Building where I used to work downtown is one of the few buildings that has a plan for next time. (They got severely flooded by Sandy)

They have an 8-foot perimeter wall that can get setup in a few hours. They test it annually to ensure it will hold back water for several days. You can see the perimeter installation posts in the concrete around the building. Seems like a much better idea than sandbags. Also their vulnerable stuff like network and power access is now moved up from the ground floor.