LONG before Katrina struck, the possibility of a direct hit on New Orleans had become a clich茅 among disaster experts. It was the scenario conjured up by anyone who wanted to speculate on the worst of all possible worst cases. Last week the reality became abundantly and tragically clear.
After hurricane Ivan veered from its original New Orleans-bound course last year, Shirley Laska of the Center for Hazards Assessment, Response and Technology at the University of New Orleans speculated on the destruction that would have occurred had it scored a direct hit. 鈥淚t would undoubtedly be one of the greatest disasters, if not the greatest, to hit the United States,鈥� she wrote. 鈥淗urricane Ivan had the potential to make the unthinkable a reality. Next time New Orleans may not be so fortunate.鈥�
The fact that a disaster on this scale was so widely predicted must raise questions about whether enough was done to prepare for it.
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The first shock was the storm鈥檚 power. 鈥淭he strength of Katrina took everyone by surprise,鈥� says Kerry Emanuel, a hurricane researcher at the Massachusetts Institute of Technology. Hurricanes get their energy from warm ocean waters, but in the Gulf of Mexico there is a built-in safety mechanism that usually calms hurricanes before they hit land. That is because the warm water on the surface gives way to cooler water below about 20 metres. So when a hurricane passes over and churns up the sea, it brings this cool water to the surface, calming the storm.
鈥淎 few dozen sensors costing a few dozen thousand dollars each was all that was needed to predict Katrina鈥檚 intensity鈥�
But with Katrina this didn鈥檛 happen. The hurricane followed a flow of warm water called the Loop Current, in which warm water extends down to 100 metres or more, increasing the storm鈥檚 intensity to category 5.
This could, however, have been predicted. All that was needed was for hurricane monitoring flights to drop a few dozen sensors known as AXBTs (airborne expendable bathythermographs) into the water ahead of it. AXBTs cost just a few thousand dollars each and measure the temperature profile of the water down to about 200 metres. This is precisely the information needed to make more accurate forecasts: 鈥淚t鈥檚 a no-brainer. It鈥檚 not like we have to spend millions,鈥� Emanuel says. He blames inter-agency bureaucracy for not making this happen.
The logistics of dealing with the extensive flooding in the aftermath of a hurricane have also been analysed. A year ago, disaster relief experts conducted a desktop simulation exercise dubbed hurricane Pam, in which a category 4 hurricane 鈥� the force at which Katrina made landfall 鈥� hit New Orleans and caused storm surges to overtop the levees, leaving 400,000 to 500,000 homeless from flooding.
Yet the lessons of this exercise appear to have been ignored by its organisers, the Federal Emergency Management Agency (FEMA) and the Louisiana Office of Homeland Security and Emergency Preparedness. 鈥淚t was a great exercise, but I鈥檓 not sure the planned follow-on was funded,鈥� says Bill Massey, former hurricane supremo at FEMA and a consultant to the hurricane Pam exercise.
His fear, like that of many other commentators, is that the money and personnel to act on the exercise leaked away into the federal Department of Homeland Security, which was set up in 2003 in response to the 9/11 attacks. 鈥淭he emphasis, unfortunately, is on terrorism,鈥� says Massey.
Stephen Leatherman of the International Hurricane Research Center at Florida International University in Miami questions whether some parts of New Orleans that were destroyed by the recent floods should be rebuilt. 鈥淣ew Orleans is our Bangladesh,鈥� he says. 鈥淲e can鈥檛 rebuild it the way it was.鈥�
The city鈥檚 most prized assets, including the historic French quarter, the port, the university and high-rise buildings, should be protected with a sea wall much stronger than any levee, Leatherman says. Existing levees might need to be raised, at a cost of $100 million for every extra 30 centimetres.
But what of the surviving population in poor and less well protected districts. Should they return and rebuild their wrecked wooden houses, or seek a safer life elsewhere? A study published in 1996 after hurricane Andrew hit Florida in 1992 suggests that many will not (Demography, vol 33, p 265). Andrew displaced 353,000 people from Dade county, of which 40,000 did not come back.
Storm soothers
The best way of reducing hurricane damage would be to prevent the storm striking a city at all. Although this has never been done, there are numerous ideas for how to do it.
One strategy is to cover the ocean ahead of the hurricane with a thin layer of fish oil, which would disrupt the flow of energy from ocean to atmosphere. But experiments in 2002 by Kerry Emanuel at Massachusetts Institute of Technology suggest that winds could break up the oil layer, preventing it from having any effect.
Ross Hoffman, at climate consultancy Atmospheric and Environmental Research in Lexington, Massachusetts, has suggested nudging a hurricane off-course. This exploits the idea that a small change to a chaotic system such as a hurricane can produce large effects. But doing the nudging, possibly with space-based reflectors to heat up the atmosphere, and predicting its effects are nowhere near practical yet (快猫短视频, 27 July 2002, p 28).
Then there are legal issues. Nudge a hurricane and you could be blamed 鈥� and sued 鈥� wherever it goes. And there will be tough decisions. For example, choosing between a category 3 storm hitting Pensacola and a category 4 hitting New Orleans is easy in cold rational terms, says Emanuel. 鈥淏ut the people of Pensacola may have something to say about it.鈥�
Justin Mullins
