UI professor helps complete coastline study of Louisiana

BOISE – New Orleans wouldn’t be a major coastal port today if nature had its way with the Mississippi River, according to a University of Idaho professor who worked on a four-year National Academies of Sciences research project on the Louisiana coastline that was published last week.

But those same “well-intentioned” efforts that have preserved the shipping port have disrupted a natural sedimentation process that for centuries kept building up the coastline, as other factors wore it down. Now, the area is sinking, the sea level is rising, and coastal communities are increasingly vulnerable to storm damage – like the havoc wrought by hurricanes Rita and Katrina.

“They’ve been saying these things for years and years, but it hasn’t translated into policy,” said Peter Goodwin, director of the Center for Ecohydraulics Research at UI’s Idaho Water Center in Boise.

The hurricanes hit right as a dozen scientists from across the country were wrapping up the four-year study, entitled, “Drawing Louisiana’s New Map: Addressing Land Loss in Coastal Louisiana.” Goodwin watched CNN in horror from Seoul, Korea, where he was attending the every-other-year convention of the International Association for Hydraulic Research. “It was very, very, very scary,” he said. “As Katrina lined up, anyone who studied down there – you just look at that and you think, ‘This is the worst-case scenario about to unfold.’ “

The scientists’ final report states, “The report is provided at this difficult time in the hope that its advice on restoring and protecting coastal Louisiana can be considered as part of the nation’s strategy to rebuild the Gulf Coast and reduce the likelihood of future tragedies associated with hurricanes in the region.”

If left to nature, the Mississippi would jump to a new channel “every few thousand years,” Goodwin said, but channelization, levies and other big structures now prevent that. Plus, dams upstream block some natural sediment from flowing down the river. The sediment that’s left runs down the channel and into the deep water off the coastal shelf – where it’s essentially wasted, rather than restoring and building back up the coastline.

At the same time, pumping of oil and gas from under the delta and increases in sea level have contributed to continuing erosion of the coast. Though it’s not as bad as it was a few years back – Louisiana lost 39 square miles a year from 1956 to 1978 – the area is still losing 10 square miles of coastline a year. Hurricane Katrina alone wiped out 100 square miles.

Goodwin, an expert on how sediment moves in deltas, marshes and river systems, said the destructive hurricane may be what finally brings the needed attention to coastline restoration. “Although Katrina was a big tragedy, one of the things this will allow is a comprehensive model of the whole area,” he said.

That’s a major recommendation of the scientists’ report, which looked at existing restoration plans and the long-term outlook. They concluded that four of five multimillion-dollar projects that now are planned are scientifically sound, but don’t constitute the kind of big-picture approach that’s needed to address the huge coastline, which stretches over 30,000 square miles.

The fifth project, a $108 million shoring-up of the Mississippi River Gulf Outlet, a little-used artificial shipping channel that’s maintained as an alternate route, would bring little benefit and should be reconsidered, the report found – especially since the controversial outlet could soon be closed.

“It’s a straight shot to the Gulf,” Goodwin said, and some scientists believe it could actually worsen inland damage from storm surges. “That’s certainly one of the issues that’s been raised by people who would rather see the … outlet closed,” he said.

An example of the bigger solutions the report recommends is building a new, second channel for the Mississippi to the west – where the river would be flowing naturally – to allow sediment to be carried there and build up the coastline, while still keeping the current channel open for shipping.

The report also recommends a strategy of “managed retreat” – recognizing that not all the coastline can be saved, and identifying which parts make sense to save, and which to abandon.

“Tough decisions have to be made,” Goodwin said.