My company went through something like this last year, though they had a couple of hours to work with. Luckily I was not one of those directly impacted.

Main impact was to an engineering team in a downtown location. About 150 people were given 20 minutes to pack personal items and important work papers/references. Work items were limited to what would fit in their office trash can. The trash can and the office computers were placed on the office chairs, wrapped up and rolled to trucks which hauled everything to the building I worked in. Facilities people from the entire company descended on the building that was going to flood and moved nearly everything else to the top couple of floors of the five story building. Several engineering integration and test rigs were also hustled out of the building.

The next morning everyone of those people had a new office / cubicle in my building and access to their computers. Good planning and realistic reactions from the top down.

I think they recovered everything out of the building about 2 weeks later, some things quite a bit worse for wear even though they were not under water. High humidity with high heat around polluted flood waters aren't a good combination for paper or electronics to be anywhere near.

-Eric