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Encyclopedia of Climate Change, Third Edition

Levees

by Anna M. Cruse

Category(s): Economics, industries, and products

Levees are embankments or engineered structures near bodies of water; they are designed to prevent flooding of the land behind them. Permanent levees are used along rivers and in coastal areas. A breech occurs when a section of levee is washed away, letting water onto the adjacent land.

Key Concepts

abutment: a bracing feature built onto a levee at right angles to the main direction of the levee (a T-shape), its purpose is to provide support for the levee against the pressure applied by the rising floodwater

floodplain: the relatively low area adjacent to a watercourse or a body of water that will become flooded when the water level of the neighboring body of water becomes higher than its banks can contain

DEFINITION

Levees are embankments or engineered structures near bodies of water; they are designed to prevent flooding of the land behind them. Permanent levees are used along rivers, such as the Mississippi and Sacramento Rivers, and in coastal areas, such as New Orleans, Louisiana. Once constructed, levees are protected from erosion by planting them with vegetation such as grass or willows on the river side. Concrete abutments may also be used on the river side of a levee to protect the structure from strong currents. A breech occurs when a section of levee is washed away, letting water onto the adjacent land. On large floodplains, levees are built in a series, stepping back from the river, to provide an extra measure of protection against a breech. Levee systems along coasts and rivers are built and maintained by a variety of state and federal agencies, including the U.S. Army Corps of Engineers (USACE), state and tribal levee boards, and private groups. For example, in Missouri, a group of private landowners who own a majority of the land in a wetland or another region where flooding occurs may create their own levee district, obligating themselves to pay taxes to finance the building and maintenance of levees.

The National Levee Safety Act (NLSA) of 2007 includes several provisions related to the oversight of levee safety and maintenance—including of nonfederal (state and private) levees. One provision of the NLSA authorizes the USACE to develop a plan to create a national levee safety program and to inventory and inspect all federal levees. Nonfederal levees can be added to the USACE inspection and inventory program at the request of local levee boards, but the maintenance and safety of those levees remains the responsibility of the local board. The NLSA also created a National Committee on Levee Safety (NCLS), which consists of representatives from USACE; the Federal Emergency Management Administration (FEMA); and state, regional, and tribal levee boards and is charged with creating a national levee safety program.

Levee reinforcing.

Climate3_p0815_0001.jpg

Photo via iStock/DigiClick. [Used under license.]

SIGNIFICANCE FOR CLIMATE CHANGE

The U.S. levee system is a large, complex patchwork of many different structures that have been built by a variety of organizations over many years. Some of the oldest levees in the United States were built more than 150 years ago. Most levees are earthen structures, built with a tapered profile, at a width-to-height ratio of seven to one. Thus, a maximum height must be determined by the time construction begins, based on analysis of historical data regarding maximum local flood heights and storm surges and the recurrence interval of these events.

Results of climate models, notably those used by the Intergovernmental Panel on Climate Change (IPCC), predict that future increased global temperatures will lead to higher sea levels, increased precipitation rates, and a greater potential for large hurricanes. Also, a report released by Environment Texas in 2007 concluded that weather data from 1948 to 2006 demonstrated that extreme precipitation events had increased by 24%. Together, such weather events have the potential to lead to higher flood levels and storm surges. For example, during the Upper Mississippi Valley flood of June, 2008, peak flows were approximately 1.8 meters above those previously recorded. The storm surge from Hurricane Katrina on August 29, 2005, was 7.6 meters. A report by University of California, Berkeley, scientists concluded that flooding in New Orleans was a result of the levees not being built high enough; however, this conclusion has been disputed by the USACE and independent investigators. Following Hurricane Katrina, the United States Congress passed the Water Resources Development Act of 2007, which authorized creation of the National Levee Safety Program. The law mandated the formation of the National Committee on Levee Safety. The direct effects of global warming on levee safety have not been considered in initial plans for levee safety standards. A further concern for levee safety in coastal Louisiana, and in other cities located on deltas, is the combined effects of ground subsidence and projected sea-level rise. One potential solution is to replace levees with other flood control technologies, such as the movable water gates employed in Japan, England, and the Netherlands.

Further Reading

1 

Cech, Thomas V. Principles of Water Resources: History, Development, Management, and Policy. John Wiley & Sons, 2005.

2 

Degoutte, Gérard and Rémy Tourmont. Spillways on River Levees. Quae, 2021.

3 

Fischetti, Mark. “Protecting New Orleans.” Scientific American 294, no. 2 (February, 2006): 64-71.

4 

Guyer, J. Paul, ed. An Introduction to Levee Construction. Guyer Partners, 2017.

5 

———. An Introduction to Levees. Guyer Partners, 2017.

6 

———. An Introduction to Special Features of Levees. Guyer Partners, 2017.

7 

Intergovernmental Panel on Climate Change. Climate Change, 2007—The Physical Science Basis: Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Edited by Susan Solomon et al. Cambridge University Press, 2007.

8 

Li, Lin, Farshad Amini, Yi Pan, Saiyu Yuan and Boca Cetin. Hydraulics of Levee Overtopping. CRC Press, 2020.

9 

Ludy, Jessica, and G. Matt Kondolf. “Flood risk perception in lands ”protected" by 100-year levees." Natural hazards 61, no. 2 (2012): 829-842.

10 

O’Neill, Karen M. Rivers by Design: State Power and the Origins of U.S. Flood Control. Duke University Press, 2006.

11 

Rosenthal, Sandy. Words Whispered in Water: Why the Levees Broke in Hurricane Katrina. Mango Media, 2020.

See also: Flood Barriers, Movable; Floods and Flooding; Louisiana Coast; New Orleans; Storm Surges.

Citation Types

Type
Format
MLA 9th
M. Cruse, Anna. "Levees." Encyclopedia of Climate Change, Third Edition, edited by Richard M. Renneboog, Salem Press, 2022. Salem Online, online.salempress.com/articleDetails.do?articleName=Climate3_0351.
APA 7th
M. Cruse, A. (2022). Levees. In R. M. Renneboog (Ed.), Encyclopedia of Climate Change, Third Edition. Salem Press. online.salempress.com.
CMOS 17th
M. Cruse, Anna. "Levees." Edited by Richard M. Renneboog. Encyclopedia of Climate Change, Third Edition. Hackensack: Salem Press, 2022. Accessed December 14, 2025. online.salempress.com.