Choices engineered city's vulnerability

Katrina's Wake

September 04, 2005|By Alec MacGillis and Frank D. Roylance | Alec MacGillis and Frank D. Roylance,SUN STAFF

Hurricane Katrina might have started as a natural disaster, but the subsequent flooding of New Orleans was a human failure, brought on by people who set the stage for destruction and by leaders who, despite ample warning, did not act to prevent it.

The timeline of responsibility extends back nearly three centuries, from the decision to site the city in a strategic but geologically vulnerable spot, to the generations-long effort to bend the flow of the Mississippi River to commercial needs, to the shortage of funding to expand a flood protection system that was widely known to be inadequate.

"There are things to be frustrated about; there's a lot to say `if only' about," said Len Bahr, director of applied coastal science programs in the Louisiana governor's office. "Some of us knew many years ago that this was bound to happen. ... It's wishful thinking, I guess, but it's frustrating now to see all this damage down here and wonder how much could have been offset."

When Katrina hit one week ago, the city was in a less than ideal position to survive it because of a long string of developments:

Many of the levees fronting the Mississippi River and Lake Pontchartrain, the huge, brackish Gulf of Mexico inlet north of the city, were built to handle only a Category 3 hurricane, not a Category 4 or 5, despite evidence that stronger storms are not unheard of; Katrina was a Category 4, though its center skirted New Orleans to the east. Plans in recent years to upgrade levees have been stymied by a lack of federal funding.

The city sits mostly below sea level, and it has been sinking farther every year. Subsidence is natural, but it has been accelerated by the lack of sediment being carried down by the Mississippi to replenish the delta, a result of upriver dams and levees. Also contributing are the levees in the city, which keep sediment from being deposited; the constant pumping of rainwater out of the city's soil, which is necessary to keep it dry; and oil and gas extraction in the area.

As the city has been sinking, the water's been rising - in the gulf and Lake Pontchartrain, part of the universal rise in sea levels, as well as the water in the river, which is flowing higher because of levees built to prevent flooding upstream.

Marshland and barrier islands have been vanishing, depriving New Orleans and its environs of a crucial buffer against powerful hurricanes. Some of the erosion is natural, but it is exacerbated by the lack of sediment being carried down the river, and by the decades-old decision to keep the Mississippi flowing in its current course, rather than let its outlet migrate naturally westward, and thereby distribute sediment more broadly.

"The situation is really the cumulative effect of a variety of human and natural processes that have been going on for years," said S. Jeffress Williams, a U.S. Geological Survey scientist with 20 years' experience studying Louisiana. "Cumulatively, the wetlands and the coast have just seriously deteriorated."

When President Bush spoke after the flooding last week, he said, "I don't think anybody anticipated a breach in the levees."

But in fact, scientists and civil engineers have been warning for years that a Category 4 or 5 hurricane would eventually strike, overwhelming a levee system on Lake Pontchartrain and the urban canal system that drains into it.

"The odds caught up with them," said Gerald E. Galloway, a professor of civil engineering at the University of Maryland, College Park.

In the past several years, in-depth reports in The Times-Picayune newspaper, National Geographic and Scientific American have detailed both the nature of the threat and the potential consequences - with uncanny accuracy. And years ago, Risk Management Solutions, a disaster risk-modeling firm in California, pointed out that storms of Category 4 or more strike within 100 miles of New Orleans about once every 35 years on average.

Katrina was the fifth to make landfall in the area since 1899. Hurricane Betsy was a Category 4 storm when it struck 80 miles west of New Orleans in 1965. Hurricane Camille was a Category 5 storm when it struck just east of New Orleans in 1969.

Public officials may have been lulled by a reduction in the frequency of hurricanes in the Atlantic and the gulf after 1970. But the period of relative quiet ended in 1995. Researchers at the National Hurricane Center and elsewhere have been warning since then that the region faced a period of increased hurricane activity that could last for 20 to 40 years.

The threat of hurricanes and flooding has faced New Orleans since its founding early in the 18th century, in a location near the mouth of the continent's greatest river system.

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