The Sac Bee has an interesting article today on projections by the City and County of Sacramento of potential floods that might occur given different scenarios of failing levees. This article comes complete with maps of how deep you can expect the flood waters to reach in your area, as well as evacuation routes.
Of particular interest was this bit in the article:
Generally, you will not need to drive for hours to be safe if a levee fails. You only need to get to high ground. Good areas to aim for: Carmichael, Citrus Heights, Folsom, Davis and cities along the I-80 corridor such as Rocklin and Auburn. In general, going north on I-5 or Highway 99 is not advised because of low spots. Heading south on Highway 99 is also iffy because it can flood.
So basically, if you live south of Highway 50, you’re screwed.