Fred, I'm math challenged, but the insurance guys wouldn't offer flood insurance cheaply if the risk is high.
(I hung out with an insurance actuary one time, and talked stats. A reality check.)
I'm sure some areas near Sac. are pricey though. Down there, I would fear the Sac. river near capacity, then add a shaker.
You could just station one of those marine survival rafts on the roof.
Keep a back-up rod and stuff in it.