Search-and-rescue operations resumed in heavily flooded areas around New Orleans today, but residents and authorities said Hurricane Issac's destruction was nothing like that seen after Hurricane Katrina in 2005.
Isaac, a slow-moving Category 1 hurricane when it hit the region on Tuesday, is weakening into a tropical storm today.
But it drenched a widespread area along the US Gulf of Mexico coast and could still bring heavy rain and floods as it moves over the central United States - where rain is badly needed - in the next few days.
More than one million residents of Louisiana and Mississippi were without power due to Isaac this morning, according to the US Department of Energy.
Oil production in the Gulf of Mexico was expected to start increasing again, after nearly grinding to a halt as Isaac closed in on Louisiana on Tuesday. Most energy facilities, including key coastal refineries, seemed to escape any Isaac-related damage.
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Multibillion-dollar defences built to protect New Orleans, after it was ravaged by Katrina almost exactly seven years ago, passed their first major test, according to the US Army Corps of Engineers. But massive rains and storm surge from the Gulf of Mexico inundated low-lying communities outside the federal flood containment system protecting the city, forcing the evacuation of thousands of people from their homes and dramatic rooftop rescue operations.
The hardest hit area was Plaquemines Parish, southeast of New Orleans, where floodwaters overtopped at least one levee yesterday and left many homes under about 3.6m of water. Local boats plucked dozens in Plaqemines from the roofs of their houses after earlier deciding they could ride out what compared with Katrina seemed like a small storm.
Parish president Billy Nungesser said US troops and local police were going house to house through the area today to ensure that there were no deaths or injuries. Clearing weather permitted the use of military helicopters to aid in the operation.
In St. John the Baptist Parish, northwest of the city, about 3,000 people were forced to evacuate their homes before dawn today due to storm surges from Lake Pontchartrain and Lake Maurepas, authorities said.
In the town of Slidell, a town of about 27,000 northeast of New Orleans, a levee was breached at about earlier today, and floodwaters were entering the Eden Isle community, local media reported.
Elsewhere, officials today ordered a widespread evacuation along the Tangipahoa River between the towns of Kentwood and Robert due to the imminent failure of a dam in Mississippi caused by rising water from Tropical Storm Isaac.
Due to the imminent failure of the Lake Tangipahoa Dam in Percy Quinn State Park in Mississippi, near the town of McComb, up to 60,000 people downstream in Louisiana need to immediately evacuate, Tangipahoa parish president Gordon Burgess told local television station WWLTV.
The dam is about 161km north of New Orleans, which is not in imminent danger. Louisiana Governor Bobby Jindal has ordered buses to the area to help evacuate residents due to rising waters on the river, Mr Burgess said.
Isaac never came close to the power of Katrina, which was a Category three hurricane on the five-step Saffir-Simpson scale when it smashed into New Orleans on August 29th, 2005.
But President Barack Obama still declared the impact on Louisiana and Mississippi major disasters and ordered federal aid to supplement state and local recovery efforts.
City officials also said Louis Armstrong New Orleans International Airport, which closed late on Monday, would remain shut today until repairs can be done to the damaged lines that supply it with power.
Reuters