Editing Levee (section)

=== River flood prevention ===
[[File:Sacramento River broken levee.jpg|thumb|Broken levee on the Sacramento River]]
[[File:GretnaLevee.jpg|thumb|A levee keeps high water on the Mississippi River from flooding [[Gretna, Louisiana|Gretna]], [[Louisiana]], in March 2005.]]

Prominent levee systems have been built along the [[Mississippi River]] and [[Sacramento River]] in the [[United States]], and the [[Po River|Po]], [[Rhine]], [[Meuse River]], [[Rhône]], [[Loire]], [[Vistula]], the delta formed by the Rhine, Maas/Meuse and [[Scheldt]] in the [[Netherlands]] and the [[Danube]] in [[Europe]]. During the Chinese [[Warring States period]], the [[Dujiangyan irrigation system]] was built by the [[Qin (state)|Qin]] as a [[water conservation]] and flood control project. The system's infrastructure is located on the [[Min River (Sichuan)|Min River]], which is the longest tributary of the [[Chang Jiang|Yangtze River]], in [[Sichuan]], [[China]].

The Mississippi levee system represents one of the largest such systems found anywhere in the world. It comprises over {{convert|3500|mi|km|order=flip|abbr=on}} of levees extending some {{convert|1000|km|mi|abbr=on}} along the Mississippi, stretching from [[Cape Girardeau, Missouri|Cape Girardeau]], [[Missouri]], to the [[Mississippi River Delta|Mississippi delta]]. They were begun by French settlers in [[Louisiana]] in the 18th century to protect the city of [[New Orleans]].<ref name=Kemp>Kemp, Katherine. [http://www.tulane.edu/~bfleury/envirobio/enviroweb/FloodControl.htm ''The Mississippi Levee System and the Old River Control Structure''The Louisiana Environment.] Tulane.edu</ref> The first Louisiana levees were about {{convert|3|ft|cm|-1|order=flip|abbr=on}} high and covered a distance of about {{convert|50|mi|km|order=flip|abbr=on}} along the riverside.<ref name=Kemp/> The U.S. Army Corps of Engineers, in conjunction with the Mississippi River Commission, extended the levee system beginning in 1882 to cover the riverbanks from [[Cairo, Illinois]] to the mouth of the [[Mississippi River Delta|Mississippi delta]] in Louisiana.<ref name=Kemp/> By the mid-1980s, they had reached their present extent and averaged {{convert|24|ft|m|sp=us|order=flip|abbr=on}} in height; some Mississippi levees are as high as {{convert|50|ft|m|sp=us|order=flip|abbr=on}}. The Mississippi levees also include some of the longest continuous individual levees in the world. One such levee extends southwards from [[Pine Bluff, Arkansas|Pine Bluff]], [[Arkansas]], for a distance of some {{convert|380|mi|km|sp=us|order=flip|abbr=on}}. The scope and scale of the Mississippi levees has often been compared to the [[Great Wall of China]].<ref name="NewYorker1987">{{cite magazine|last=McPhee|first=John|title=The Control of Nature: Atchafalaya|magazine=The New Yorker|date=February 23, 1987|url=http://www.newyorker.com/archive/1987/02/23/1987_02_23_039_TNY_CARDS_000347146|access-date=May 12, 2011|archive-url=https://web.archive.org/web/20110513171926/http://www.newyorker.com/archive/1987/02/23/1987_02_23_039_TNY_CARDS_000347146|archive-date=May 13, 2011|url-status=live}}  Republished in {{cite book | author=McPhee, John | title=The Control of Nature | publisher=Farrar, Straus and Giroux | year=1989 | isbn=0-374-12890-1 | page = 272 }}</ref>

The United States Army Corps of Engineers (USACE) recommends and supports [[cellular confinement]] technology (geocells) as a best management practice.<ref>{{cite web|url=https://apps.dtic.mil/sti/pdfs/ADA354949.pdf|archive-url=https://web.archive.org/web/20130408135145/http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA354949|url-status=live|archive-date=8 April 2013|title= levee rehabilitation in USACE Technical Report REMR-GT-26, Innovative Methods for Levee Rehabilitation|author=Edward B. Perry|date=September 1998|website=Dtic.mil|access-date=3 April 2019}}</ref> Particular attention is given to the matter of surface erosion, [[wave overtopping|overtopping]] prevention and protection of levee crest and downstream slope. Reinforcement with geocells provides tensile force to the soil to better resist instability.

Artificial levees can lead to an elevation of the natural riverbed over time; whether this happens or not and how fast, depends on different factors, one of them being the amount and type of the [[bed load]] of a river. [[Alluvium|Alluvial]] rivers with intense accumulations of sediment tend to this behavior. Examples of rivers where artificial levees led to an elevation of the riverbed, even up to a point where the riverbed is higher than the adjacent ground surface behind the levees, are found for the [[Yellow River]] in China and the [[Mississippi River|Mississippi]] in the United States.