A suggestion the water if from the river does not mean it is. From what I see there is no major break in the River levee.
http://www.freerepublic.com/focus/f-news/1473615/posts?page=30#30
In that photo the lake is to the north, the river is to the south. The section that is being flooded, Arabi, has been flooded for at least 33 hours, and had the water up to the rooftops for almost that long. Reports for 30 hours have been that the there was an overtopping from the Mississippi River that was flooding this section of Arabi, including reports from the mayor's office and the Army Corp of Engineers.