I remember watching a report on an animal rescue group that goes into flooded areas to rescue abandoned pets. I know we all say we'll take the cats with us, but unfortunately that's not always possible. If someone comes to rescue you from a flooded area, they will not permit animals becuase they take up to much room, and aren't allowed in human shelters.
The group said the best thing you can do in a flood is to move litterbox, food, and water to the highest point in your home. Leave an open bag of food, and fill as many dishes as you can with fresh water (if possible). Get a collar with ID tag on the cat(s). Also, leave a carrier (if you have one) and make sure to put your name on it. This group accepts requests from people, and with permission will break into your home to rescue your pets. The worst thing you can do is open windows and allow the pets to escape, because they may drown, get hurt, or never be found. Once they rescue animals, there's a temporary shelter set up and you can come claim yoru pet. ID and a picture of the pet is the best way to guarentee ownership.
I wouldn't know what to do in the case of a fire or earthquake. Again, I live in Ohio... sure, we're overdue for a huge earthquake (like the one that happened in the Pacific), but the possibility of it happening during my lifetime is slim. I just make sure that I have enough carriers for all the cats, so if I need to I can confine them and make sure they're safe. And, there's always the car. (My neighbor set her oven on fire this past summer, and put her dog in the car that was parked on the street, so he wouldn't run away or get hurt accidentally by the firemen.)
Personally, I don't like to think about these things, but I guess I should plan something.