A levee, levée (from the feminine past participle of the French verb lever, "to raise"), floodbank or stopbank is a natural or artificial slope or wall, usually earthen and often parallels the course of a river. French Verbs are a complex area of French grammar, with a conjugation scheme that allows for three finite moods (with anywhere from two to five Soil, often typeset as SOiL, is a four piece rock band from Chicago Illinois United States founded by Shaun Glass Tom Schofield Tim King and Adam Zadel "Riverine" redirects here For the use of that term in Maritime geography, see there [1] Linguists agree that the term "levee" came into English use in New Orleans. It is known in Europe as a dike. LeveeEmbankmentDitch A dike (or dyke) levee, levée, embankment, floodbank or stopbank is a natural or artificial
Contents |
Levee Failures and Breaches
Man-made levees can fail in a number of ways. The most frequent (and dangerous) form of levee failure is a breach. A levee breach is when part of the levee actually breaks away, leaving a large opening for water to flood the land protected by the levee. A breach can be a sudden or gradual failure that is caused either by surface erosion or by a subsurface failure of the levee. Levee breaches are often accompanied by boils, or sand boils. A sand boil occurs when the upward pressure of water flowing through soil pores under the levee (underseepage) exceeds the downward pressure from the weight of the soil above it. The underseepage resurfaces on the landside, in the form of a volcano-like cone of sand. Boils signal a condition of incipient instability which may lead to erosion of the levee toe or foundation or result in sinking of the levee into the liquefied foundation below. Complete breach of the levee may quickly follow.
Sometimes levees are said to fail when water overtops the crest of the levee. Levee overtopping can be caused when flood waters simply exceed the lowest crest of the levee system or if high winds begin to generate significant swells in the ocean or river water to bring waves crashing over the levee. Overtopping can lead to significant landside erosion of the levee or even be the mechanism for complete breach. Properly built levees are armored or reinforced with rocks or concrete to prevent erosion and failure.
In New Orleans
The words levee and levee breach were brought heavily into the public consciousness after the levee failures in metro New Orleans on 29 August, 2005 when Hurricane Katrina passed east of the city. Events 708 - Copper coins are minted in Japan for the first time (Traditional Japanese date: August 10, 708) Levees breached in over 50 different places submerging eighty percent (80%) of the city. Most levees failed due to water overtopping them but some failed when water passed underneath the levee foundations causing the levee wall to shift and resulting in catastrophic sudden breaching. The sudden breaching released highly pressured water that moved houses off their foundations and tossed cars into trees. This happened in the Ninth Ward when the Industrial Canal breached and also in the Lakeview neighborhood when the 17th Street Canal breached. The Industrial Canal is a 55 mile (9 km Waterway in New Orleans Louisiana, United States. Effects of breached levees are discussed further in and 2005 levee failures in Greater New Orleans, which cites a death toll of 1,464. In late August 2005 there were over 50 failures of the Levees and flood walls protecting New Orleans Louisiana, and nearby St In New Orleans, the US Army Corps of Engineers is, by federal mandate, the sole agency responsible for levee design and construction as defined in the Flood Control Act of 1965. The United States Army Corps of Engineers ( USACE) is a federal agency and a major Army command made up of some 34600 Civilian and 650 Military personnel The Flood Control Act of 1965, Title II of, was enacted on October 27 1965 by the 89th Congress and authorized the U
Other breaches
The Great Mississippi Flood occurred in 1927 when the Mississippi River breached levees and flooded 27,000 square miles (70,000 km²), killing 246 people in seven states and displacing 700,000 people. This article is about the Great Mississippi Flood of 1927 For the Mississippi Flood of 1993 see Great Flood of 1993. The Mississippi River is the second longest River in the United States, with a length of from its source in Lake Itasca in Minnesota to
In the North Sea flood of 1953, levees and flood defenses collapsed in the United Kingdom and the Netherlands, killing over 2,100 people. The North Sea flood of 1953 and the associated storm combined to create a major Natural disaster which affected the coastlines of the Netherlands and England The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located The Netherlands ( Dutch:, ˈnedərlɑnt is the European part of the Kingdom of the Netherlands, which consists of the Netherlands the Netherlands
On 3 June, 2004, Jones Tract, an inland island that is protected by a series of levees located in the Sacramento-San Joaquin Delta, failed. Events 350 - Roman usurper Nepotianus, of the Constantinian dynasty, proclaims himself Roman Emperor, entering The Sacramento-San Joaquin River Delta is an expansive inland River delta and Estuary in northern California in the United States. Though the exact cause of the levee failure is not known, the breach in the levee allowed water from the Middle River to flood the island. An island (ˈaɪlənd or isle (/ˈaɪl/ is any piece of land that is completely surrounded by water in two dimensions above high tide and isolated from other significant
On January 5, 2008, a levee in Fernley, Nevada burst, flooding portions of the town and forcing the evacuations of 3,500 residents. Events 1477 - Battle of Nancy: Charles the Bold is killed and Burgundy becomes part of France. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Fernley is a city in Lyon and Washoe counties in the US state of Nevada. Fernley is a city in Lyon and Washoe counties in the US state of Nevada.
