The Ice Age Flood Tour, Portland to Prosser, Grand Coulee and Back, Yakima River Valley Formations was written as an addendum to the Tenth Edition of the book. In response to the questions raised by some of my friends, the book highlights the formations of the flood that are unique to the Yakima River Valley. Many of the formations are also covered by the Prosser Scablands Tour in Segment 3 of Tenth Edition.