Pretentious Snobby Bastard Fly Fishing!

Fly Fishing Reports => Local Trip Reports => Topic started by: trout_boyII on December 17, 2008, 08:27:43 AM

Title: Max cfs for wading?
Post by: trout_boyII on December 17, 2008, 08:27:43 AM
It's been so long since this was an issue, I've forgotten common sense estimates for limitations on wading at higher cfs.  What limits do you use generally?

TB
Title: Re: Max cfs for wading?
Post by: flatlander on December 17, 2008, 08:31:57 AM
Isn't that wholly dependent on the river? Not sure you can apply a general rule of thumb to it.
Title: Re: Max cfs for wading?
Post by: trout_boyII on December 17, 2008, 08:37:38 AM
I agree, so let's pick the Davidson as an example.  Feel free to add your own examples.

TB
Title: Re: Max cfs for wading?
Post by: Woolly Bugger on December 17, 2008, 08:45:39 AM
Yeah, it's all relative to the stream... I think the key is getting to know a river and checking the flow when you are there then you can make direct comparisons.
Title: Re: Max cfs for wading?
Post by: troutphisher on December 17, 2008, 08:57:02 AM
Deuce

You can fish the Davidson at 1000 cfs, don't worry jump right in....... 0--0

Remember to enter the stream at the  narrow section to get the full efect.... ;hb
Title: Re: Max cfs for wading?
Post by: Woolly Bugger on December 17, 2008, 09:01:55 AM
Here's my example for the Davidson...
Title: Re: Max cfs for wading?
Post by: trout_boyII on December 17, 2008, 09:05:07 AM
Quote from: troutphisher on December 17, 2008, 08:57:02 AM
Deuce

You can fish the Davidson at 1000 cfs, don't worry jump right in....... 0--0

Remember to enter the stream at the  narrow section to get the full efect.... ;hb


Thanks for the vote of confidence TP!  I'll have to give that a try.

TB
Title: Re: Max cfs for wading?
Post by: troutphisher on December 17, 2008, 09:40:39 AM
Deuce,

Another trick you can employ, is to only stand on one foot. This decreases  the surface area on witch the force of the water can act upon. It's like cheating physics!

A simple calculation shows that P is a product of F/A, so by reducing A, you also reduce P.

P= Pressure

F=Force

A= Area

Trust me it works....... 0--0

If your still not convince, you can tackle the raging river on one of these.

http://www.youtube.com/watch?v=kNXdK4-hJmk (http://www.youtube.com/watch?v=kNXdK4-hJmk)

Title: Re: Max cfs for wading?
Post by: glassfisher on December 17, 2008, 22:13:58 PM
I waded some steelhead streams up north in the 600-900 CFS range, it can be really tough in areas with big rocks.  The only thing you can depend on is <200 is ok, 200-800 depends on the river, >800 is a gamble.   :o
Title: Re: Max cfs for wading?
Post by: Mstash on December 18, 2008, 05:09:36 AM
I follow 5X
Title: Re: Max cfs for wading?
Post by: trout_boyII on December 18, 2008, 08:12:55 AM
After all the wonderful helpful suggestions on this thread, I decided to test my own theory that 200+/- on the D was OK, I hit the river about noon yesterday with cfs at about 220.  Following TP's suggestions, I dropped in at narrow section near the hatchery.  Sorry TP, it obviously wasn't running 1000 cfs, but I did find the nooses you so thoughtfully left for me handy in pulling rhodo limbs down to retrieve snags.    :-*

While the water was quick and I'm sore today from moving around in it (I'm old you see), it was doable.  Fishing?  Yes.  Catching?  Not so much.  Tough to get the fly down at this velocity and mending was tough.  Probably should have opted for bugger down stream.   o-o

Later I went downstream, assuming that wider would slow speed down.  (P = F/A ?) It didn't really make that much difference except in significantly deeper sections.  This was before the Looking Glass confluence so there was no additional water being added.  I'm not questioning the formula - too many other factors (streams other than Looking Glass, elevation drop, etc. plus I was estimating which is notoriously inaccurate - just look at my claims for length of fish caught!  ;D  Not rocket science revelations for sure, but it has been a while since I've had to even think about it, so an interesting day to say the least.  In any event, it should give someone pause when jumping into these conditions.

Thanks for your suggestions all and I'm thinking about checking into a river board.  Wonder how you would mend on that thing...

