This statement is valid for today.
Unfortunately, the Mississippi River is not static, and brings more silt every day, so eventually the storm needed to breach the levees will be much smaller than what would be required today.
Excuse me, but what do you think "Mississippi river silt" has to do with breaching levees?? The levees that might be breached are on Lake Ponchartrain---not the Mississippi, and the silt load of the Mississippi is dropped WAY out in the Gulf (which is why the swamplands are eroding---LACK of silt, not too much).