Levees and Flood Control Devices

[diablo234]

Since many coastal cities are at risk for flooding I thought I would create a thread here for this topic to showcase each cities different mechanisms for flood control.

Anyways after Hurricane Katrina, the Army Corp of Engineers along with the local government have built and rebuilt levees and storm surge bariers in and around New Orleans.

Here are some storm surge barriers in Louisiana which are being built to protect New Orleans from future storm surge.


Inner Harbor Storm Surge Barrier


Seabrook Floodgate

In addition New Orleans also has several mechanisms in place for flooding along the Mississippi.


The Morganza Floodway being used to divert floodway from the Mississippi River to the less populated Atchafalaya Basin.


The Old River Control Structure 50 miles (80 km) northwest of Baton Rouge and 118 miles (190 km) northwest of New Orleans, which has a dual purpose of both diverting floodwater away from New Orleans and preventing the Mississippi from shifting it's course. The water being diverted here also heads into the Atchafalaya Basin.


The Bonnet Carre Spillway is the last line of defense against flooding from the Mississippi and is used to channel excess floodwater to Lake Pontchartrain.


An example of a levee on the Mississippi RIver in Gretna, Louisiana just outside of New Orleans.

[diablo234]

Footage of the Morganza Floodway being opened because of recent flooding along the Mississippi.

[Suburbanist]

The Dutch have, arguably, the most advanced and comprehensive flood control system in the World. Much of the country were built over former marshland, which used to flood twice a day and naturally sink over the centuries as it dries out.

Main flood control structures are canals, pumps and levees. I'll come with some pictures of them later. God knows how many km of levees (dykes) that keep water out of the polders.

From 1955-1997 the Dutch completed the Delta Works, a set of flood control projects to keep the country safe. Some of its most impressive structures are dams and gates, unlike levees, let water in under normal condition but keep water out if there is a storm surge on the North Sea.

The most famous of those is the Maeslantkering, in Rotterdam. As it is the 2nd busiest port on Earth (ok, there are discussions about how to measure traffic on a port), they needed a movable system to allow navigation under normal conditions but keep it out should a storm surge form in the sea. So they came with these massive gates that close in a double-semi-arch pattern.

Each gate has something like 190m in extension.

I took these pics in January when I visited the site:

[DarkLoki]

In the Netherlands we have about 3585 kilometres of primary flood defences. Another famous one is these defences is the 30km long Afsluitdijk.



A big part of flood defences in the Netherlands are actually natural, the dunes. Dutch engineers are participating in waterworks all over the world. At the moment they are for instance active in Bangladesh and I believe they are also involved in the new barriers around New Orleans.

[diablo234]

The Thames Barrier just outside of London.

[diablo234]

Originally Posted by DarkLoki

I believe they are also involved in the new barriers around New Orleans.

Actually you are correct, since many of the concepts used in rebuilding the levees in New Orleans and adding the storm surge gates came from the Netherlands and many Dutch engineers were brought over for overseeing the construction.

[diablo234]

The River Walk in San Antonio was actually built with flood control in mind after a disastorous flood in 1921. Instead of building over the river they decided to make it a public space and added several locks as well in addition to several channels in case the water level gets to be too high. Now it has become a tourist attraction in it's own right.







image hosted on flickr

[DarkLoki]

A cool picture of the dike between the "Markermeer" and the "Flevopolder". Both of these area's were once part of the inland sea "Zuiderzee".

[desertpunk]

Desert cities have flood control structures too:

Albuquerque Metropolitan Flood Control Authority (AMAFCA)

North Diversion Channel
A massive concrete lined channel that feeds flash flood waters from arroyos and smaller channels into the Rio Grande River.

[Suburbanist]

Which of big Southwestern desert cities is more prone to flash floods and runoffs (rain in the desert, AFAIK, is usually a very dangerous business): Tucson, Albuquerque or Phoenix?

[diablo234]

Originally Posted by Suburbanist

Which of big Southwestern desert cities is more prone to flash floods and runoffs (rain in the desert, AFAIK, is usually a very dangerous business): Tucson, Albuquerque or Phoenix?

Probably either Tucson or Phoenix because of the monsoon season in the summer as moisture from the Gulf of California heads inland and occasionally causes flash floods. However El Paso and Albuquerque can also be affected by storms and most recently Hurricane Dolly has caused flooding in parts of El Paso.