TB
Title: Re: Max cfs for wading?
Post by: Bloy on December 18, 2008, 21:11:15 PM
I'll go with Wolly's info. It's more high tech  8)

Barry
Title: Re: Max cfs for wading?
Post by: 5xTippett on December 18, 2008, 23:33:28 PM
Look at it this way.  If you are fishing the Davidson and get knocked off your feet, you won't get far.  You will end up wedged between all of those comatose people who cast to the same fish for days on end without ever moving.  You can drag yourself to shore from person to person until you get to the parking lot.  Mstash, despite what some people might think, neither one of us is stupid.  If we got out of the car and saw a raging torrent, I think we'd probably keep going upstream until it was wadeable! :)  Or possibly even try somewhere else, like the SoHo for instance. ( I haven't talked to Riverman in a couple of days, but I think he still likes us.)
Title: Re: Max cfs for wading?
Post by: trout_boyII on December 19, 2008, 08:18:17 AM
You have a valid point 5x.  I've always wondered about the stand in one place and slap the water approach.  I enjoy "wading" as opposed to standing in the D.  I doubt I catch as big a fish (actually, I know that I don't catch as big a fish), but the river is beautiful in most places and there are pieces of it that rarely see folks unless they look.  I really enjoy how different parts of the river look and fish differently.  Gotta hike some, but I suppose that's normal.

If you want to hang out at the bridge , fine - done it myself - but the D has much to offer upstream and down stream if you want to look for it.  Having said that, I hope you all hang out around the hatchery!  ;D

TB

Title: Re: Max cfs for wading?
Post by: wvyou on December 19, 2008, 14:10:26 PM
After a close call on the Raven Fork last weekend, I'm taking the better safe than sorry approach.  If you don't drown,  plan on the water temps killing you.
Title: Re: Max cfs for wading?
Post by: fleming13 on December 27, 2008, 20:29:07 PM
Quote from: wvyou on December 19, 2008, 14:10:26 PM
After a close call on the Raven Fork last weekend, I'm taking the better safe than sorry approach.  If you don't drown,  plan on the water temps killing you.

I would not want to be caught up in the park with the water coming up.  Any stream that can put big hemlocks on top of SUV size boulders is scary!  Now with the water normal.... ;D
Title: Re: Max cfs for wading?
Post by: TROUTMASTER3000 on January 05, 2009, 13:54:27 PM
Just wear a belt.  Its fun to then jump in to a big plunge pool at the end of the day (In the summer to cool off).  Plus your waders keep the air in them and its hilarious, sometimes they float and you are floating upside down!  Its great to take underwater pictures!
Title: Re: Max cfs for wading?
Post by: Silver Creek on February 02, 2009, 18:56:10 PM
Quote from: troutphisher on December 17, 2008, 09:40:39 AM
Deuce,

Another trick you can employ, is to only stand on one foot. This decreases the surface area on witch the force of the water can act upon. It's like cheating physics!

A simple calculation shows that P is a product of F/A, so by reducing A, you also reduce P.

P= Pressure

F=Force

A= Area


Unless I am misinterpreting what you are saying, I've got to respectfully disagree for fast water. I believe having only one foot on the river bottom is generally less safe than having two.

Your formulas are correct but I think you have applied them incorrectly. P (pressure) is force per unit area and is not the most important factor. The physical property holding to the bottom is actual Force (body weight) acting through friction between your feet and the river bottom. Pressure is how that force is distributed, and not the force itself.

I think you are confusing the force pushing you down the river vs the force holding you to the bottom.

The force pushing you downriver is not related to the area that your foot has on the bottom of the river but the total body area in cross section to the direction of the flow of the river. Standing sideways to the flow is the way to minimize cross sectional area and reduce the total force pushing you downstream. The PSI or pressure per area actually stays same, but you decrease the total force by minimizing the area.

The force holding you to the river bottom is your body weight. Lifting up one foot will shift some additional force or your weight to the remaining foot. So the pressure per area increases but the total force does not and most of the time actually decreases. How does this happen? By lifting up one foot, your center of gravity shifts. To compensate in fast flows, you need to lean more forward into the river flow to remain in balance. When you lift up one foot, your center of gravity is no longer centered over your remaining foot so you actually have less total weight on that single foot than you had on both. The vector force of your weight centered over your remaining foot is less than your total weight or force when centered over both your feet.

That is why a wading staff helps. When you use a wading staff, it is possible to keep your weight centered over the staff and remaining foot even with one foot off the river bottom.

Stand sideways to the river flow and use a wading staff. Keeping both feet on the river bottom or a staff and one foot keeps your weight centered over the attachment points. Always cross the river below a deep section rather than above.
Title: Re: Max cfs for wading?
Post by: troutphisher on February 02, 2009, 19:25:19 PM
LOL....you missed the jest of it.

But since you brought pressure, I think you misunderstood. The pressure you are referring to, is a result of the persons weight. That weight in-turn acts upon   the surface area of the person shoe print or sole size, as is not necessarily an even distribution. It also greatly depends on the surface of the sole, what is the coefficient of friction, since it is friction and pressure holding the foot firm. Another way to look at this as an example would be to study the fiction between a hard rubber sole and the felt sole. Felt has the ability to grip based on the long fibers of the felt and rubber has a much smoother surface, resulting in lower coefficient, thus would slip more if a force acting on it was perpendicular to the friction surface.

