Glen,
Bookstores like Borders and Barnes & Nobles carry maps like the "Virginia Atlas & Gazetteer." They are topographic maps that cover each area of the state in great detail. They also show the towns and highways along with the topography. I have used them a lot in tracing the routes of early Virginia explorers and in looking at Civil War troop movements. I am not sure you will find every river ford listed by name, but many are. The contour lines will give you the altitudes. If you can't find them where you live, you should be able to get one in Warrenton. The maps are published by DeLorme (web site: www.delorme.com (207-846-7000).
Hope this helps.
John