We keep hearing about the Levees were blt for a Cat 3 and not a Cat 4 or 5 when Katrina hit. However, as is noted here katrina didn't hit N.O. directly and the number of "dodging the bullet" claims. Yet the levee didn't break during the storm, it broke after the storm had passed over. I heard one report that someone saw a large ship or barge that was lose and hit a levee and caused the breach, makes sense to me.
I just posted on another thread if any one saw that report and then I click on this one and start reading and you answered my question.
Go to Gathering Storm For The Media and click on # 63 post and you will find my question and my thoughts.
I heard the same thing about someone witnessing a grain barge breaching a levee. That said, there were several breaches which seem to have occurred in short order.