Around the world, for decades, the US has brought food, water, and other supplies in by parachute when runways are not available or are not safe.
The solution in NO should have been to parachute the necessities in at the earliest possible moment that it became clear that all other alternatives would allow the situation to degrade drastically through added delay.
A possibility, but I'd venture they did not do that because of logistical support.
Without logistical support on the ground the supplies either don't get distributed, or wind up in the hands of the armed "looters" who would undoubtedly use it to increase their strenght, ala Somali warlords.
I'm 100% certain all of these ideas were thought of and discussed, and ultimately the decison was made to execute in the manner we are seeing now. Most likely the determining factor was the extreme number of people who remained during a "mandatory" evacutaion.
If you want to blame anyone blame the mayor, the governor, and most of all the slackers who didn't evacuate. Had all those with the abilty to leave left, the resources would most likely have been plentiful for those remaining.