First Aid Kit: Pick up a waterproof kit with all the essentials. They come ready made for all sorts of disasters.
Plastic Whistle: Again, signaling for help could be the difference between life or death. Have a plastic whistle at the ready.
Waders & Boots: You'll be trekking through water of varying levels, so have some waders and waterproof boots on hand. Waterproof socks are also great items.
Waterproof Box: Aside from food, this might be the most important. Have all your important documents in the box... deeds, insurance forms, ID, etc., as well as your phones, walkies, flares, and other survival necessities.
Toiletries: While brushing your teeth may be the last thing on your mind as you are trying to stay above water, you'll want to stay as sanitary as possible as floods can be cesspools of disease. Get a waterproof hygiene kit to fight of the germs.
Life Vests: Another important item that comes in many different forms. It's suggested you get the ones that have pockets and belts built in so you can store more safety items with you.
Quick Dam: While this only works with lower levels of water, it could buy you precious time in your house during an evacuation or when trying to fortify your place. Have several yards of it ready to go as soon as the emergency horns sound.
Radio: More storms could be coming and more dams could be breaking. You'll only know this if you have word from the outside world. Make sure your radio is waterproof, like this submarine radio, and pack extra batteries.