Artificial levees
The main purpose of an artificial levee is to prevent flooding of the adjoining countryside; however, they also confine the flow of the river resulting in higher and faster water flow. A flood is an overflow of an expanse of water that submerges land a deluge Rural areas can be large and isolated (also referred to as "the country" and/or "the countryside over the course of time "Riverine" redirects here For the use of that term in Maritime geography, see there Water is a common Chemical substance that is essential for the survival of all known forms of Life.
Levees are usually built by piling earth on a cleared, level surface. Broad at the base, they taper to a level top, where temporary embankments or sandbags can be placed. A sandbag (floodbag is a sack made of burlap, polypropylene or other materials that is filled with Sand or Soil and used for such purposes as flood Because flood discharge intensity increases in levees on both river banks, and because silt deposits raise the level of riverbeds, planning and auxiliary measures are vital. A stream bed is the channel bottom of a Stream or River or creek the physical confine of the normal water flow Silt is Soil or rock derived Granular material of a Grain size between sand and clay Sections are often set back from the river to form a wider channel, and flood valley basins are divided by multiple levees to prevent a single breach from flooding a large area.
Artificial levees require substantial engineering. Their surface must be protected from erosion, so they are planted with vegetation such as Bermuda grass in order to bind the earth together. Not to be confused with the vertebrate clade " Cynodont " Cynodon ( Greek "Dog-tooth" is a genus of nine species of On the land side of high levees, a low terrace of earth known as a banquette is usually added as another anti-erosion measure. On the river side, erosion from strong waves or currents presents an even greater threat to the integrity of the levee. The effects of erosion are countered by planting with willows, weighted matting or concrete revetments. Willows, sallows and osiers form the Genus Salix, around 400 species of Deciduous Trees and Shrubs found primarily Revetments, or revêtements (following the original French spelling are structures placed on banks or cliffs in such a way as to absorb the energy of incoming water Separate ditches or drainage tiles are constructed to ensure that the foundation does not become waterlogged.
The first levees were constructed over 3,000 years ago in ancient Egypt, where a system of levees was built along the left bank of the River Nile for more than 600 miles (966 km), stretching from modern Aswan to the Nile Delta on the shores of the Mediterranean. Ancient Egypt was an Ancient Civilization in eastern North Africa, concentrated along the lower reaches of the Nile River in what is now The Nile (النيل, Ancient Egyptian iteru or Ḥ'pī, Coptic piaro or phiaro) is a major north-flowing River Aswan (formerly spelled Assuan (in standard أسوان Aswān) Egyptian: Swenet ( trade) Coptic: Swān; Greek The Nile Delta ( Arabic: دلتا النيل) is the delta formed in Northern Egypt ( Lower Egypt) where the Nile River spreads The Mesopotamian civilizations and ancient China also built large levee systems. Mesopotamia (from the Greek meaning "land between the rivers" is an area geographically located between the Tigris and Euphrates rivers largely corresponding Chinese civilization originated in various city-states along the Yellow River ( valley in the Neolithic era Because a levee is only as strong as its weakest point, the height and standards of construction have to be consistent along its length. Some authorities have argued that this requires a strong governing authority to guide the work, and may have been a catalyst for the development of systems of governance in early civilizations. However others point to evidence of large scale water-control earthen works such as canals and/or levees dating from before King Scorpion in Predynastic Egypt during which governance was far less centralized. The Predynastic Period of Egypt (prior to 3100 BC is traditionally the period between the Early Neolithic and the beginning of the Pharaonic monarchy beginning with King
In modern times, prominent levee systems exist along the Mississippi River and Sacramento Rivers in the United States, and the Po, Rhine, Meuse River, Loire, Vistula, the river delta in the Netherlands and Danube in Europe. The Mississippi River is the second longest River in the United States, with a length of from its source in Lake Itasca in Minnesota to The Sacramento River is the longest River entirely within the U The United States of America —commonly referred to as the The Po ( Latin: Padus, Po Ligurian: Bo, Greek: Eridanus) is a river that flows 652 km(405 miles (682 km by considering The Rhine (Rhein Rijn Rhin Reno Rain Rhenus is one of the longest and most important Rivers in Europe at 1320 kilometres (820 mi with an average discharge The Meuse (in Dutch and in German: "Maas" in Latin: "Mosa" in Celtic:"Mus" (the rootword presumingly Loire ( Arpitan: Lêre, Occitan: Léger) is an administrative department in the east-central part of France occupying the The Netherlands ( Dutch:, ˈnedərlɑnt is the European part of the Kingdom of the Netherlands, which consists of the Netherlands the Netherlands The Danube (In Donau from earlier Danuvius, Celtic *dānu, meaning "to flow run" Slovak and Polish Dunaj
