Random National Security Thought

You know, the hurricane didn't cause the damage to New Orleans, it was the break of the levee (or the equivalent of a levee). So if there had never been a hurricane, couldn't the same disaster have been caused by one single bomb placed along the levee? After all, the possibility of the city being destroyed by a levee break was widely known. And wouldn't the casualty count been greater if the break had come without warning? Are there other parts of our country equally susceptible to such damage at the hands of one bomb? (By the way, that's a picture of Six Flags Great Adventure Amusement Park that is under water).