On the Iowa DNR website there are maps of all the streams including roads and such. Also I use a Delormes Iowa map book and a book called, Iowa Trout Streams by Jean Hughes. It is all you really need and it is well worth the money. It covers trout fishing in Iowa with maps, gear(all flyfishing), the 4 seasons, patterns, etc.
I would start with Iowa DNR site. Look on Amazon or online for Iowa flyfishing shops for the book. The book is very detailed and a cool addition to any fly fishing library.