guesing width of small streams from maps

k-bob

k-bob

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I often try to guess the width of small streams from maps. Which of the tiny streams in this image might be the widest/have the greatest flow, and why? Often can't see them in satellite images through the trees thanks (image from backcountry navigator phone app)
 

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The expanse of land being drained is the best indicator, I think. Cannot evaluate your maps, though.
 
if drained land is important, number 4 might be smaller than 3, even though number 4 appears to have a deeper ravine... thanks
 
Well expanse of land probably determines the volume of water, but gradient will determine depth to a large extent. I'd guess knowing something about each factor would be helpful.
 
right I now look at gradient over half mi stretches I might fish. streams with say 5-6% grade over .5 mi more likely to have some pools. ones nearer to 10% have plunge pools maybe falls.
 
Nos. 1 and 2 look too small.

Both 3 and 4 look worth a try. I'd have trouble deciding between the two.

But I would probably choose 3. Larger watershed area, as already discussed. And longer stream channel length above the last road.
 
I have a general rule of thumb when looking for "fishable" trout streams in the mountains of PA. If the catchment is 4 square miles or more it is generally fishable with a fly rod. Less than 4 sq. miles and the stream channel is generally too narrow and the stream side vegetation too tight. There may be trout in the stream, but getting at them is too much trouble. Based on your map, I'd say #3 comes closest, but still doesn't satisfy my catchment criterion, being approximately 2.5 to 3 sq. miles.

 
I've looked at those streams on the map before! Never fished them though. I think stream width is a function of watershed size in combination with gradient. Steeper streams seem bigger than they actually are. I can think of several examples of streams that are small, but still plenty fishable when they're tumbling down a mountain...when they hit the valley floor and lose their gradient that same stream can look pretty dinky, overgrown, and unfishable.

Just based on the map (and not PFBC list info, access issues, etc) I like the look of 1 a lot, but would probably fish 3 and 4 first based on what I perceive to be a larger watershed, as the others have mentioned. They all have enough gradient.
 
How do you estimate the square mileage of the catchment?
 
Actually #3 is as deep as #4, the difference is #4 is steeper. They both start above 1600ft. and enter at approx enter the big creek at 800 ft.My guess is that # 3 is a bigger stream, but the difficulty of guessing from a map is that other factors contribute to stream size, such as aquifer and the size of springs and flow of springs that feed the 2 streams. Also from know the area, there may be AMD outflows there that could contribute water toany of the 4 streams making one bigger than an other.
Generally I go for streams that have longer flows and if there are tribs that enter I like to see that. Sometimes streams start out small and don't get any larger.
Gradient alone doesn't make 1 stream larger than an other.
 
Troutbert: To estimate the area of the catchment, locate on the map the high points between the watershed divides. Draw a polygon (in your head if necessary) from point to point and close the traverse (so to speak). Use K-bob's scale to estimate the lengths of the "legs" of the polygon. Multiply length of polygon by its width and you should come up with a rough estimate of the catchment size (area).

Most of us tend to use the term "watershed" when what we are describing is the "catchment". A "watershed" by definition is the boundary line surrounding a catchment. A "catchment" is the area of land contributing runoff to a stream (i.e., the area within a stream's watershed boundary).
 
http://pgcmaps.pa.gov/pgcpublicviewer/

The Game Commission's Mapping tool is very useful for estimating catchment size.
 
Each is a first order stream flowing within the ridge and valley province, so there is a chance that they are not perennial streams but rather seasonal. They are just a bit too far off the I-81 corridor to be within the anthracite zone, so mine drainage is unlikely to be a factor in steam discharge. Also, I think it's safe to say that limestone springs are not a significant factor at this location (Catawissa drainage).
 
From the satellite images on AcmeMapper it looks like there is a road running right along #3, Klingerman Run. I'd scratch that one.

Cranberry Run looks like real backcountry. It's likely to be real small though. It's only about 1 mile from the origin down to the road.
 
thanks, interesting discussion. tups' thoughts on /4 sq mi to fish with a fly/ seem like a good fit here. I have fished #3 klingermanns, but I think it is smaller stream than most guys want to brother with... but not by that much. it might have 60-70% of 4 sq mi catchment as tups notes...thanks again all.
 
TB: I believe that road along Klingermans Run may be a gated State Game Lands maintenance road (SGL 58). Because the drainage areas of these streams are so small they are likely all but dry in July and August most years. Still, wild trout do somehow survive drought conditions, so you never know. Fish and find out.
 
K-bob: so you're not sayin' whether or not you caught any trouts in Klingermanns? I suppose it may be impolitic to do so, given the zeitgeist of the forum. Still, I am curious to know after all this speculation. Is it a perennial stream (flowing year round)?
 
I did catch little brookies in klingermans but it was awfully small... people sometimes mention "jump across" brookie streams but klingermans may be "step across" maybe 6 ft average width... always the question of whether to move upstream, where these streams get steeper, but then they have even less water upstream...

if you put the names of several of these streams in the internet along with epcamr there is a good old report on them

that is the eastern Pennsylvania Coalition for abandoned mine reclamation

thanks for the remarks I was more interested in general comments on trying to choose streams from maps

 
This might be one of the most educational threads I've read on this forum in my time here. I unfortunately cannot any value to this discussion but I'm absorbing all I can. Great topic!
 
foxgap I think elevation is a big factor. we recently fished two nearby streams, the first one was more fun and had more fish. There are other differences but that first one had about 5-6% grade over .5 mi, second one had about half that much grade.
 
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