We get flooded here and threatened with bushfires. I ALWAYS have an 'evacuation kit' in the back of my car over summer. It has a weeks worth of food for the dog and chickens, an extra lead for the dog, a muzzle (he doesn't need it but if you need to evacuate by bus or on a boat they won't let your dog on if they're not muzzled, and leaving my dog IS NOT an option!!!), four litres of water, a change of clothes for me, a radio and woolen blankets.
I also have made crappy harness and leash sets for my hens. This is because when we had bushfires around here a while ago and I saw people staying in the town hall who had evacuated with their chickens by shoving as many as possible into cat carriers and boxes. It took DAYS before the birds could be let out because resources were so stretched, no enclosure etc.
I even saw someone driving down the street with their horses running alongside the car because they couldn't hire a float to evacuate them!
I too would shove all my birds into a cat carrier but with the harnesses I could let them out to at least clean the cat cage properly, but still have them controlled!