The Mississippi River levee system represents one of the largest such systems found anywhere in the world. They comprise over 3,500 miles (5,600 km) of levees extending some 1,000 miles (1,600 km) along the Mississippi, stretching from Cape Girardeau, Missouri to the Mississippi Delta. The Mississippi Delta is the distinct northwest section of the state of Mississippi that lies between the Mississippi and Yazoo Rivers Technically They were begun by French settlers in Louisiana in the 18th century to protect the city of New Orleans. The State of Louisiana ( or, État de Louisiane, pronounced) is a state located in the southern region of the United States of America New Orleans (nʲuːˈɔrliənz nʲuːˈɔrlənz French: La Nouvelle-Orléans) is a major United States port city and the largest city in Louisiana The first Louisianan levees were about 3 feet (0. 9 m) high and covered a distance of about 50 miles (80 km) along the riverside. By the mid-1980s, they had reached their present extent and averaged 24 feet (7 m) in height; some Mississippi levees are as much as 50 feet (15 m) high. The Mississippi levees also include some of the longest continuous individual levees in the world. One such levee extends southwards from Pine Bluff, Arkansas for a distance of some 380 miles (611 km). Pine Bluff is the largest city and County seat of Jefferson County, Arkansas, United States.
Natural levees
Levees are commonly thought of as man-made, but they can also be natural. The ability of a river to carry sediments varies very strongly with its speed. When a river floods over its banks, the water spreads out, slows down, and deposits its load of sediment. Over time, the river's banks are built up above the level of the rest of the floodplain. ||-||-||-||-||-||-||-||}A floodplain, or flood plain, is flat or nearly flat land adjacent to a Stream or River that experiences occasional or periodic The resulting ridges are called natural levees.
When the river is not in flood state it may deposit material within its channel, raising its level. The combination can raise not just the surface, but even the bottom of the river above the surrounding country. Natural levees are especially noted on the Yellow River in China near the sea where oceangoing ships appear to sail high above the plain on the elevated river. The Yellow River or Huang He / Hwang Ho ( Hatan Gol Queen river) is the second-longest river in China (after the Yangtze River) and the China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National Natural levees are a common feature of all meandering rivers in the world.
Levees in tidal waters
The basic process occurs in tidal creeks when the incoming tide carries mineral material of all grades up to the limit imposed by the energy of the flow. As the tide overflows the sides of the creek towards high water, the flow rate at the brink slows and larger sediment is deposited, forming the levee. At the height of the tide, the water stands on the salt-marsh or flats and the finer particles slowly settle, forming clay. In the early ebb, the water level in the creek falls leaving the broad expanse of water standing on the marsh at a higher level.
The area of water on the marsh is much greater than the water surface of the creek so that in the latter, the flow rate is much greater. It is this rush of water, perhaps an hour after high water, which keeps the creek channel open. The cross-sectional area of the water body in the creek is small compared with that initially over the levee which at this stage is acting as a weir. The deposited sediment (coarse on the levee and on the mud flats or salt-marsh) therefore tends to stay put so that, tide by tide, the marsh and levee grow higher until they are of such a height that few tides overflow them. In an active system, the levee is always higher than the marsh. That is how it came to be called "une rive levée", or raised shore.
References
- ^ Henry Petroski (2006), Levees and Other Raised Ground, vol. 94, American Scientist, pp. pp. 7-11
See also
External links
- Levees.Org (activist group in New Orleans to Hold the Corps Accountable)
- New Orleans and the Delta
- DeltaWorks.Org Project of levees, dams and barriers in the Netherlands
- Effort to rebuild New Orleans Levees to Category 5 Design (non-profit)
- (Activists Blocked New Orleans Levee Plan)
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic