Wednesday, August 25, 2021

Paria River Flash Flood


    The Colorado Plateau sports a number of gorgeous sandstone canyons that are routinely to infrequently paddled - Cataract and Labryinth are runnable year round, while Muddy Creek, the San Rafael Black Boxes and the Virgin River system have semi-reliable snowmelt runoff or releases after good winters. Paddlers debate the merits of a predictable spring or fall scrape/walk/float down the Dirty Devil, or occasionally catch a few thousands cfs on a summer rain event. Some small drainages like Dark Canyon, Courthouse Wash, and Cottonwood Wash have been paddled, usually by locals. The Paria River, spanning terrain from Bryce Canyon to the head of the Grand Canyon, though gaged, produces exceptionally fleeting floods given the extent of its watershed.

A 2017 Sorbet Soiree on the Paria


                    And now, from 2021:







    I live between 4 and 5 hours drive from the Paria, but if I wait for a flood to show up on the gage the river is reduced to a trickle by the time I arrive. So, the two types of events that produce marginally predictable flows: summer monsoon rains and winter rain-on-snow, must be anticipated. This is a difficult, frustrating and time consuming process that I don't want to get into the weeds about here. Suffice to say, I've now made it work for 2 out of 4 attempts based in Durango.
     The first success came in the winter of 2017:

(click for old video from 2017)

with Flows ranging from 120 cfs (narrows) to 200 cfs (boulder gardens) to 300 cfs (exit)
My initial trip spanned Feb 10-12. Shown: three diurnal snowmelt pulses followed by rain-on snow

    In mid-August 2021, an active phase of the monsoon created an opportunity. Usually a single dose of rain is too difficult to predict with enough geographic accuracy to justify driving for 5 hours, but the Paria basin had gotten hit with three runoff-producing events in 24 hours and a fourth was on the way. With soils/sand/substrate likely saturated, Tom and I decided to gamble on a trip. We drove out as the fourth rain event was occurring, and it looked like only slightly promising accumulation compared to the prior events. 

    Boy were we surprised when we reached the put-in!
Fourth rain spike arrived around 9am Aug 19. The Paria had only been that high twice since 2014.

    We didn't see that the gage had spiked at over 3000 cfs until after we finished the run (data reporting lag), we only knew the last report was 800+ and rising, but clearly it was going to be high. We weren't quite on the peak, but damn close and rode high water the whole way to the first serious rapids near the end of the narrows around mile 25.

    How high? I went back through my footage from the 2017 winter run to compare water lines to this 2021 summer run, and here are some sketches from roughly the same positions:

Entering the Narrows
2017
2021

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Slideblock Arch
2017
2021

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mid-Narrows rockfall rapid
2017
2021

        These are all relatively wide parts of the narrows, and in the short slot sections I'd guess our 2021 flood had water 8-10+ ft higher than our 2017 run. Even at extreme flows, I anticipated the low river gradient would produce little more than boils and seams - cobble bar riffles in the narrows could be run on the inside of corners and the rockfall only occurred in wide parts of the narrows so holes could be dodged. I'd read reports of successful hardshell descents around 500 cfs, so how different could 800+ be? Well, even given that we were actually riding >2000 cfs, I was mostly right. About 99.9% right. However, one of the roughly 3 slot sections (all 6-10 ft wide) featured an eddyless and narrowing run-in that started with mild laterals but delivered us straight into a set of crashing waves that was downright terrifying (starts at 1:00 in the video below). 




    In retrospect, it was fortunate that we couldn't stop to scout because there was no time get frightened or psyched out... we were just in it and had to execute. A wave hit my face and gopro at video minute mark 1:18 and obscured the view, but there were another few crashing waves followed by a boof off the side of a large submerged boulder into a relatively placid mudpool.

  Here's POV video of the run:

(Click for Video)

    The first overwhelming part of this experience, for me, was the smell. The river emits a heavy odor of wet earth that just penetrates everything; it felt like it was accumulating in my lungs. As we worked our way down the braided approach to the narrows, dodging active log jams, we got our first doses of mud/sand/water droplets. A single drop in the eye was somewhat crippling, and we both came to the conclusion that a swim, or even flip, or even a crashing wave to the face, could be catastrophic. 



    The water was so thick with sediment that it behaved and looked and felt different even compared to other desert floods I've paddled. The San Rafael or LCR at high flows were nothing compared to this, though the lack of foam here that the LCR featured is still curious to me. The combination of both mud and sand made it difficult to grip my paddle shaft - I took to dipping my hand in the river and immediately shaking the sand (not mud) off, then using my muddy hand to wipe the sand off the shaft. Otherwise I had too shaky of a grip. Awful. At every stop I would have to shovel handfuls of sand, foam, sticks, needles and juniper berries out of my cockpit.


    The somewhat predictable nature of the cobble bar rapids in the narrows became routine - strong boils off the walls were at worst meddlesome for our downriver progress. 



    One of the river-running problems at low flow in 2017 was that eddies were mostly filled in with sand so eddy hopping was not entirely easy. In 2021, eddies were much more workable in the vicinity of rapids.

    Working through the Paria narrows, the river cuts progressively deeper into the massive sandstones, exposing more easily erodible units underneath. This has caused the tall sandstone walls to retreat away from the river, but at the same time allows large blocks from the cliffs above to fall into the river channel. This, in combination with the higher gradient (~80ft/mi), forms a 4 mile long crux section of III/IV or IV/V rapids, depending on flow. 


    The first set of rapids we encountered, bedrock ledge plus giant boulder affairs, were mostly flooded out wave trains (!), but due to time spent scouting and portaging the water was quickly draining out. Fortunately, at the crux boulder gardens towards the end the water had already dropped by 3'. We still portaged about 5 rapids overall.

recent high water mark visible on left boulder

    Part of our plan involved not spending time to set shuttle at Lee's Ferry, so before our hike out over Dominguez pass back towards HWY 89 we spent the night. Meaning we had no spare water to clean gear or ourselves until the next day...



    Seven hours out of the canyon, over the pass and down towards the highway the next day.





    Would I do it again? Hell no! I mean, maybe...

    If you made it this far and still thirst for muck, check out MC's post from their winter run in 2019. Small flow for the narrows but similar flows in the lower rapids, and they used real cameras.