Upper Middle Boulder Creek between Boulder and Nederland, Colorado, is a fast and manky run. At medium flows this is a pretty stout run. At high flows it is insane, and at low it is much more manageable but bony as hell. Boat ripper. The mile above Boulder Falls (Boulder Falls is on the
North Fork Boulder Creek just above the confluence, there will be ton of tourists there) is pretty much one giant Class V+/VI rapid with every river hazard Colorado holds; wood, undercut, sieve and more!
Below the entrance of North Boulder Falls into Middle Boulder the streambed mellows out a bit to Class IV+ spiced with the occasional Class
V to V+.
Even this lower section is pretty much nuts at high water so usually we end up paddling it at low water when the holes are painless