"blown out"

[bearsdenbill]

blown out is a term we always hear in the spring. but stream/river monitoring rates give us guage height and flow rate.

cu ft /sec on a med river compared to a large river - take the deerfield and the ct. river - show a big difference.. but fish can be caught on even the largest rivers. so why does it have such a negitive effect on med and sm rivers and streams? hydrodynamics and bernouli's equation must figure into it somewhere - but is it just what the fish are used too?

when the habitat is out of sync - is that what makes the river/stream unfishable?

[Mark Patenaude]

There is no simple answer to your question, but whether I'm right or wrong, here is my opinion, most of it based on my personal observations and what I've researched.

*The flows on a small stream are, in comparison, much less than that of a large river on a normal basis and when the flows come up the "percentage" of increase as compared to a large river is more (i.e. small river typical flow = 100 cfs/large river typical flow = 500 cfs///flows come up in small river come up 100 cfs to 200 = 100 % increase///flows in large river come up the same amount of 100 cfs to 600 cfs= 20% increase).

*There are fewer "refuge" areas for the trout to seek out in a smaller river when the flows come up. There are typically more and larger boulders and deeper bank cuts/areas for trout to hide in larger rivers until the flows return to normal. However, in both small and larger river, casting along the bank in the smoother water will prove to be very productive as well as in front of and behind instream obstructions. Just don't wade out too far, you'll get wet.

*The riparian zone on a small stream/river is much more narrow than that of a large river which is spread out deeper along the banks and has more of an impact on the insects.

*Larger river are typically deeper and handle the "silting in" effect of higher flows better than smaller water. Remember that the areas along the river bottom with the least amount of flow are right at the bottom due to the bottom structure disrupting the flows and slowing it down a great deal as compared to the flows that we see on top.

*Bernouli's Principal deals with positive and negative pressures of air in lifting an airplane wing and doesn't apply.

*Typical tail waters (like the Deerfield) see radical changes in flows on a regular basis and the streamside vegetation, including the trees has adapted to these conditions and will seldom result in "dead falls" and dead vegetation due to flooding and silting in.

*Smaller streams are typically more shallow than larger rivers and the amount of sunlight penetration is more. Once the bottom gets stirred up and the banks erode due to higher flows and the amount of in-stream organic material is greatly increased, the result is turbid looking water as a result of prolific growth of mold/slime/etc... that effects the normal instream vegetation and insect population which takes a long time to recover (i.e. delay in hatches timing or complete elimination of a particular hatch if the conditions are severe).

*The once nice thing about extreme flows on a small stream is that is changes the instream structure a lot of time and makes for an interesting trip the next time out. I regularly fish spring creeks in Wisconsin and it seems that every spring the stream I fish are structurally different from the year before due to the changes from the spring melt off. It never gets boring, thats for sure.

Mark