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Sweep Boats on the Middle Fork Salmon River


In the heat of the summer,  when I’m not  in my drysuit teaching with Sierra Rescue, I spend a chunk of the summer months up on the Middle Fork of the Salmon River in Idaho. I’ve been guiding commercial whitewater trips for ECHO River Trips for the last 9 seasons. About 5 seasons ago I took over as the sweep boat driver.

Sweep  Boats are interesting crafts unique to the Salmon River. The constant gradient allows for this baggage barge of sorts to be propelled downstream. Controlled and steered only by two long sweep arms (think two big hockey sticks mounted to the bow and stern), the sweep boat builds momentum and uses the gradient to fall downstream. The mechanics of how they move is a topic of heated  debate, but it all boils down to momentum and a phenomenon known to the sweep-boatmen as ‘sweepage.’ A sweep boat gains sweepage  when the boat moves faster than the current floating it, and  has the ability to  track in and around the rapids.

This summer’s snowpack was below average  an early melt this spring left us with lots of  low-water manuevering and navigation. Over the last few years, driving sweep has really enhanced my ability to read water, as moves must be planned well in advance. As Dropping into Tappan Fallsthe snow melts and the water recedes from the spring peak, each week is different, and the Middle Fork goes from a powerful non-stop high-water freight train to a low-water boulder dodge. Somewhere in that run-off, there’s a water level window when piloting a  sweep boat is pure bliss. Outside that sweet spot, the job is still awesome, but a little more pushing and getting stuck on the low end, and a little more violent on the high end.

If the daily loading and unloading of an entire trip for 30 people at each camp isn’t enough to keep a sweep boat pilot busy, the sweep boat itself presents some new wrinkles from a swiftwater rescue standpoint. The first concept to understand is that the sweep boat is the gear boat and leaves camp before the other boats on the trip, and is therefore alone all day. You are your own safety. That being said, the first sweep boat specific nuance is stopping.  Once you get moving its hard to slow the sweep down, much less stop it. There are no brakes. Sure it can be done, but nowhere near as easily as a standard side oar raft. Getting back to and back on a sweep boat if one found themselves ejected is a tall order. I don’t recommend leaving the boat under any pretense until safely anchored to shore.




Secondly during low-water years like this summer, the sweeps get stuck quite often. Typically it requires little more than some strategic pushing and pulling and maybe deflating some air from on of the 6 chambers. Other times the ‘sticks’ are more aggressive. Earlier this season I  helped a sweep boat out of the chutes, a notoriously sticky low water spot. From shore we set a quick anchor and with the transport hitch, tensioned a line and used a vector pull to free the boat. I love it when I can use basic rope tools. Quick and simple.

Sweepboats are right up there with an inner tube as my favorite craft to navigate whitewater. They are amazingly responsive and it is  incredible to witness the  maneuvers that they can make with two big rudders. Next time you’re out on the Middle Fork, check them out, and talk to the pilots. Sweep boats have a storied history  among the early boaters of Idaho and specifically the Salmon River.  My commercial guiding season has come to a close and its time to get back in the drysuit. I’m looking forward to another great season of Swiftwater Rescue. Come out and train.

-ZB 8.2013