Shrinking La. Coastline Contributes To Flooding
Tuesday, August 30, 2005
Two months ago, Sen. Mary Landrieu (D-La.) told an audience of congressional staffers and scientific experts the federal government needs to spend billions of dollars over the next two decades to restore her state's wetlands. She warned that intentional rerouting of the Mississippi River over the past century, coupled with rising sea levels due to climate change, had eroded Louisiana's natural buffer against massive storms.
"This is not Disneyland. This is the real deal," Landrieu said, referring to New Orleans's vulnerability to hurricanes. "The French Quarter could be under 18 feet of water. It would be lost forever."
Although the extent of the damage that Hurricane Katrina inflicted on the city remains to be assessed, several experts and government officials said the storm highlights the importance of restoring Louisiana's coastline closer to its natural state. Lawmakers have pushed since the 1920s to create a straighter Mississippi River that provides easier passage for ships and better flood control, but federal officials now back a $14 billion plan to restore more meandering waterways, which in turn would deposit new silt on the state's shrinking coastal wetlands.
"Indeed, we have the technology and ability to engineer our way out of this and put in something that's more natural and sustainable," said Gen. Robert B. Flowers, who headed the Army Corps of Engineers from 2000 to 2004.
The Mississippi used to deposit vast amounts of sediment that built up the Delta as the water reached the ocean and the current slowed, but now this silt gets carried straight out to sea through a channel. As a result, the coastline has shrunk dramatically since 1839; Louisiana loses 25 square miles of coast a year.
Shirley Laska, who directs the Center for Hazards Assessment, Response and Technology at the University of New Orleans, said state and federal officials, in building higher levees to maintain cities such as New Orleans, are consequently ill equipped to handle natural disasters that might threaten the port city.
"There is no safe place in New Orleans" in the case of a hurricane, she said in June at the congressional briefing. "The culture does not yet know how to do this. Unfortunately, we are the test case."
Global warming has made the task tougher, according to some scientists, because it leads to higher seas and more extreme weather. Thomas R. Knutson, a research scientist at the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory in Princeton, N.J., said warmer tropical sea temperatures -- which have risen by almost one degree Fahrenheit since the 1970s -- may lead to more violent storms in the next few decades.
"This increased warming allows for the possibility of more intense hurricanes than we have in the current day," Knutson said. "When you increase the temperature, you expand the envelope for extreme weather."
Also, global sea level has risen more than an inch over the past decade, which increases the danger from storm surges. Kevin E. Trenberth, who heads the climate analysis section at the nonprofit National Center for Atmospheric Research, said all of these environmental factors help explain why flooding from Hurricane Katrina may stretch as far north as Canada.
"There's a clear signature of global warming in this," he said. "While it's not the dominant factor, in some things it becomes the straw that breaks the camel's back."
Landrieu did achieve part of her goal in late July, when Congress approved a massive energy bill providing $1 billion for Louisiana and other states to shore up their coastlines. Just over half the money will go to Louisiana, with smaller portions going to Texas, Mississippi, Alabama, Alaska and California.