Do note, however, there are apparently some issues with the effect of LA Executive Order KBB-2005-23, and the location of the barge damage, which is likely Industrial Canal, not 17th Street (near the lake).
Most civil engineers familiar with levee design assert that a barge could not cause a breach; but could be drawn to one and sucked through. The live threads have some discussion, I don't have links handy.
There is also an issue with your assignment of September 1 to "The Louisiana governor still doesn't request Federal assistance." See letters of August 27 and 28 requesting federal assistance.
I still haven't developed a handle on the requests for NG assistance (which was also in place before the storm hit, see NG at the Superdome checking people in, etc.), or the lapse in control of civil order, etc. The fact patterns are more complex than any summary can convey.
With regard to the operation of the NG - http://inteldump.powerblogs.com/posts/1126296246.shtml - is one of several sites that may be useful to obtain facts (and conjecture!) about "how things work."