Artificial Islands Can't Save La. Coast, Say Geologists

Louisiana Governor Bobby Jindal has a plan to save his state from both the BP oil slick and future hurricanes: Rebuild and reinforce barrier islands to shield the shorelines.

Sites have already been approved for dredging, according to reports, and the plans have been rushed to the federal government for expedited approval.

"It would be so much easier to clean oil off this (dredged) sand than to deal with in our marshes," Jindal said in a recent news conference. 

Artificial islands, dikes and other sorts of coastal engineering projects have a long history, and they can help some coastal areas in some ways. Aside from the fact that there may not be the months or years needed to build such barriers before the oil arrives, there are a couple of catches with the sand barriers proposed by Jindal, say independent experts.

First, the project will cost enormous sums of money to implement and maintain. And second, it won't work on the Mississippi delta's rapidly subsiding landscape.

"This is another one of those myths that people have in their minds about Louisiana geology: That the barrier islands are the first line of defense against hurricanes," said Roy Dokka, executive director of the Center for GeoInformatics and a professor at Louisiana State University. "That's just not true."

Unlike along the coast of Florida or the Atlantic seaboard, barrier islands in the Mississippi Delta area are all sinking, just as the delta sinks, Dokka explained. It's the way large river deltas work as sediments pile onto them from the rivers and press down on the crust of the Earth or slowly slump into the sea. That sinking feeling is accentuated by rising sea levels caused by global warming.

Louisiana's barrier islands are all doomed, as were the barrier islands that came before them which are now part of the sea bottom off shore. It's part of a process that has been going on for eons.

"Barrier islands are the tombstones of the delta," said Dokka. The islands were once part of the mainland, then were cut off as the land subsided. "So when you see barrier islands in Louisiana it means its time is almost up."

Trying to rebuild such islands or create new ones, therefore, ignores the basic geological processes of the region. But that hasn't stopped people from already trying.

Take, for instance, the efforts to build up Louisiana's East Timbalier Island, said Dokka. A lot of money was spent dredging and building up the ground. Yet today, just a few years later, that work is under several feet of water. In order to keep such projects from literally losing ground, islands would have to be continually rebuilt.

"You are talking about a public works project that will never end," said Dokka. And so the cost is not in the hundreds of millions, as Jindal has said, but would be incalculable.

The Mississippi delta isn't the only region where geo-engineering is meeting its match. Low-lying places in California's Sacramento River Delta and San Francisco Bay are also facing the reality of sea level rising and exposing new areas to potential flooding.

Even Holland has begun to acknowledge that its dikes are no match for sea level rise, and so people are moving further from the sea, said geologist and coastal hazards researcher Gary Griggs of the University of California at Santa Cruz.

"It's a massive problem and it's a global problem," Griggs told Discovery News. Unfortunately, when there are lots of factions demanding loudly that something be done, as in Louisiana, seemingly simple ideas that have little scientific basis can get a lot of traction.

"For a complicated problem there is always a simple solution that's always wrong," said Griggs.