CFS

[mtn_dude]

I had someone ask me what the ideal CFS would be for canyoneering, not in slot canyons, and I didn't know how to respond. I've never really done any class C canyons. Thoughts?

[Brian in SLC]

Really depends on the geometry of the canyon.

[Iceaxe]

What Brian said....

50 CFS in the Zion Narrows is great for little kids to go wading. 50 CFS in Kolob is deadly.

[ratagonia]

You mean, the optimum flow? as measured in Cubic Feet per Second?

Entirely depends on the canyon. Some canyons are rowdy at 5 cfs, some are barely getting going at 50.

Tom

[Bo_Beck]

The Zion Narrows was ok at 220cfs, but would have been fine at 300-350 in my Duckie done from 4 miles up Deep Creek and down to Temple of Sinawava.

San Juan River at 300cfs was boney, but was pleasant at 1000cfs!

Escalante River was boney at 60cfs, but became pleasant at 120cfs in an Alpacka Packraft.

Cataract Canyon was just perfect at 7000cfs in an Alpacka Packraft!

I'm hoping The Grand Canyon is running 12,000-18,000cfs when I row it my first time this march in a 14' cataraft!

Kolob Creek my first time at 15cfs was fun but testy, at 5-8cfs is a blast, at <5cfs is fun and quite mellow!

[penmartens]

Lower Black Box at 50 cfs without a life jacket-spicy.

[mtn_dude]

Yeah in my first bit of looking around I saw where someone said Kolob Creek should be about 8 cvs for the best. What about the canyons in California? More open so the cfs can be higher and remain safe?

[Bootboy]

Upper Kolob is not recommended above 3cfs, 5 is the absolute limit. The lower canyon picks up water at oak creek and may end up around 8. But 8 cfs in the technical portion would be really hairy.

[ratagonia]

Upper Kolob is not recommended above 3cfs, 5 is the absolute limit. The lower canyon picks up water at oak creek and may end up around 8. But 8 cfs in the technical portion would be really hairy.

Except that...

They set the gate at the dam, usually at "3-5 cfs", but it is set 'by eye', so will vary quite a bit.

One time we went in there and it was more rowdy, fun but a little scary, and I called that "8cfs". But I cannot say my eye for water is exactly calibrated, it was just considerably more than what was called 3-5 cfs last time I was through.

Zion NP will not issue a permit if WCWCD tells them they are releasing more than 5...

Summary: when people say how much water is in there, especially me, they are just pulling a number out of the nether regions - don't take the NUMBER too seriously.

Tom

[ratagonia]

Yeah in my first bit of looking around I saw where someone said Kolob Creek should be about 8 cvs for the best. What about the canyons in California? More open so the cfs can be higher and remain safe?

Again, each canyon is different. Your question cannot be answered in a general sense.

Tom

[sonnylawrence]

Again, each canyon is different. Your question cannot be answered in a general sense.

Tom

Well maybe yes or maybe no. I think it depends....on the equipment at hand. I had dinner once with Chris Brennen, the retired Caltech fluids dynamics professor who has the great canyon beta on California. We discussed this problem. My goal was to have a simple measuring "tool" that could give me a Go/No Go answer to the question: can I rappel and be able to handle the force of the water that would be hitting me? I wanted that "tool" to be made of a piece of gear a typical canyoneer would have in his/her pack. In some ways the problem is initially simple but becomes more complex. It is not just the number of cfs of water flowing down the drop. That can be fairly easily determined, especially at a constricture. You also have to consider the volume it is contained in. Easy to rap in very aerated water. More difficult if the air is squeezed out and it is solid water hitting you. So you are attempting to eyeball two things: the cfs and the volume of canyon that water is running through at the location your body would be standing. How many cfs are actually hitting you? Do you have fat or skinny legs? Laying on your side? It gets more complex as you descend and the shape (hence volume) of the canyon changes. The actual cfs may or may not change. And of course things change as the angle of the drop changes.

So I wanted a meter, a device I could lower into the waterfall first, get my value. Then decide if I should go or not. Of course I would need prior experience to know what the value is that I could safely descend. My class C rappelling skill would have to be calibrated. There are certainly expensive and heavy devices that scientists use that could accomplish this. But we (mostly Chris) could not decide on how to simply build one with standard canyoneering equipment.

Hence I am left agreeing with Tom that in a "general sense" the question can not be answered even though I know a good scientist could answer it.

[Brian in SLC]

CFS Canyon Poodle!



Really a hard thing to eyeball especially with the limited amount of viewage you get in a canyon.

Its all good 'til it ain't...

[DOSS]

So I don't think you want to measure CFS as that obviously is not a number that works in all situations. How about some tool to measure pressure of water on a given area. Say something like a underwater parachute hooked up to a scale on a bit of rope? this way you could get pressure that the water flow is exerting on a known area.. a little math and a table to show Go/No Go... I don't know just throwing it out there

[sonnylawrence]

..something like a underwater parachute...

Oh boy. Hope you don't design aircraft!
What you describe matches the discussion Chris and I had. You are correct, it is not really the CFS. What is important is the force of water that will actually hit you. So what common piece of canyon gear could be rigged into a meter, sent to the worse part of the flow, activated, then retrieved once the Go/No Go decision was made?

[DOSS]

Oh boy. Hope you don't design aircraft!
What you describe matches the discussion Chris and I had. You are correct, it is not really the CFS. What is important is the force of water that will actually hit you. So what common piece of canyon gear could be rigged into a meter, sent to the worse part of the flow, activated, then retrieved once the Go/No Go decision was made?

Sorry I guess I should have said "sea anchor".. how about a empty try bag with the mouth held open hooked onto some bungee cord... X amount of stretch on the cord could be pre measured to determine PSI and go from there..

[dweaver2130]

During basic swift-water survival training I received in the academy they told me, if you have to second guess or discuss if the water is moving too fast, the answer is probably that it is. I know we see fast water in canyons from time to time, depending on the canyon, but maybe this line of thought can be applied here.