8/31/2005
Development, nature eroded region's defenses

By Traci Watson and Tom Kenworthy, USA TODAY

People in southern Louisiana and the Gulf Coast have learned a hard lesson:
There's a price to be paid for taming the Mississippi River.
Decades of flood-control efforts to protect New Orleans and other places,
combined with the region's huge oil and gas investments, have contributed
heavily to the destruction of coastal wetlands that can help tame the fury
of storms like Hurricane Katrina, say scientists and government officials.

Controlling the Mississippi has starved the marshes south of New Orleans of
the fresh water and sediment needed to sustain them. Spring floods that once
replenished the wetlands are funneled into the Gulf of Mexico.

The engineering of the river has "basically brought the Gulf of Mexico right
to the doorstep of New Orleans," says Val Marmillion, a consultant to
America's Wetland, a group that lobbies to restore the region south of New
Orleans.

Scientists say there is no doubt that natural features can blunt a storm's
power. Wetlands suck up surging waters. Barrier islands absorb some of the
force of the wind and waves. They "provide a natural buffer," says Jeff
Williams of the U.S. Geological Survey.

But in recent decades, development and natural causes have compromised what
oceanographer Abby Sallenger of the U.S. Geological Survey calls the "first
line of defense."

In the past 75 years, enough wetlands to cover the state of Delaware have
vanished from Louisiana's coast. Louisiana's barrier islands are also
disappearing, Sallenger says. The Chandeleur Islands are eroding at a rate
of 33 feet per year on one side.

Some of the changes are natural. Southern Louisiana has been sinking for
centuries. The sinking is also caused by oil and gas production, which sucks
fossil fuels and water out of underground reservoirs, says Bob Morton of the
U.S. Geological Survey.

Man's impact has been considerable, beginning with the construction of
levees and concrete channels to control the Mississippi after a devastating
1927 flood.

"It was for the nation's benefit," says Sidney Coffee, a coastal issues
specialist. "But the unintended consequence is that the natural annual
overflow of sediment and fresh water has been cut off from the delta."

Wetlands loss has slowed recently but hasn't stopped. State and federal
officials have pushed a $14 billion plan to rebuild wetlands over the next
30 years, to be funded by oil and gas royalties. But budget constraints in
Washington have stymied the plan, though Louisiana will receive $540 million
under the energy bill enacted earlier this month.

In Mississippi, the problem is a surge in development of casinos and other
buildings in vulnerable areas. That eliminated dunes that provided
protection, Williams says.

"You have buildings and people and infrastructure in very high-risk areas,"
he says.

Contributors: Watson reported from Washington, Kenworthy reported from
Denver.

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