[desertpunk]

Originally Posted by Suburbanist

Which of big Southwestern desert cities is more prone to flash floods and runoffs (rain in the desert, AFAIK, is usually a very dangerous business): Tucson, Albuquerque or Phoenix?

All southwestern cities are prone to flash flooding. El Paso and Albuquerque have additional challenges due to the relatively steeper slopes they're built on. Flash floods in Las Vegas and Tucson have been especially deadly as once clear roads become raging torrents of water. Phoenix is fairly flat and has excellent infrastructure so it deals with flash flooding very well.

[diablo234]

Also known as the St. Petersburg Dam this structure was just recently completed and protects the city of St. Petersburg in Russia from the Gulf of Finland.

[diablo234]

A floodgate in Cairo, Illinois which protects the city from flooding against the Mississippi and Ohio Rivers.

[diablo234]

The Red River Floodway protects the city of Winnipeg, Manitoba in Canada from flooding on the Red River. It is 47 km (29 miles) long and can carry floodwater at a rate of up to 2,550 cubic metres (91,700 cubic feet) per second. It was built partly in response to the disastrous 1950 Red River flood which devastated the city. The success of this project has caused the cities of Grand Forks and Fargo in the US state of North Dakota to consider building similar floodways after the the devastating floods of 1997 and 2009.

[thun]

Vienna has the 21km long "Neue Donau" parallel to the Danube river for flood protection and recreational purposes:

Inlet:


The area between the "two Danubes" is called Donauinsel (Danube Island), a mayor park of the city:


New Danube in front, Old Danube in the back:

[diablo234]

is a water control structure on the Assiniboine River in Portage la Prairie, Manitoba, Canada and was made as part of a larger attempt to prevent flooding in the Red River Valley. The Portage Diversion consists of two separate gates which divert some of the flow of water in the Assiniboine River to a 29 km (18 miles)long diversion channel that empties into Lake Manitoba near Delta Beach. This helps prevent flooding on the Assinboine down river from the diversion, including in Winnipeg, where the Assiniboine River meets the Red River.

[diablo234]

The Gulf Intracoastal Waterway West Closure Complex just outside of New Orleans will consist of a navigable floodgate, a pumping station, floodwalls, sluice gates, foreshore protection, and an earthen levee. The complex was designed to reduce risk for residences and businesses in the project area from a storm surge associated with a tropical event with an intensity that has a 1 percent chance of occurring in any given year. This project is scheduled to be hurricane ready by June 1, 2011, and completely finished in late 2012.

[DarkLoki]

A cool flood control device in the Netherlands is the "plofsluis" or "pop lock". Part of the Dutch defence was to inundate lands to slow down the enemy. A new canal punctured a hole in one of these defences. To make sure water would not flow away trough the canal this pop lock was build. The concept is that when needed the supports of the lock explode, dropping tons of gravel and sand in the canal thereby closing of the canal in a single explosion.

[woutero]

As mentioned, The Netherlands has an extensive system of dams, dikes, levees, draining canals and pumps. In fact, about 2/3 of land in The Netherlands can only exists because water is actively pumped out. This means that if this were not done, the land would flood. Only about 1/3 of the country has natural water runoff (water that flows down into rivers, and into the sea). So in 2/3 of the country water has to be pumped up in order to reach the sea.

This system is managed by a separate government layer (not part of the local, provincial or national governments, with their own elections - although some larger waters are managed by the national government). These water boards date as far back as the 1100s and were the first democratic institutions in The Netherlands. It is often said it is at the basis of The Netherlands' natural instinct to search for common ground and co-operation.

Maps below are taken from the National Water Plan. To get a feeling of scale: from bottom left to top right is about 330 km.

This first one shows the 'Dijkringen' (Dike Rings), and the chance of an outer dike failing. Within these rings, water is managed, and pumped out into the sea or into the main rivers. The land next to the river is usually lower than the river itself. Only the really light colored areas have natural water runoff:


This map shows estimated water depth in case of flooding:


In recent decades the attitude toward water has shifted from 'trying to keep the water out' to 'learning to live with water'. Before, the goal was often to increase the speed of rainwater and river water runoff, by straightening out streams and rivers, and increasing pump capacity. This has lead to an increase in peak water runoff, which is hard to manage. So nowadays the focus is on slowing water down and on local water retention and infiltration.