The hurricane was categorised downwards from force three to two just before it hit land near Cocodrie, a thinly populated town west of New Orleans known for its fishing and oil industries. Dramatic television footage showed waves being forced by winds of up to 110 mph over the tops of the flood defences on the west side of the city, in a worrying echo of what happened in 2005.
Power supplies were cut to large parts of New Orleans as falling trees downed electricity lines and flattened several homes.
Crucially, though, sea level surges were this time mercifully limited to up to 9ft in some places, markedly less than the 27ft surges that were seen with Katrina.
As New Orleans heaved a huge sigh of relief, towns to the west, such as Lafayette and Baton Rouge, remained imperilled. Bobby Jindal, Louisiana’s governor, warned that cataclysmic flooding could still be brought by the tail end of the hurricane.
While Gustav failed to live up to the terrifying standards set by Katrina, it still succeeded in leaving both communal and political chaos in its wake. Almost two million people fled the Gulf of Mexico, the largest evacuation of its kind, turning New Orleans and other communities along the coast into virtual ghost towns.
The first day of the Republican Convention in St Paul, Minnesota, was also disrupted as John McCain and his advisers struggled to find the appropriate tone. They were acutely aware of the need to avoid any association with President Bush’s handling of Katrina, which was criticised for being negligent and insensitive, yet with the threat of Gustav diminishing they were also under pressure to salvage the wreckage of their own convention.
McCain switched his planned appearances to focus on disaster relief in Ohio and a visit to Mississippi. Bush cancelled his speech to the convention and travelled instead to Texas, from where he might still address delegates by satellite link.
At an emergency centre in Austin Texas, he acknowledged that planning for Gustav marked an improvement over the events of 2005. "The coordination on this storm is a lot better than on – than during Katrina," he said.
McCain and Bush’s absences left their spouses, Cindy and Laura respectively, as well as the newly appointed vice-presidential candidate Sarah Palin, the governor of Alaska, to hold centre stage at the convention.
About 1,600 died in Katrina when 90,000 square miles were flooded, including 80 per cent of New Orleans. The lack of advance planning in 2005, and the sluggish federal response by the Bush administration, has gone down in history as one of America’s most shameful moments.
By contrast, both federal and local governments were quick this year to put emergency plans in place. Fema, the federal emergency management agency that was heavily criticised over its handling of Katrina, this time effected a five-day plan under its current chief, the homeland security secretary Michael Chertoff, that saw almost 90% of the region evacuated.
Locally, New Orleans enacted a dawn-to-dusk curfew designed to prevent the epidemic of looting that broke out in 2005. In further echoes of Katrina, the streets of the city were lined with heavily armed police officers – though this time they were spared scenes of lawlessness.
As the storm passes over the area, and the threat recedes, questions are likely to follow over the extreme nature of the preparations. The mayor of New Orleans, Ray Nagin, appeared to go beyond the measured reports of the hurricane forecasters in encouraging the city’s residents to evacuate.
On Sunday night, he called Gustav the "mother of all storms" and warned anyone who ignored the exhortations to flee that they would be "on their own".
"It was absolutely the right message to send," Nagin told ABC News on today in defence of his earlier remarks.
Katrina strengthened as it came ashore into a category 4 hurricane, and did so towards the north and east, pushing the waves directly towards New Orleans and breaching the levees on the east of the city.
Gustav swung to the northwest, putting New Orleans on the "dirty" side of the hurricane where rainfall is heavy but the storm surge is milder.
It hit the levees on the west of the city, coming at an angle with lesser force. Though the waves were seen to be sloshing over the flood walls, the defences were expected to hold.
"The system is not inundated, it is not a breach. We are confident in the stability of that wall," said a spokeswoman of the US Army Corps of Engineers.
Though the levees looked likely to retain their integrity on this occasion, there are also likely to be questions once the initial crisis has passed about the pace of repairs to New Orleans’ defences. The eastern wall, breached in 2005, has been repaired by the army corps in a rebuilding programme scheduled to last until 2012, but the threatened western wall has yet to be reinforced as a result of on-going under-funding.
With the frequency and force of hurricanes in the region of the Gulf of Mexico also appearing to be on the rise, some say as a result of global warming, there is bound to be renewed soul-searching over the long-term viability of a sub-sea level city such as New Orleans.