America's Wetland director warns of tougher hurricane seasons

Hurricane Isaac flood waters cover LA. Hwy. 23 in Plaquemines Parish in this Aug. 30, 2012 file photo (John Snell)
Hurricane Isaac flood waters cover LA. Hwy. 23 in Plaquemines Parish in this Aug. 30, 2012 file photo (John Snell)

New Orleans, La. -- Decades before the modern warning systems now in place, and long before forecasters started naming hurricanes, Galveston, Texas suffered the greatest loss of life from a natural disaster in U.S. history.

Late on September 8, 1900, a Category 4 hurricane slammed into the then-booming Texas city, claiming an estimated 6,000-12,000 lives.

Although Hurricane Isaac will never rate with that notorious storm, the two share one surprising statistic -- each generated a surge of roughly 15 feet.

The U.S. Geological Survey estimates the peak surge for Isaac at nearly 14-and-a-half-feet, recorded by a portable monitoring device stationed at Pointe a la Hache.

A series of recent hurricanes, including Katrina, Rita, and Ike, have prompted forecasters to warn there is only a limited correlation between a storm's category number -- its wind strength -- and its potential surge.

Isaac, which produced tropical storm force winds for a 54 1/2 hour period, whipped the Gulf of Mexico into a frenzy, delivering a surge well beyond the expectations of most people who decided to ride out the Cat. 1.

Val Marmillion, managing director of the America's Wetland Foundation, believes another important factor contributed to Isaac's surprising punch.

"Isaac is definitely a consequence of the land loss," said Marmillion, whose group is dedicated to spreading to the nation word of Louisiana's coastal crisis.

Marmillion argues Louisiana faces a triple threat of land loss, rising sea levels due to climate change and subsidence.

"The consequence of that is we're going to have longer storms and more intense storms," Marmillion said.

Earlier this year, an Entergy study predicted that, without better defenses, people in south Louisiana are likely to experience Katrina-like storms twice in every lifetime.

Even assuming there is no man-made climate change, Louisiana suffers what scientists call "relative sea level loss."  Cut off from the Mississippi River's land building material, the ground sinks as much as three feet in one century, according to a UNO study.

Marmillion points out Entergy was "worried about their power grid.  Sure enough, we've had real, serious problems with a Category 1 storm for the first time ever."

Only a few weeks after Katrina, Hurricane Rita plowed into the Texas and Louisiana coasts, producing 15 feet of surge in southwestern Louisiana.

It could have been even worse.

A U.S. Army Corps of Engineers study in 2007 concluded that the surge fell by one foot for every 2 to 3.6 miles of Louisiana wetlands.

Marmillion notes surge models have increased the inflow of water dramatically over the last 20 years.  "We're going to have a lot more of this," he warned.