If you are high enough that they won't be swimming, put halters on them. Affix a water proof tag with your name address and phone number, or write it on the halter. Maybe even spray paint your phone number on them. If you have a barn, don't close them up. Open doors, gates, let them choose where they want to be. They will probably want to be in the open.
I lived in hurricane country, mine would go in the barn, but spent most of the storm out in the open. The worst injury any of them ever got was a swollen eye, like flying debris hit her in the head.