We (Alexandria, VA) are stuffing as much yard stuff as possible in the shed, including the big planters. I've trimmed back some of the shrubs by the house so they don't whip around and snap. Don't forget to secure your trashcan!
For people worried about whether they are in a flood plain, I found this website that will generate flood plain maps:
http://www.esri.com/hazards/makemap.html This site generates topo maps.
http://www.topozone.com/default.asp On the Washpost website, I've read that past hurricanes have flooded up to where the Pentagon is now, and onto the National Mall (that's the grassy area between the Washington Monument and Capitol building, for those who don't know that.)
Also, mudslides can block streams. Four Mile Run flooded during one hurricane.