Drainage in New Orleans

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Elevation map of New Orleans. Blue/purple indicates elevations below the average level of LakePontchartrain (1983-2001) and orange/brown indicates elevations above.

Vertical cross-section of New Orleans, showing maximum levee height of 23Â feet

Drainage in New Orleans, Louisiana has been a major concern since the founding of the city in the

early 18th century, remaining an important factor in the history of New Orleans today. The centralportion of metropolitan New Orleans (New Orleans/Metairie/Kenner) is fairly unique in that it isalmost completely surrounded by water: Lake Pontchartrain to the north, Lake Borgne to the east,wetlands to the east and west, and the Mississippi River to the south. Much of the land area betweenthese bodies of water is at or below sea level, and no longer has a natural outlet for flowing surfacewater. As such, virtually all rainfall occurring within this area must be removed through eitherevapotranspiration or pumping. Thus, flood threats to metropolitan New Orleans include theMississippi River, Lake Pontchartrain, and natural rainfall. Artificial levees have been built to keepout rising river and lake waters but have had the negative effect of keeping rainfall in.

Contents

1 History

2 Hurricane Katrina

2.1 After Katrina

3 See also

4 References

5 External links

History

New Orleans was originally built on natural levees along the Mississippi River that were a result ofsoil deposits left from the river's annual floods. The site chosen for New Orleans had manyadvantages. Because it sits where distance between the river and Lake Pontchartrain is shortest,Louisiana Indians had long used the area as a depot and market for goods carried between the twowaterways. The narrow strip of land also aided rapid troop movements, and the river's crescentshape slowed ships approaching from downriver and exposed them to gunfire,[1] however floodingwas always a hazard.

The first artificial levees and canals were built in early colonial times. They were erected to protectNew Orleans against routine flooding from the Mississippi River. The "back of town" away from theriver originally drained down into the swamps running toward Lake Pontchartrain. Flooding fromthe lake side was rare and less severe as most of the old town had been built on high ground alongthe riverfront.

As the city grew, demand for more land encouraged expansion into lower areas more prone toperiodic flooding. For most of the 19th century most residential buildings were raised up at least afoot above street level (often several feet), since periodic flooding of the streets was a certainty atthe time.

In the 1830s state engineer George T. Dunbar proposed an ambitious system of undergrounddrainage canals beneath the streets. The goal was to drain water by gravity into the low lyingswamps, supplementing this with canals and mechanical pumps. The first of the city's steam enginepowered drainage pumps, adapted from a ship's paddle wheel and used to push water along theOrleans Canal out to Bayou St. John, was constructed in this decade. However, only a few ofDunbar's plans were actually implemented as the panic of 1837 largely ended major systematic

improvements for a generation.

In 1859 surveyor Louis H. Pilié improved the drainage canals, bricking in some portions. Fourlarge steam "draining machines" were built to push water through the canals into the lake.

In 1871, some 36 miles (58Â km) of canals were built in the city for both improved drainage andsmall vessel shipping within town. However, despite earlier efforts, at the end of the 19th century itwas still common for water to cover streets from curb to curb after rainstorms, sometimes for days.

In 1893, the city government formed the Drainage Advisory Board to come up with better solutionsto the city's drainage problems. Extensive topographical maps were made and some of the nation'stop engineers were consulted. In 1899, a bond was floated, and a 2 mill per dollar property taxapproved, which funded and founded the Sewerage & Water Board of New Orleans. The Sewerage &Water Board had the responsibility of draining the city along with constructing a modern sewageand tap water system for the city, which, at the time, still relied heavily on cisterns and outhouses.(A different entity, the Orleans Levee Board, is in charge of supervision of the city's levee andfloodwall system.)

The Sewerage & Water Board found A. Baldwin Wood, a young engineer who not only supervised theplans for improved drainage and pumping, but also invented a number of improvements in pumpsand plumbing in the process. These improvements were not only used in New Orleans, but adoptedall over the world.

The central power plant for the pumping stations of the New Orleans drainage system, 1904

As the 20th century progressed, much of the land that had previously been swampland or consideredfit for no other use than cow pasture (due to periodic flooding), was drained. The city then expandedback from the natural higher ground close to the river and the natural bayou formed ridges.

On 15 April 1927 in what became known as the Great Mississippi Flood of 1927, the city wasdeluged by a downpour of some 15 inches (380Â mm) of rain within 19 hours. At the time, almost allof the city's pumps relied completely on the municipal electricity system, which went out early in thestorm, thus knocking the pumps off line, which led to extensive flooding in the city. After this, backup diesel generators with sufficient fuel to run the pumps for at least a day if electricity failed wereadded to the pumping stations. The "Good Friday Flood", as it was known locally, happened whenthe Mississippi River levels were dangerously high along the levees at the city, but was not directlyconnected to the more wide-ranging flood.

