Large parts of Biloxi, an area east of New Orleans, have been left under water. This image posted on Twitter shows how some main roads are completely submerged.
The National Hurricane Centre has said that Hurricane Isaac has weakened slightly as it has moved inland.
News reporter Maya Rodriguez has tweeted that there are people trapped by flooding in New Orleans.
New Orleans Mayor Landrieu is reported to have said that 70% of New Orleans is now without power.
Local radio station is told that "it doesn't matter if the levels have given way or if they are "over-topping," as there are already reports of 10-12ft of water in homes in Braithwaite in New Orleans.
Latest pictures as Hurricane Isaac makes its way across Louisiana show rain soaked streets and fallen trees as the winds whistles past the battened down buildings in New Orleans.
The centre of Hurricane Isaac is moving inland over southeastern Louisiana.
There have been warnings of flash floods as levees have started to be overwhelmed water around New Orleans, meteorologists and radio stations have been keeping residents up to date on Twitter:
Flash Flood Warning for Orleans, Plaquemines, St. Bernard and St. Charles Parish in LA until 6:45am Wednesday. #lawx
NWS reports: A back levee in Plaquemines Parish is being overtopped..some evacuations underway
Nunguesser: Massive overtopping Eastbank levee in Scarsdale area.. "Cant tell ya" if levee is breached or not