Send us a suggestion!

How to tell if a canyon has the potential to flash flood

Discussion in 'General Discussion' started by Helo-ops, Jan 18, 2021.

  1. Helo-ops

    Helo-ops

    Messages:
    53
    Likes:
    55
    Location:
    85022
    So we know all that canyons come in different lengths, widths and shapes. With that said are there any tell-tell signs that a particular canyon has a pertinacity to flash flood?? Should we stay out of all canyons if a storm is coming??
    Just pondering
    stefan likes this.
  2. Bootboy

    Bootboy Atwood Gear

    Messages:
    1,788
    Likes:
    2,235
    Location:
    Utah
    There a lot of things you can consider to complicate the risk assessment, but if it “tut tut, looks like rain” the decision is obvious. Be careful not to create and fall into a heuristic trap.

    Any “slot” big enough to actually be a slot can flash big enough to kill you. So what follows is more for trivia and exercises in imagination than it is a tool for risk assessment.

    So, to speak to some of these complicating factors...

    Familiarity with the surrounding terrain and topography helps give you the best idea for how quickly it could flash and for the potential volume.

    Being familiar with a canyon itself through previous experience and observation under safe conditions is the best way to imagine these things. If you take careful notes regarding flood debris in canyons, often above your head in trees, on ledges, and in boulder piles, you will quickly be sobered at the flash flood potential of just about any canyon.

    Again, I make these observations for fun, not for risk assessment purposes. Seeing the flood potential does not factor into risk assessment because you quickly learn that any canyon is a bad place to be when it’s raining.

    Probably a bit redundant, but you get my point.
  3. ratagonia

    ratagonia

    Messages:
    5,825
    Likes:
    7,333
    Location:
    Mount Carmel, Utah
    An important factor is how proficient your group is. If your group is small and efficient, you can move through danger zones much quicker. Slow beginner groups not so good. The group in Keyhole (4 rappels for them) was a large group of beginners with one rope. It did take a very unusual super-cell with a direct hit to get them, but they were essentially immobile in the canyon when the rain hit. Immobile as in, they had only one rope so they were moving at a snail's pace; large group; lacked appropriate equipment; very little competence. Those are all on the ingredient list of disaster cake - add thunderstorm and you get the disaster that took place.

    Tom
    stefan and Bootboy like this.
  4. ratagonia

    ratagonia

    Messages:
    5,825
    Likes:
    7,333
    Location:
    Mount Carmel, Utah
    Being familiar with the canyon is very important, but can also create one of the worst heuristic traps - hubris. Many canyons have only a short technical section of "flash flood danger", so knowing this, you could choose Canyon A over Canyon B. For instance, the Subway has short sections of narrow canyon between places where a safe zone can be reached. And we have videos of the canyon flashing big, from those safe zones...

    Mystery Canyon Zion has a small, wooded watershed, a fairly short section of technical narrows, and a friggin' earth-fill dam dividing the canyon into two zones. Still, one of our friends going solo got caught by a flash in the technical section, but got to a safe zone, leaving his rope (his only rope) hanging on the last rappel he had done. The rope survived intact so he was able to make it out.

    Tom
    stefan, Bootboy and Helo-ops like this.
  5. Canyonero

    Canyonero

    Messages:
    1,306
    Likes:
    1,491
    Having watched a few flash floods from a safe location, I've been impressed that there isn't much of a science to avoiding them. Some canyons are easier to escape from than others, of course, but the best way to avoid a flash flood completely is to stop canyoneering. I challenge you to find an experienced canyoneer who hasn't been in a canyon within 12 hours of the time it flashed. I'll bet that has happened to me half a dozen times.

    Reduce exposure. Canyoneer less. Move faster. Get up earlier. Remember the canyon will be there another day. Just because you got lucky last time doesn't mean it will happen again. etc.

    When you really know the canyons, you'll find a few you can do safely in a downpour. But they're few and far between.
    Yellow Dart, stefan and Helo-ops like this.
  6. Scott Patterson

    Scott Patterson

    Messages:
    1,495
    Likes:
    1,461
    This.

    Don't go into a slot canyon if it's going to rain (or with longer canyons if it has rained recently). It doesn't matter how fast you move, how well you know the canyon, or how experienced you are. It doesn't amke sense to do it.
    stefan and Helo-ops like this.
  7. stefan

    stefan wandering utahn

    Messages:
    72
    Likes:
    125
    i think it's helpful to be aware of how quickly a storm can roll in, rain, and cause a flash flood. just as an example, in the mind bender fork of robbers roost we saw a storm come in rapidly and downpour. from time of beginning rain to a flash flood launching off the exit falls of the slot was about 20 minutes.

    also some canyons that are fairly long can have localized storms upcanyon that cause flash floods that travel down to lower parts of the canyon where the weather may appear okay.
    Last edited: Jan 22, 2021
  8. ratagonia

    ratagonia

    Messages:
    5,825
    Likes:
    7,333
    Location:
    Mount Carmel, Utah
    The classic (extreme) example of this is the Black Hole of White Canyon. Storms over Natural Bridges NP in the evening have produced a flash flood in The Black Hole 12 hours later, 50 miles away.

    Tom
    stefan likes this.
  9. Scott Patterson

    Scott Patterson

    Messages:
    1,495
    Likes:
    1,461
    Buckskin Gulch, Chute of Muddy Creek, Black Boxes, and the Little Colorado River have all done that too. The headwaters to those canyons are a long way from the narrowest sections.

    A few years ago a flashflood in Buckskin Gulch hit campers at nighttime. It wasn't raining where they were, but several hours earlier heavy rains fell in the Bryce Canyon area which feeds the Buckskin. Luckily all seven survived.
    ratagonia and stefan like this.
  10. stefan

    stefan wandering utahn

    Messages:
    72
    Likes:
    125
    antelope canyon is another example. in the '97 flash flood the rain occurred 15 mi away
    ratagonia likes this.
  11. brokedownjeep

    brokedownjeep Incureable Adventurer

    Messages:
    24
    Likes:
    31
    Location:
    Midway, Utah
    There’s a really good video/podcast on canyoneering weather awareness by North Wash Outfitters. It’s about an hour long. I learned a lot.

    Lizard King, Jenny, stefan and 3 others like this.
  12. Yellow Dart

    Yellow Dart It's only hubris if I fail.

    Messages:
    410
    Likes:
    471
    Location:
    La Verkin
    It's only hubris if you fail. ^_^
Similar Threads: tell canyon
Forum Title Date
Archives - Yahoo Canyons Group The nature of sjhow don''t tell.....was undisclosed canyons Nov 1, 2012
Archives - Yahoo Canyons Group Glen Canyon Satellite Images 99->03 Mar 9, 2006
Trip Reports Can anybody tell the location of The Great Chamber? Nov 8, 2018
Tech Tips and Gear Garmin inReach, Spot X, etc - what is best satellite messenger? Sep 13, 2018
General Discussion Via Ferrata (Telluride) Jun 21, 2018
General Discussion New Weather Satellite Nov 19, 2016