The fixes are not cheap ...
They Saw It Coming - New York Times
September 2, 2005
By MARK FISCHETTI
... (I wrote an article for Scientific American in 2001 that described the very situation that was unfolding) but because I knew that a large-scale engineering plan called Coast 2050 - developed in 1998 by scientists, Army engineers, metropolitan planners and Louisiana officials - might have helped save the city, but had gone unrealized.
The debate over New Orleans's vulnerability to hurricanes has raged for a century. By the late 1990's, scientists at Louisiana State University and the University of New Orleans had perfected computer models showing exactly how a sea surge would overwhelm the levee system, and had recommended a set of solutions. The Army Corps of Engineers, which built the levees, had proposed different projects.
... Fed up with the splintered efforts, Len Bahr, then the head of the Louisiana Governor's Office of Coastal Activities, somehow dragged all the parties to one table in 1998 and got them to agree on a coordinated solution: Coast 2050. Completing every recommended project over a decade or more would have cost an estimated $14 billion, so Louisiana turned to the federal government. While this may seem an astronomical sum, it isn't in terms of large public works; in 2000 Congress began a $7 billion engineering program to refresh the dying Florida Everglades. But Congress had other priorities, Louisiana politicians had other priorities, and the magic moment of consensus was lost...
... Cut several channels in the levees on the Mississippi River's southern bank (the side that doesn't abut the city) and secure them with powerful floodgates that could be opened at certain times of the year to allow sediment and freshwater to flow down into the delta, re-establishing it.
Build a new navigation channel from the Gulf into the Mississippi, about 40 miles south of New Orleans, so ships don't have to enter the river at its three southernmost tips 30 miles further away. For decades the corps has dredged shipping channels along those final miles to keep them navigable, creating underwater chutes that propel river sediment out into the deep ocean. The dredging could then be stopped, the river mouth would fill in naturally, and sediment would again spill to the barrier islands, lengthening and widening them. Some planners also propose a modern port at the new access point that would replace those along the river that are too shallow to handle the huge new ships now being built worldwide.
Erect huge seagates across the pair of narrow straits that connect the eastern edge of Lake Pontchartrain, which lies north of the city, to the gulf. Now, any hurricane that blows in from the south will push a wall of water through these straits into the huge lake, which in turn will threaten to overflow into the city. That is what has filled the bowl that is New Orleans this week. But seagates at the straits can stop the wall of water from flowing in. The Netherlands has built similar gates to hold back the turbulent North Sea and they work splendidly.
Finally, and most obviously, raise, extend and strengthen the city's existing but aging levees, canal walls and pumping systems that worked so poorly in recent days.