How much rain to fill a canyon?

[mcweyen]

Does anyone have a link or knowledge on how much rain it would take to fill up an "average" slot canyon. I'm not talking Buckskin Gulch (giant) or something really tiny like Zebra... just an average slot, say something like Neon. Would a tenth of an inch in the area do the job or are we talking more like half an inch?

Thanks in advance for any info.

[Rob L]

[Iceaxe]

Speaking as someone who has witnessed literally hundreds if not thousands of flash floods I can tell you it takes a pretty good dump to get a canyon rolling, but once it starts to roll it's all hell is braking lose....

....short answer is I don't think you and quantify a flash flood in something like a 10th inch of rain as there are just too many variables.

YMMV

[ratagonia]

How many angels can dance on the head of a pin?

[kiwi_outdoors]

do the math

get catchment area off Google Earth or a Topo; work out cross section width of a typical slot channel of interest, assume a rainfall rate, pick your flow depth or flow speed and the other resulting parameter

e.g.

Assumes steady state and zero absorption
rainfall	1	inch/hour
area	1	acres
area conversion factor	43560	sq ft per acre
volume per hour	3630	cu ft per hour
slot width	6	ft
flow speed	44	ft/sec
flow speed	30.00	mph
flow depth	14	ft

[stefan]

interesting question. i can give you one anecdote: in mindbender it took 20 minutes of strong rainfall (didn't estimate the amount) to have a flash flood barrel off the final falls of the canyon.