Hold back storm surges with giant air-filled walls
Katrina's wind-driven waves weakened the levees designed to keep Lake Pontchartrain from spilling into the city eight feet below it. Some 58 billion gallons of water-about 3 percent of the lake's volume-flooded more than three quarters of the city.
Since the 1960s, engineers have considered installing floodgates that would close during hurricanes to prevent a storm surge from backing up into the lake. But the concept was scrapped in 1977 because of concerns that the gates would hinder marine life and nutrients from moving back and forth with the tides.
Similar gates already shield Holland and Britain from violent North Sea storms and tidal surges, and are under construction in Venice. Like New Orleans, Venice lies below sea level, inside a slowly sinking lagoon. By 2011, engineers in Venice will have installed an array of 78 steel-and-concrete barriers at three inlets that separate the lagoon from the Adriatic Sea. Together the string of barriers will span nearly a mile, a distance greater than what would be required to separate New Orleans from the Gulf of Mexico. "I think you could build a solution in New Orleans similar to what we are now building in Venice," says Maria Teresa Brotto, the project's managing engineer.
A row of giant sea gates would stretch across each of the two narrow waterways that link Lake Pontchartrain to the Gulf, at Rigolets and Chef Menteur Pass. During fair weather, the hollow gates, which would together span about 3,000 feet, would be filled with water. They would rest flush against the seafloor, where they wouldn't interfere with marine life or tides.
Should a storm approach, compressor pumps would force air into sealed chambers inside the gates, making them buoyant. One side of each hinged gate would be attached to a concrete foundation on the seafloor; the opposite side would rise out of the water.
Alberto Scotti, chief designer of the Venice project, says his sea gates can withstand waves cresting to 16 feet. To fend off a category-5 storm, Louisiana's gates would need to be reinforced to handle winds upward of 160 mph. They would also have to be taller than those in Venice. "We know that Katrina had in some places a 27-foot storm surge," says Susan Jackson, a public affairs officer for the U.S. Army Corps of Engineers New Orleans District.
The hurdle is cost, with estimates ranging from $500 million to more than a billion.
Army Corps engineers are evaluating several concepts. Preliminary hurricane-protection recommendations
are due by early summer.
I like the idea of the floating homes. It is cool but very very expensive. Still it guarantees nothing... It will be like living in boat :)
Jen @ http://www.goldshares.org
It will be like living in a boat only when there is a huge storm. Still I would prefer to watch the storm on the news, not to experience it.
Mira - http://www.whitenteeth.net/
These 5 ideas are all fine, but there is no mention of the obvious best option.
Jack up the houses to above flood level and fill in with hydraulic dredged sand and silt from the Mississippi or other close by fill material.
This could be done a section at a time next to the levees and would strengthen the levees until all of the city is above flood level.
It is the only option that makes sense to me.
I built levees for a living for 35 years and I understand the power of rivers. To think of all of those people living below sea level with ever increasing chance of hurricanes is a little too much of a gamble. The other increasing risk is the Mississippi river where the bottom of the river is higher than the surrounding land. That needs to be changed also. We think nothing of giving billions to support the oil industry which makes the most profit. Some also think that corporate farming needs supports. Why not use these unnecessary funds for something like raising New Orleans. Makes no sense to you? Neither should the above mentioned folly of supporting industries which need no help from taxpayers. N.O. either get up or get out.