In the Galveston storm of 1900, ALL the children in the orphanage and ALL the nuns were lost. They were swept away in the storm surge. Some of their bodies were found tied together with ropes. The nuns had tried to keep them together.
I don't know the elevation of the NO Superdome but I fear the 20+ foot storm surge.
For what it's worth...it's been reported that the 20+ storm surge for NO is now unlikely.