1927 also saw the start of a project to build a more extensive system of levees on the shoreline ofLake Pontchartrain. After 1945, all land up to the lake had been developed.

The city's system was effective when the 1947 Fort Lauderdale Hurricane directly hit the city.Wood's drainage pumps kept the city proper mostly dry, while the neighboring suburbs on the EastBank of Jefferson Parish (which at the time did not have a comparable system operational), floodedunder up to 6 feet (1.8Â m) of water.

Most of the city weathered Hurricane Betsy in 1965 without severe flooding, with the majorexception of the Lower Ninth Ward neighborhood. The Lower Ninth Ward is separated from the restof the city by the Industrial Canal and Gulf Intracoastal Waterway. It was flooded not by rainfall, butby a breach in the Industrial Canal levee, resulting in catastrophic flooding and loss of life in theneighborhood.

By the 1980s, the city boasted a system of 20 pumping stations with 89 pumps, with a combinedcapacity of 15,642,000 US gallons (59,210,000Â L) per minute, equal to the flow of the Ohio River.

In May 1995, torrential rains (up to 20 inches (510Â mm) in 12 hours in some places) overwhelmedpumping capacity, flooding substantial portions of the city. Slab houses in some low areas wereflooded, and great numbers of automobiles on the city's flooded streets were declared insurancewrite-offs. This prompted projects increasing drainage capacity in the worst hit areas.

By early 2005, the city had 148 drainage pumps.

Hurricane Katrina

Main article: Hurricane Katrina

The greatest catastrophe in the city's drainage history occurred at the end of August 2005 when itwas hit by Hurricane Katrina, after which eighty percent of the city flooded. Katrina brought tropicalstorm conditions to the city starting the night of 28 August, with hurricane conditions beginning thefollowing day and lasting through the afternoon.

The hurricane itself did not flood the city. Rather, a series of failures in mis-designed levees andfloodwalls allowed water from the Gulf of Mexico and Lake Pontchartrain to flow into the city.

The Industrial Canal was overwhelmed when storm surge, funneled in by the Mississippi River GulfOutlet, overflowed and breached levees and floodwalls in several locations, flooding not only theLower Ninth Ward, but also Eastern New Orleans and portions of the Upper Ninth Ward west of theCanal.

Meanwhile, waters from storm-swollen Lake Pontchartrain poured into the city, first from a breachin the 17th Street Canal, and then from a pair of breaches in both sides of the London Avenue Canal.These canals were among those used to channel water pumped from city streets into the lake. Thestorm caused the flow to reverse, and as water levels rose the entire drainage system failed.Examinations afterwards showed that water levels in these locations never topped the floodwalls,but instead the levees failed with a water level supposedly within their safe tolerance.

In much of town west of the Industrial Canal, residents who did not evacuate before the stormreported that after the storm they were relieved to see their streets dry and the precipitation fromthe storm successfully pumped out. However, disaster was already spreading from the series of

levee breaches. In areas of town far from the breaches, flood water came not in through the streets,but up from the storm drains beneath the street, in some places changing streets from dry to under3 feet (0.91Â m) of water within half an hour.

Flood lines show levels of high water on this Mid City New Orleans house

By the evening of August 30, some 80% of the city was under water. (This figure includes areas ofwidely differing flood levels, ranging from areas where streets were covered with water which neverrose into homes to areas where homes were entirely submerged over the rooftops.) Most of the city'spumping stations were submerged. The few above the water line had no power and the emergencydiesel fuel had run out. These few were often tiny islands in the flood, inaccessible even if intactenough to hypothetically be turned back on.

For most of the city to the west of the Industrial Canal, the flood levels were much the same as thosereached in mid-19th century storms when, like Katrina, major hurricanes created a "lake flood" bypushing Lake Pontchartrain up into the South Shore. At the time of these earlier storms the lowerlying areas of the city had little development, so effects on life and property were much less severe.

West of the Industrial Canal, the parts of the city unflooded or minimally flooded largelycorresponded with areas of the city developed on naturally higher ground before 1900.

On August 31, flood levels started to subside. The water level in the city had reached that of LakePontchartrain, and as the lake started to drain back into the Gulf, some water in the city started toflow into the lake via the same levee breeches they had entered through. In 19th century lake floods,the water soon flowed back into the lake as there were no levees on that side. In 2005, while thelevees proved inadequate to keep the lake out of the city, even in breached form they were sufficientto keep much of the flooding from flowing back out. As breaches were gradually filled, some citypumps were reactivated, supplemented by additional pumps brought in by the United States ArmyCorps of Engineers. Some of the city's pumps which survived could not be reactivated because of thefailures of the canals that they pumped flood waters into. The combined task of closing breaches andpumping the flood waters out took weeks and was compounded by a setback in late September dueto further flooding from Hurricane Rita.

