Most of the food is underwater and either inaccessible or destroyed. Many hotels, hospitals, and other facilities that have large food service operations, have those operations primarily on the first floor -- wiped out in most cases. Store shelves have all been emptied, with most of the food from them eaten, and a little no doubt hoarded by the few people who have anywhere to hoard it. Relief workers are bringing in food and water as fast as they can, but surrounding areas are also in bad shape, there's only one passable road in/out of the city, and many of the helicopters available are too busy evacuating hospital patients and critically ill or wounded people, and dropping sandbags on the levees, to be used for transporting supplies. Both airports are underwater.
So, I guess we just let the people at the dome die?