South Boulder Creek - Upper South Boulder Creek



USB is a short class V wilderness run near Boulder infamous for its ability to destroy boaters.  For some local hair boaters, this is their backyard training run.  For others, it's a run they contemplate stepping up to from the comfort of their living room in the off season, only to be forgotten about while spending the spring running Clear Creek.  For most boaters, it's one they gawk at in the guide book on their way to run Brown's Canyon.

For me, it was a run I ignored for many years while I cut my teeth (fortunately not literally) on easier Front Range mank.  A desire to step it up, combined with a drought year not leaving a lot of other good options, found me trying to round up a small group of local hardman boaters to show me down.  A spring storm brought temperatures down into the 30s with a rain/snow mix. Bad weather, hangovers, and the temptation of doggie kindergarten almost shut down our trip.  But ultimately, poor sense prevailed and we rounded up the usual suspects. By the time I was airing out a 10 foot boof in RIMBY, I knew we'd all made the right decision.

Put-in at Pinecliffe and enjoy the extremely short warmup because the class V starts immediately at a railroad bridge with the rapid known as Trainspotting.  Trainspotting is the best chance to tuck your tail between your legs and walk back up to the car.  Despite some descriptions that claim Trainspotting is more akin to the boogie water, Trainspotting is actually representative of the major rapids on this run.  However, if you don't like the looks of it and are considering portaging, there's no point in heading further downstream.  The next major event is the Gash.  Most people in their right minds portage the Gash, especially after a famous local kayaker died in the dangerous sieve.  But kayakers, not always known for good judgment, run the Gash on occasion (this kayaker does not recommend it).  An eddy on river right behind a boulder starts an obvious portage line.  

Lumberyard immediately follows and although it can collect wood, it was clean and relatively straightforward when I ran it.  Not far downstream and immediately after a fun 5 foot ledge boof, a sizeable eddy on river right tucked behind a large boulder signals the start of S-turn.  S-turn deserves respect not only for the string of moves required to negotiate the drop, but also because it runs straight into LZ falls, a mandatory portage.  At low water there's a nasty pin rock in the last 3/4rds of S-turn that deserves attention.  LZ falls has been run by 3 people at high flows, but for most, it only takes a brief glance to call it a portage.  Don't miss the small eddy on river right before the drop.

The next section is collectively known as Grand Piton National Park.  The name is a nod to climbers in the area and to what will likely happen to your boat if you're not paddling on red alert.  Having a crew that knows the lines is the best way to handle this section.  Some bushwhacking along the shore could and should be done if nobody knows the lines, but this is a long section of steep class V strung together with some lines that definitely do not go.  I ran it on directions and by following the helmet in front of me.  I was told something about a "triple drop", but I went through about ten drops that could have fit that description.

The gradient slackens, a little bit, until RIMBY.  The entrance drop on RIMBY may be the best kept secret on the Front Range, offering an easy 10 foot boof.  A slight upslope at the lip provides a perfect kayak ski jump style launch pad.  The bottom half of RIMBY has a couple of slides into holes with more rock dodging to avoid getting pinned.  

If it hasn't ended you first, the run ends in Gross Reservoir.  Another .75 - 1 mile flatwater paddle out (depending on reservoir level) will deliver you to your car with a smile on your face.

I first ran it at about 270cfs, which seemed to be a good minimum flow.  350 cfs is likely the friendliest flow, and at >400 cfs it starts getting fast with more significant holes.  At high flows, USB is commonly known as Normandy Canyon - guess why.


Flow Information:

Much to the chagrin of many Grand County residents (and beyond), the Moffat Tunnel diverts water from the dewatered Fraser River to the thirsty Front Range.  Flows from the tunnel can make significant contributions to the flow on this run.  The gauge data is located here:


Class V+
Current Flow 303.0 CFS
06-26-2019 07:45
Recommended Flow Minimum: 250.0
Average: 400.0
Maximum: 800.0
Typical Season Begins: April
Ends: July
Recommended Use Kayaking: Yes
Rafting: No
Canoeing: No
Packrafting: No
Fishing: No
Length Mile(s)
Gradient FPM


06-10-2012 - The bottom half of S-turn

Photo By: Bridger Steele

Subject: Kevin Cripps