Pressure is a result of force, and the unit in this case is area. If the person wading had fat chubby legs, it is entirely possible, that the surface area and resulting force, would overcome the friction and pressure of the sole resting on freestone rocks. And it that case, reducing the surface area subjected to the force, in this case water flowing against the leg area, one could reduce the resulting pressure, by reducing the exposed area.

It is a balancing or equilibrium of these pressures, based on coefficient of friction, water flow in cfs, and weather your a fucking fat ass or not, that determines weather you are stand against the force on one leg, or take a drink.

of course assuming the force vectors are perpendicular witch results in higher values.
Title: Re: Max cfs for wading?
Post by: fishhunterphil on September 12, 2009, 19:11:47 PM
Quote from: troutphisher on February 02, 2009, 19:25:19 PM
LOL....you missed the jest of it.

But since you brought pressure, I think you misunderstood. The pressure you are referring to, is a result of the persons weight. That weight in-turn acts upon   the surface area of the person shoe print or sole size, as is not necessarily an even distribution. It also greatly depends on the surface of the sole, what is the coefficient of friction, since it is friction and pressure holding the foot firm. Another way to look at this as an example would be to study the fiction between a hard rubber sole and the felt sole. Felt has the ability to grip based on the long fibers of the felt and rubber has a much smoother surface, resulting in lower coefficient, thus would slip more if a force acting on it was perpendicular to the friction surface.

Pressure is a result of force, and the unit in this case is area. If the person wading had fat chubby legs, it is entirely possible, that the surface area and resulting force, would overcome the friction and pressure of the sole resting on freestone rocks. And it that case, reducing the surface area subjected to the force, in this case water flowing against the leg area, one could reduce the resulting pressure, by reducing the exposed area.

It is a balancing or equilibrium of these pressures, based on coefficient of friction, water flow in cfs, and weather your a fucking fat ass or not, that determines weather you are stand against the force on one leg, or take a drink.

of course assuming the force vectors are perpendicular witch results in higher values.

Epic, applaud worthy, response.


Title: Re: Max cfs for wading?
Post by: overbrook on January 01, 2010, 21:40:00 PM
The Congaree....

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Title: Re: Max cfs for wading?
Post by: DCBuckeyeguy77 on March 29, 2010, 21:55:58 PM
Quote from: wvyou on December 19, 2008, 14:10:26 PM
After a close call on the Raven Fork last weekend, I'm taking the better safe than sorry approach.  If you don't drown,  plan on the water temps killing you.

I gotta say that Raven's Fork is one of the last places that you want to get caught at when its rainy. I believe that it's one of the fastest rising rivers in the park... and out of the park.
Title: Re: Max cfs for wading?
Post by: hillbilly327 on July 07, 2010, 18:10:17 PM
Generation schedules on Tailwaters are a good guide for safe wading.  CFS means little if you do not know the stream.  1000 cfs is a flood on a small stream and a drought on a large stream.  200 cfs will have an average instantaneus depth for a linear foot of water of 2 ft on a 100' wide stream and 20' on a 10' wide stream.

I will opine on 3 rivers that I wade and hopefully others can fill in the more information on other tailwaters so that we can create a safe wading guide (all streams will have deep holes and drop-offs even in drought conditions):

SoHo--easy to wade with no generation and hard to impossible when generating.  Because of the Wier, it appears that the water has a slow rise until the wier is full and a quick drop after the wier overflow stops--very nice.
Hiwassee--easy to wade with no generation, difficult but wadeable on one generator, unsafe to wade with two generators.  Water takes about 30 minutes to get about 2 miles and rises fairly fast.  Our rule is reel in and walk off the river as soon as the water starts rising if your are in the first mile or so from the power house.
Blue Ridge--easy to wade with just the by-pass generator and impossible when generating.  River takes about 4 hours to rise as far down as Curtis Swich.  It comes up dangerously quickly if you are near the dam and the high, muddy, banks--stay alert.
Clinch ?
Watuga?
others ?

Please add your observations.
Title: Re: Max cfs for wading?
Post by: Jeffrey7302 on August 09, 2013, 22:52:09 PM
Folks, I am new to fly fishing, but am an experienced angler and an environmental scientist, and you need to appreciate how streamflow is computed. It's the cross-sectional area at any particular stream location, generally a sum of polygon approximations, multiplied by the avg stream velocity. This means that you could have a very big river, but with a low current, and still compute a huge cfs. But, as long as the depth is wadable, that flow is not gonna be a problem. Or, you could have a small mountain stream with a really fast current w/whitewater, that, because of the small cross sectional area, will compute as a low cfs, but which could easily knock you down.


So, it's really the stream velocity that you want to focus on. You can back this out of the cfs by estimating the cross sectional area, in square feet, and dividing the cfs by this area,

As to what's a safe velocity, off the top of my head I'd say anything within about six fps of current, which is about 4 mph. A more experienced wader could no doubt handle more.

Of course, the water depth is important too. It's one thing fighting a 4 mph current thats around your shins, and quite another when its up to your waist.