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Is there a max Discharge cf/sec that is safe for wading?


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#1 Guest_vdub_*

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Posted 01 August 2008 - 11:30 AM

I was looking at the USGS graphs for the rivers in the area, specifically the discharge one and was wondering if there is a "safe" zone or a "dangerous" zone in cubic feet per second that you should or should not be wading in? I'm new to these stats so I'm just learning how to interpret the info. Thanks.

#2 Guest_drewish_*

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Posted 01 August 2008 - 12:03 PM

It is really dependent on the location. Some places may have 1000 cfs and be safe while on another river it would be hazardous. Also, if you are more experienced, you can handle higher flows.

#3 Guest_ashtonmj_*

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Posted 01 August 2008 - 03:28 PM

As Drew said, discharge and the realized force of flow in a stream are totally dependent upon the local conditions. I'll give you three examples from streams that are in the same region. 1) I've snorkeled in 6-8,000 CFS but the river was 200 meter wide. 2) That said, a 50 m wide river at 1500 CFS had about the same flow (0.75 meter/second). 3) In a 20 m wide stream anything over 300-450 CFS was above "normal"; again the "flow" was similar. In smaller streams higher discharge is more unsafe. Look at the long term hydrograph for a site and see what looks natural, what the median or baseflow is, what the peaks and valleys are like. Try to get information about the width of stream and gradient.

#4 Guest_vdub_*

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Posted 01 August 2008 - 08:55 PM

Thanks for the info guys! I guess I didn't think about the width, as well as flow (force) being different than discharge. I did see the peaks and valleys in the chart, and they had little triangles that represented the median for that time of year. So I guess I'll go by that. I am still working on fully understanding the percentile thing shown on the website. :neutral:

#5 Guest_rjmtx_*

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Posted 03 August 2008 - 11:50 AM

If you get out and flows are too high, don't just give up and go home. If you search around you might find some sloughs or tributaries that are full of fish. It's also a good idea to wear a lifejacket when sampling raging waters.

#6 Guest_JohnO_*

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Posted 09 August 2008 - 10:29 PM

Greatest danger in going down in a fast stream isn't drowning, it's getting knocked unconscious when your head impacts a rock as you're being swept along. Then you drown.

I've seen the normally near dry creekbed that passes in front of my house flash flood. Just happened to be standing out there after a couple of days of showers, and I guess the hills let go when they got saturated. It wasn't one giant wave, it was a series of small waves, a minute or so apart, that just never died down. I saw a little wave sweep down the creek, well isn't that neat? Then, here came another one, and the water level rose a bit more and picked up a bit more speed. A minute later, here comes another one. Each successive wave was just a little larger than the previous one.

That creek went from a few inches of flow to three feet of raging water in about a half an hour. That's what makes flash floods so dangerous. They sneak up on you. It looks safe now, but it might not be in five minutes.

#7 Guest_edbihary_*

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Posted 12 August 2008 - 12:49 PM

So, in other words, it's velocity and depth. You might be able to wade ankle-deep in fast-moving water, but knee-deep at the same velocity will sweep you off your feet. You can wade chest-deep in slow-moving water without a problem. Reading USGS stream gage data on the internet doesn't mean much unless you know what typical flow rates/depths are at a given location. Depth data are not necessarily from the bottom, but an arbitrary datum, at a specific location. It may be quite different at the spot you enter. Flow rates mean nothing unless you know the stream width and depth. You can have dangerous fast riffles and easy slow pools in close proximity. If you know the water is higher than usual, there's a much better chance that it's unsafe. The converse is obviously true if the water is lower than usual. But nobody can give you any guarantees. You have to assess the situation yourself in the field, compared to your own capabilities (and your children's if you bring them), and decide what is safe or unsafe. Don't get in water you think is unsafe. Period. Moving water is much more powerful than you might think. And remember, children are smaller and lighter than adults. Water that may be perfectly safe for you may be deadly to your child. Don't let your child enter water that will be unsafe for the child, even if it seems safe for you. Always use your head!

#8 Guest_vdub_*

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Posted 12 August 2008 - 12:57 PM

Thanks everyone for your input. I experienced what some of you are talking about this past weekend. While wading, the wider portions of the river were not as forceful as where the water was squeezing between either the two banks that were narrower or brush piles or timber that narrow the width of the river. I could also tell by how tight your waders get around your legs :biggrin: This was my first time out wading by myself (I know, wading with a partner is always the best) and wanted to get some info. Thanks again.

#9 Guest_edbihary_*

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Posted 12 August 2008 - 01:41 PM

Thanks everyone for your input. I experienced what some of you are talking about this past weekend. While wading, the wider portions of the river were not as forceful as where the water was squeezing between either the two banks that were narrower or brush piles or timber that narrow the width of the river. I could also tell by how tight your waders get around your legs :biggrin: This was my first time out wading by myself (I know, wading with a partner is always the best) and wanted to get some info. Thanks again.

Update your profile with your location information. You might find some seining partners if we knew generally where you are. Then you won't have to go wading by yourself ;-)



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