After Katrina

Main article: 2005 levee failures in Greater New Orleans

See also: Civil engineering and infrastructure repair in New Orleans after Hurricane Katrina

By the start of October 2005, only a few small areas of flood waters remained within the city, but thedisastrous flooding in the aftermath of Katrina left the majority of the city's houses and businessesso damaged as to be unusable until major renovations or repairs could be made. An article in theNew Orleans Times-Picayune on 30 November 2005 reported that studies showed the 17th StreetCanal levee was "destined to fail" as a result of fundamental design mistakes by the United StatesArmy Corps of Engineers.[2]

Additional investigations have found more problems with the design and construction of the LondonAvenue Canal, Industrial Canal, MRGO, and other levees and flood walls.

While the majority of the city's drainage pumps were able to be reactivated after the storm, some ofthe usually reliable pumps failed in 2006 due to corrosion. This was caused by wiring beingsubmerged in the brackish water from Katrina.

As a stop-gap measure, the Corps of Engineers installed flood gates at the mouths of the drainagecanals at Lake Pontchartrain, to be closed if the lake water level rises. While this prevents lakewaters from flowing into the vulnerable canals, it also severely limits the ability of the city to pumpout rain water while the gates are closed.

In March 2006, it was revealed that temporary pumps installed by the USACE were defective.[3][4]Until all problems are rectified, concerns remain that parts of the city could experience significantflooding in a storm much smaller than Katrina. The system did survive during Hurricane Gustav in2008. The storm weakened and brought less wind and rain than forecast. "The Lakefront pumpsoperated smoothly".[5]

Metarie Pumping Station, also known as Pumping Station 6, building, constructed in 1899, nearMetarie Road and the head of the 17th Street Canal. Now housing 15 Wood Screw Pumps, it canmove over 6Â billion US gallons (23,000,000Â m3) of water a day.

See also

1947 Fort Lauderdale Hurricane

Bonnet Carré Crevasse

Bonnet Carré Spillway

Effect of Hurricane Katrina on New Orleans

Floods in the United States: 1901-2000

Floods in the United States: 2001-present

Grand Isle Hurricane of 1909

Great Mississippi Flood of 1927

Hurricane Betsy

Hurricane Katrina

Hurricane Rita

Levee failures in Greater New Orleans, 2005

May 8th 1995 Louisiana Flood

New Orleans Hurricane of 1915

Orleans Levee Board

Sauvé's Crevasse

Southeast Louisiana Urban Flood Control Project

References

Notes

^ "The Cabildo - Colonial Louisiana". Louisiana State Museum. Retrieved 11 August 2010.

^ "?".

^ "?". Retrieved 11 August 2010.

^ "?". Retrieved 11 August 2010.

^ "?". Retrieved 11 August 2010.

Bibliography

"Charting Louisiana" Edited by Alfred E. Lemmon, John T. Magill, and Jason R. Wiese; John R.Hebert, consulting editor. Historic New Orleans Collection, 2003

"Geographies of New Orleans" by Richard Campanella, Center for Louisiana Studies, 2006

"History of New Orleans" by John Kendall. Lewis Publishing Company, 1922

"New Orleans The Making of an Urban Landscape" by Peirce F. Lewis. Second Edition, Center forAmerican Places, 2003

"Time and Place in New Orleans" by Richard Campanella. Pelican Publishing Company, 2002

"Transforming New Orleans and Its Environs" edited by Craig E. Colten. University of PittsburghPress, 2000.

"An Unnatural Metropolis: Wresting New Orleans From Nature" by Craig E. Colten, Louisiana StateUniversity Press, Baton Rouge, 2005

"Topical and Drainage Map of New Orleans and Surroundings From Recent Surveys andInvestigations, by T. S. Hardee, Civil Engineer. Thomas Sydenham Hardee, 1878

External links

Wikimedia Commons has media related to Drainage in New Orleans.

New Orleans: The Story of Three Great Public Utilities, 1914

History of New Orleans Drainage, 1718-1893 PDF

The Wood Screw Pump: A Study of the Drainage Development of New Orleans

New Orleans: A Wonderful Drainage System. Colliers Weekly, 1901

New Orleans Hurricane Risk

Public Health and Hurricanes: New Orleans Pilot Project

"Fix The Pumps" blog detailing post-Katrina repairs

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