Browns Canyon National Monument Rafting Trips: Half Day. Our Browns Canyon rafting trips are the most popular white water rafting tours in the country! Recently designated a national monument, this beloved section of the Arkansas river boasts 10 miles of class II-III+ whitewater rapids that really are great for your whole family. Join us for a half day rafting trip through Browns Canyon National Monument on the Arkansas River! This is our most popular rafting trip with breath taking canyon scenery and views of the Collegiate Peaks (some of the highest mountains in Colorado) This whitewater section is a great beginner/intermediate with consistent class III rapids to keep seasoned paddlers excited and not to scary for.