This is what the SuperDome plan was and it says no food and water to be provided:
Southeast Louisiana Hurricane Evacuation and Sheltering Plan: http://www.ohsep.louisiana.gov/plans/EOPSupplement1a.pdf
The Supersome was designated as a last resort refuge and it says: "Unlike a shelter, there may be little or no water or food and possibly no utilities. A Last Resort Refuge is intended to provide best available survival protection for the duration of the hurricane Only - (my emphasis).
From the City of New Orleans Disaster Preparedness Plan.
The Hurricane Emergency Evacuation Standard Operating Procedure is designed to deal with all case scenarios of an evacuation in response to the approach of a major hurricane towards New Orleans. It is designed to deal with the anticipation of a direct hit from a major hurricane. This includes identifying the city's present population, its projected population, identification of at-risk populations (those living outside levee protection or in storm-surge areas, floodplains, mobile homes, etc.), in order to understand the evacuation requirements. It includes identifying the transportation network, especially the carrying-capacity of proposed evacuation routes and existing or potential traffic bottlenecks or blockages, caused either by traffic congestion or natural occurrences such as rising waters. Identification of sheltering resources and the establishment of shelters and the training of shelter staff is important, as is the provision for food and other necessities to the sheltered. This preparation function is the responsibility of the Office of Emergency Preparedness.