NautiNurse:
"How deep is Lake Ponchartrain?"
I don't know, but I suspect it isn't very deep. The "container" is essentially sand, which has a low angle of repose.
The key right now, is how high the surface of Lake P. is relative to normal. Unless the flooding in downtown NO moves enough water to lower it, that level is how deep NO will flood. Keep in mind, major breaches on the River side (which I have not seen yet) mean that the storms effects over the entire Mississippi watershed (which are still in progress) will contribute to the final levels in NO.
At this point, it is not the flooding we need to be concerned about, it is the RATE of flooding. Rising water is infinitely preferable to rushing water.
4.5 inches higher than normal, down from seven above at 10:30 yesterday. It may have gone higher the sensors went off line.