I just heard a brief something about this today but I didn't get the whole story -- the moment I heard that it was a BARGE that broke the levee I was in shock -- how could 'they' (anybody) possibly allow any kind of barges anywhere near the levees with a Cat. 4/5 hurricane coming? WHO was responsible for that cataclysmic fiasco?
According to the accounts I have seen, no one has said that a barge broke the levee during the storm. The supposed witness said he saw it after the hurricane had already passed. Remember the timeline - Monday evening the levees were reported to be holding and no breaches were reported.
I posted the following analysis in an earlier discussion. I believe it more acccurately describes what probably occurred.
What I suspect happened was that the barge didn't "smash" through the levee - it was "pulled" through. Whoever witnessed it did not really understand the science of what they were seeing.
Even a huge barge does not possess the mass to smash through a wall of earth the size of a levee. There is one force, however that can - the slow, relentless pressure of water against a semi-permeable surface.
What happened was that because a great deal of the material used to construct the levees was the most easily available loose delta soil and miscellaneous debris, which will not compact and solidify well, as the water pressure increased water began to actually penetrate and seep through the levee walls. As this process accellerated, the seeping water began to, in a very real sense, actually flow through the levee walls. As it did the walls were gradually eroded from within.
What this meant was that an observer viewing the levee from above would be seeing what appeared to be a levee that was "holding", but it would really be washing away below, out of sight. This process would continue until enough material was eroded to allow the visible top of the levee to collapse and then observers could see the water pouring through. In reality, however, the water had been pouring through long before that.
That's what the observer of the barge saw - it didn't smash through, it was drawn by the invisible pull of the water directly to that point on the levee where the unseen flow caused the top of the levee to crumble and collapse.
There is an important lesson in this scenario that needs to be remembered whenever the immediate crisis is over and talk turns to the decision whether to rebuild New Orleans on the present site or relocate it. Because of the nature of the construction of the current levees, they probably would not have held for long even if they had been twice as high.
Some serious study needs to be given as to just what types of levee material and construction would be strong enough, and also whether even good, solidly-built levees would have the necessary sub-statum support to keep them from sagging and cracking as the already-observed area-wide compaction and sinking progresses. The dynamics of this collapse provide strong arguments for the case to relocate the city.