Instead of a sandbag in the toilet consider installing a sewer backflow valve on your sewage line *before* it enters your house. Your toilet isn't the only appliance susceptible to sewage backflow, any outlet on that line can erupt. Also a sandbag may sustain a certain pressure, but when under enough pressure you'll have a bad burp to deal with. We put in a backflow valve a couple years ago in the event of Green River Flooding (the sewage treatment plant is in nearby Renton, in the potential flood zone), it cost a couple hundred dollars for an experienced plumber. Peace of mind.

Animal evacuation and shelter is now part of the protocol for most local US disasters, decided after Katrina. In the Seattle area we have a good partnership with the Humane Society to operate pet shelters in close proximity to shelters for people - literally get off the bus, check in your pet to a shelter, then check into your own shelter. This affords the opportunity for owners to visit their pets, take them out for walks - their pets are cared for, so maybe they can settle down and get a night's sleep too. Its more comfortable than living in your car with your pets which is where many pet owners end up without a pet shelter. Its not too difficult to set up provided you have partners with an interest in pets and a willingness to plan to operate the shelter (volunteers and/or staff). There is also a provision for large stock shelters, ex. in the Kent Valley they were prepared to shelter livestock and other larger animals near the Enumclaw fairgrounds.

Plan, plan, plan. Good on ya for being prepared!