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Thread: How much rain to fill a canyon?

  1. #1

    How much rain to fill a canyon?

    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.

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  4. #3
    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.


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  6. #4
    Content Provider Emeritus ratagonia's Avatar
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  8. #5
    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


    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

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  10. #6
    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.

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