Kelly’s Whitewater Park is located in Cascade, Idaho, about an hour and a half north of Boise. It has a long flow window thanks to Idaho Power and the dam just a mile upstream. It sports a fast, green wave in the whitewater park, and with flows between 3,000 and 4,000 cfs you’ll enjoy a fast wave with solid green shoulders.
Kelly’s has a Webcam, which gives a great idea of what’s going on at the wave.
The North Fork of the Payette at Cascade gives an accurate flow. Look for flows over 2,000 cfs, and between 3,000 and 4,000 is a prime window.
The park has a fair amount of dedicated parking. Just look for parking near the visitor’s center.