This semester I am teaching a class on fluvial (river) processes that encompasses aspects of both hydrology and geomorphology. One of my goals is to take my students to as many of sizes and shapes of river as possible over the course of the semester. Usually, we go on one Saturday field trip that lets us experience a mountain river, but this year, scheduling conflicts made that virtually impossible. Instead, we took a lecture + lab period, stayed a little closer to home, and viscerally experienced a totally unnnatural mountain river at the US National Whitewater Center.
First view of the whitewater channel. Downstream of the bridge, note the supercritical flow, hydraulic jump, and downstream standing waves. These are features of mountain channels not frequently seen in lowland streams.
Basically, the whitewater contains two channels filled with rapids that empty into a big pool. Water is pumped from the pool at the bottom back up to the pool at the top and the raft (and the people on the raft) get pulled back to the top on a big conveyor belt. When no one is rafting or kayaking, the pumps are turned off and all of the water drains to the bottom pool. You can see that lower pool in the background of the top photo.
Going down the channel there’s a series of rapids that look something like this. Sometimes bigger, sometimes tighter, and sometimes at a curvy point in the channel.
The smooth tongue of water pouring over the drop just to the left of the channel centerline is supercritical flow, and the whitewater at the base is the hydraulic jump where flow becomes subcritical again.
The facility was built for a mix of casual visitors who pay for a guide to take them on a 90 minute raft ride and serious kayakers training for international competition. The Olympic whitewater kayaking trials were held here in 2008. The poles hanging from wires in the photos above can be moved around to set different courses for the kayakers. So the channel was designed to allow each rapid to run in ways ranging from mildly exciting to likely to catapult you out of your raft.
Looking up the channel.There are multiple lines to run in these rapids, some harder than others
The guides do a good job of tailoring the experience to the level desired by the people in their raft. Our group divided into two raft. One filled with students who wanted to go wild, and they did, all ending up out of the raft at least once during the trip. Most of the students in the other raft had never been on whitewater before so decided to start a bit milder, but we still had our excitement by the end. And I don’t think I’ll ever forget the look on my grad student’s face as she tried to haul me back into raft after I got thrown out surfing a rapid and came up on the other side of the boat. I think she was far more terrified than I was – she might need a new thesis advisor!
After our raft trip was over we had some time to explore the other adventures to be had at the Whitewater Center. There’s flatwater kayaking, mountain biking, climbing walls, ziplines, and places just to relax and watch the water. I took the following video of some other rafters going down the rapids pictured above. I’ll note that they all seem to manage to stay in their boats.
Fun! With a side dose of education. That sentiment seems to be the consensus on the student evaluations I gave out last week — the whitewater trip has been a highlight of the semester.
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