Isaac was downgraded to a tropical depression on Thursday and is moving into the central United States.
It left little damage in New Orleans, where stronger barriers were installed after Hurricane Katrina in 2005 but leaving large areas of the region flooded.
A report says that seven tornadoes have spun off from Isaac in Mississippi and Alabama.
A tornado that touched down in Gulfport, Mississippi had caused significant destruction to homes.
Now, there is a potential failure of Lake Tangipahoa Dam in Mississippi’s Percy Quin State Park.
Authorities ordered the immediate evacuation of tens of thousands of residents in nearby communities in Louisiana and Mississippi as a protective measure if the dam burst flooded the areas.
Isaac came ashore late Tuesday as a Category 1 hurricane, with 80 mph winds near the mouth of the Mississippi River bringing along high winds, storm surges, and torrents of rain.
It drove a wall of water nearly 11 feet high inland.
By Wednesday mid afternoon, 19 hours after making landfall, Isaac had been downgraded to a tropical storm.
Anyway since Isaac moves very slowly, it is dumping more rain and together with the threat of storm surges it can cause more flooding in Louisiana.
Isaac that arrived exactly seven years after Hurricane Katrina did not make a direct hit on New Orleans.
It brings slashing rain and wind gusts up to 100 mph that buffeted New Orleans skyscrapers.
In Plaquemines Parish, the storm pushed water over an 18-mile levee and put so much pressure on it that authorities planned to intentionally make a hole in the floodwall to relieve the strain.
Dozens of people were stranded in the flooded coastal areas and had to be rescued.
Plaquemines Parish ordered a mandatory evacuation for the west bank of the Mississippi below Belle Chasse because of worries about a storm surge.
West of New Orleans, Tropical Storm Isaac pushed water from lakes Pontchartrain and Maurepas into parts of LaPlace that caused flooding in St. John the Baptist Parish and victims were evacuated.
The Category 1 Hurricane Isaac hit New Orleans exactly seven years after New Orleans was hit by Hurricane Katrina on August 29, 2005.
So far the new barriers built to protect the city after the 2005 Katrina disaster has not been breached.
Anyway a levee on the outskirts of New Orleans has been breached on Wednesday.
Emergency management officials in low-lying Plaquemines Parish reported the over topping of an 8-foot (2.4-meter) high levee between the Braithwaite and White Ditch districts southeast of New Orleans.
There are reports of people on their roofs and attics and 12 to 14 foot of water in their homes.
The greatest concern is an expected storm surge of between 6 and 12 feet off the Louisiana and Mississippi coasts, 4 to 8 feet along the Alabama coast and 2 to 4 feet on the Florida Panhandle.
Storm surge is when hurricane winds raise sea levels off the coast, causing flooding on land.
Farther south, water was pushed over a rural levee and flooded some homes.
Beach front roads were under water, and more than a half-million people had lost power in Louisiana.
- Photos: Hurricane Isaac Hits Southeast Louisiana
- Hurricane Warnings For New Orleans And Northern Gulf Of Mexico Coast
- Photos: Tropical Storm Isaac Lashed Cuba
- Photos: Tropical Storm Isaac Hit Cuba And Haiti
- Photo: Tropical Storm Isaac In Domincan Republic, Heading For Haiti
- Tropical Storm Isaac Hit Caribbean – Photo