Stream channel modification [Archive] - Fly Fishing Forum

: Stream channel modification

03-23-2003, 06:20 AM
Does anyone have any experience with placing obstructions in a small stream to create a riffle pool effect? The stream was channeled many years ago to build sewer beds. It is about five feet wide and very straight, about a quarter mile long. The stream drains a pond which could support a good run of alewives if I can give them reliable access to it through this stream.

Because the stream is so straight and suffers from considerable sand and siltation problems there are several segments where the water is only a couple inches deep. By raising the water level just a couple inches in these spots reliable access could be provided for the alewives and a good population could be established (perhaps a run of a hundred thousand adults).

Does anyone have any experience with this sort of project, or know of any print or online sources.


03-23-2003, 06:52 AM
I don't, but I will help restore this access if I can when you are ready Tim.

I've read that channels should have a vee profile to allow maximum passage during varying flows.

Perhaps we could get someone from the aquarium or science museum to team up with?

03-23-2003, 07:33 AM

Many years ago I recall a book on river management which had a great section on improving stream flow and habitat for both fish and aquatic insects. A web based search along those lines may turn something up.

John Desjardins
03-23-2003, 09:22 AM
I've seen the use of creative obstructions in several streams, and over the years they do wonders for stream bottoms. Most of the projects I've seen were done by local TU chapters under the adopt a stream program. They'd be a good place to start the search. Also look at

03-23-2003, 09:30 AM
I have done these types of projects in the past and always felt a bit like a kid playing in mud puddles, not an unpleasant way to spend a bit of time.
There are several ways to make the little vee devices that create small plunge pools and riffles. I always was operating in areas that had plenty of woody debris so there was no need for the building of screen boxes to fill with rocks to accomplish these deflectors.
A small stream that hosted a spawning area for a resident cutthroat population was cleaned up by a middle school biology class as a project. The kids did a great job of cleaning out the litter from the stream but also created a denuded habitat without any breaks in the current. I took it upon my self to do something about it and was totaly amazed at how much positive influence one could have by the replacement of a few strategicly placed logs and sticks.
I'm sure there are books on the subject but my advice is just do it. Wander down there and try a little bit and see what it looks like as you add a few sticks and rocks.
Sounds like a great project its the little things that make the big things work.

03-23-2003, 10:19 AM
I did something very similar to what the kids did on your stream Moonlight. The place was a real stinkhole, full of tires and every other sort of debri. The stream bottom was covered in oily mud and rotting vegetation because of all the trash which reduced the stream flow. After I cleaned it out we had a good rain and it was amazing how quickly all the silt and mud flushed out of it, that was about four years ago. Since then the sand has shoaled up in a few midstream sections making it almost impassable for fish.

I was thinking along the same lines as you. That by building some obstructions coming off the bank about halfway out into the channel above the shoals the water would carve out a narrow channel and create a back eddy below the obstruction. This should force the washed out sand up along the bank behind the obstruction rather than in the middle of the channel. I love this stuff.