Pembina

For nearly 3 years I lived 150 miles south of the Pembina Gorge and was able to do the run about 15 time at flows ranging from 400 cfs to 12,000 cfs.

For experienced whitewater boaters, optimal flows for surfing low angle glass waves appear to be between 3,000-3,500  cfs. The local outfitters in Walhalla rent recreational boats to tourists to float the river at summer time flows, (below 1,000 cfs (?) ) when the river has a different character.

Above 5,000 cfs the Pembina Gorge rapids mostly wash out and it makes sense to go over to the Little Pembina for 12 miles of continous class 2-3+ boogie of a few hundred cfs in a mineature canyon. Sadly this enters the main Pembina just downstream of the primary rapids.

A shorter run of 3 1/4 miles that captures most of the rapids is possible if you take out at the Brick Mine Bridge. It is odd to take out midway down a long small class 2 rapid in North Dakota. However, it will save many miles of flatwater and make for a short shuttle.

There are more waves than the video link below shows, but it is hard to take out and set up tripod in most spots due to a tricky shore.

The river bottom is composed of heavy mud that is able to hold it's shape well enough to make up rapids. Mini-root cliff embankments block exit for long stretches of the river and make for a hidden peril to novice boaters. Finally, many beaches are actually quicksand. So maintain caution on this unique hazard.

https://youtu.be/kR4BsO2f2PA