There are hurricanes and hurricanes - and then there was hurricane Katrina. On average half a dozen of these fearsome Atlantic storms hit the mainland US every year, but in terms of quantity and quality the 2005 season rewrote the meteorological record books. There were a record 27 named storms - so many that the standard alphabetical list of first names was exhausted, and Epsilon, the fifth letter in the Greek alphabet, was used to denote the last of them, a "weather event" that mercifully confined itself to the empty expanses of ocean.
Of those 27 storms, 15 turned into hurricanes, with maximum sustained winds of more than 75 mph. Three of them, for part of their lives, became Category 5 monsters, with sustained winds in excess of 155 mph. One of them was Katrina. Though it had weakened to "only" a Category Three by the time it smashed on to the north central Gulf Coast in the early hours of 29 August 2005, it was still a storm for the ages, with hurricane force winds stretching 100 miles from the eye in all directions. It finally petered out in eastern Canada three days later. But along the coast of Louisiana, Mississippi and Alabama, the three states that bore its brunt - across an area the size of England - it had left death, devastation and distress unmatched by any American natural disaster in modern times.
Not only were individual lives and local communities affected, Katrina caused the inundation of New Orleans, one of the country's most historic cities, changing it probably for ever. Its impact was felt by the entire national economy, as the hurricane shut down oil production in much of the Gulf and knocked perhaps $30bn (£16bn) off gross national product in the third quarter of last year. Oil and petrol prices soared, while the political standing of President Bush plummeted as a result of the federal government's botched and tardy response to the storm. Suffice the Presidential phrase, "Brownie, you're doing a heckuva job," to sum up the ineptitude. The "Brownie" in f question was the hapless Michael Brown, the director of Fema, the federal disaster agency, who was sacked a few days later.
Other hurricanes have been stronger than Katrina - Camille, for example, which struck Louisiana in 1969 with winds of 190 mph, and Andrew, which cut a 165 mph swathe across southern Florida in 1992. But both were far smaller in extent. "Camille was nothing compared to this," a couple of local residents of Slidell, a small town across Lake Pontchartrain from New Orleans, told me when I arrived there on 31 August. They were sitting on a road along the lake front, opposite the empty space where their house had once stood. All around was a world in fragments. Trees were snapped like matchsticks. Downed powerlines drooped from their branches or lay tangled on the ground. Of the few trees that remained more or less intact, one had a refrigerator wedged into its branches. Great piles of debris were all that remained of houses. Furniture, food, linen - everything from children's toys to the entrails of air-conditioning systems - were scattered as far as the eye could see.
What was different about Katrina, they said, was the length of the storm, some 10 hours from beginning to end, and the size of the storm surge. Think hurricanes and you think of mighty winds. But the real damage is done by water, in Katrina's case a storm surge 20 feet high that raced tsunami-like hundreds of yards inland, sweeping all before it.
The figures tell their own story. At the most recent count, 1,836 people lost their lives as a result of the storm, with a further 700-odd still unaccounted for almost a year after the event. Katrina was the deadliest hurricane since 1935, when there were no computers to give prior warning of a storm's course, speed and strength. Thus far, Congress has allocated over $100bn (£53bn) in disaster relief and reconstruction, making Katrina the costliest natural disaster in US history. If disruption to the wider economy is included, the final bill could top $150bn, or f £81bn. And then there is the human and social suffering, and the collective psychological trauma to the wealthiest country on earth as it discovered a third world in its midst - and, initially, produced a rescue response to match.
The flood waters have long been pumped out of New Orleans, washed away highways have been restored, and the touristy parts of town are again hustling for business. But a year on, miles-long expanses of poorer neighbourhoods stand abandoned, probably never to be rebuilt. Pre-Katrina, 450,000 people lived in the city. Today its population is 200,000. Many of the evacuees, now settled in places such as Houston and Atlanta, will surely never return. Even pre-Katrina, New Orleans was arguably the worst-run city in America, a metropolis as famous for crime and corruption as for the delights of jazz and Mardi Gras. For all the bold pledges of recovery, the great storm of 2005 can only have hastened that secular decline.
To the east, along the 90 miles of Mississippi's coast, if anything the damage was worse. No fewer than 15 historic districts, many of them containing magnificent antebellum (pre-Civil War) houses, were wiped out. Between the towns of Waveland and Bay St Louis, which contained 100 listed buildings, only one was left standing after the hellish winds and 30-foot storm surge had struck. And these were structures that had survived Camille 36 years earlier, and were considered indestructible. The damage extended 150 miles inland.
Now we are in the midst of 2006 hurricane season. As I write, tropical storm Chris, the third named so far, is gathering strength north of Puerto Rico, headed for Cuba, Florida, or perhaps further north on the US East Coast - who knows. Whatever happens, though, it is unlikely to match Katrina.
'In the Wake of Katrina', a book of 50 photographs by Larry Towell, is published by Chris Boot, £15. To order your copy at a special price (with free p&p) call Independent Books Direct on 08700 798 897Reuse content