for National Geographic News
A year after Hurricane Katrina hammered the U.S. Gulf Coast and spurred massive flooding in New Orleans, the ecological impacts are still being felt throughout the region.
In particular, human-driven coastal erosion and saltwater intrusionissues that have long been damaging the region's natural storm bufferswere made worse by the powerful hurricane.
The flooding in New Orleans that began on August 30, 2005, "was really an unnatural disaster," said John Day, a distinguished professor emeritus at the Louisiana State University (LSU) School of the Coast and Environment in Baton Rouge.
"We spent the last century doing almost everything we could to destroy our coast in all sorts of waysputting levees on the Mississippi River, slicing thousands of kilometers of canals, massive oil and gas production."
For example, Day says, the canals that connect the city to the coast allow storm surges to travel inland, bringing salt water that damages the land.
One such canal, known as the Mississippi River Gulf Outlet, was built in the mid-1960s to be a 76-mile (122-kilometer) shortcut between the Gulf of Mexico and New Orleans.
Hailed as an engineering marvel at the time, the canal is rarely used today.
Before the record hurricane season of 2005, salt water brought inland by the canal was fingered as the culprit in the death of thousands of acres of cypress swamp, a natural buffer against storms.
And when Katrina hit, levee failures on the canal allowed water to pour into St. Bernard Parish and New Orleans East (read "New Orleans Flooded in Wake of Hurricane Katrina" [August 2005]).
"Had those cypress swamps been in place, the levees probably wouldn't have failed," Day said.
The continuing effects of saltwater intrusion driven by Katrina and Hurricane Ritawhich hit the Gulf Coast about a month latercan be still seen in the wilting trees and plants far from the coast.
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