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.
Mini Flashlight: These things are amazingly powerful and have great battery life. Plus, they are super cheap. Tuck two or three away in your carry-on. And throw in a head strap, too.
Head Lamps: Yes, this is a no-brainer, but don't forget backup lamps and lots of extra batteries. It can get dark down there.
Headlamp: Since building a fire for light will almost certainly be out of the question, bring along a headlamp with some extra batteries to light your way.