When I worked for the county one of my favorite brochures that Emergency Management had on display was the one on making a portable toilet. When storms hit not only will you lose your water supply, but with the electricity out all of the sewer lift stations will stop working. No lift stations = no working toilets.
Making an emergency toilet is super easy. All you will need is a five gallon bucket, toilet seat from one of your bathrooms, large trash bag and kitty litter. Place the bag inside the bucket, pour in several inches of kitty litter, then place the seat on top. Periodically throughout the day pour a bit more kitty litter in to cover fresh waste.
Every couple of days replace the bag. Put the well sealed, used bag away from the house and water supplies.
Where my family comes from up in Illinois everyone I knew had kept the old outhouses on their property in good repair. You just never knew when you might need it!