In August 2005, Hurricane Katrina caused levees to break, releasing floodwaters into neighbourhoods in New Orleans, Louisiana. This aerial photograph shows the break in the levee in the 9th ward. Photo courtesy of Jocelyn Augustino/FEMA.

The International Levee Handbook, published by CIRIA in 2013, defines levees as: "Raised, predominantly earth, structures (sometimes called flood defence embankments or dikes) whose primary objective is to provide protection against fluvial and coastal flood events along coasts, rivers and artificial waterways that are not reshaped under normal conditions by the action of waves and currents. Levees form part of flood defence systems that may also include flood walls, pumping stations, closure structures, natural features, etc."

As stated in the CIRIA definition (and outside of engineering applications), the terms levee and dyke are sometimes used interchangeably, but they are not technically the same.

Dykes are usually permanent structures that are built in areas that are located below sea level and are thus uninhabitable. Their placement reclaims land to make it fit for use. Levees can be permanent structures, such as those built from cement, or temporary structures which might be made from stone, earth or sandbags, and protect from flood.

There are also geographic/cultural preferences. For instance, in the state of Louisiana (which is vulnerable to flooding of rivers prompted by hurricanes), the term levee is most frequently used. In the lowlands of the Netherlands (which have been reclaimed from the sea), dyke is the common term.

See dyke.

In Ancient Egypt, levees were used along the Nile to protect the surrounding valleys and to irrigate the land. They were also used in other Ancient cultures such as Mesopotamia, where farmers built earthen levees to prevent rivers from flooding their fields.