[John Jamieson]

I would think the canal would be below the lake level and pumps would be used to pump water into the lake. No flow would go the other way???

[kingu]

The canal is below the lake level but above ground level and is where a lot of water gets dumped when they're trying to drain other parts of the city.. IE: the western portion of the city dumps into that canal, with the breach, the western portion can't pump without putting in more water into the eastern portion.

Effectively, half of the water pumped out of the western portion of the city since the hurricane started pouring rain down is now flowing into the eastern portion (downtown area). The Corps aren't in panic mode because they need the daylight to move heavy machinery through a town with thousands of fallen trees, downed power lines and other debris. At least this is my take on all of this - your mileage may vary.