I made it out to the Tully yesterday to chase the tricos around Rebers Bridge Rd. I had limited success as the same old story applies ("you should have been here last week..."
). At any rate, I moved farther downstream mid-morning and checked out the confluence of Cacoossing/Tully as well as ventured up Cacoosing. I spoke with a "local spin angler" who was miffed at the dam removal and how it ruined his honey hole. I tried to explain to him that in due time, the dam removal would be a good thing, as it would allow a constant flow of cold water into the Tully (it was coming in at 62 yesterday). We just simply need some high water events to let Mother Nature do her thing.
There is a tremendous of "silt" that came downstream as well as what remains in the area that was above the dam. Hopefully they can get in and stabilize the stream above where the dam was, as it's in a pretty precarious position as it currently sits. The "silt" isn't silt like you'd see in a limestone stream, but instead has lots of little pebbles in it. Nonetheless, it is still soft and you sink when walking in it. There are still wild browns in this stretch, that I can tell you!
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No more dam 👏
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The photos show a typical situation when a dam is removed where there is a deep accumulation of sediments. I've seen this pattern at various dam removal sites.
When the dam is removed, the water cuts down vertically through the sediment deposit. You get a channel that is pretty straight rather than meandering, because when the dam is removed, the erosive energy of the stream is directed vertically downward, rather than laterally.
The channel is incised into the sediment deposit, with the water confined by steep banks on both sides.
There is little development of pool habitat, because there aren't features present to cause pool formation.
After McCoy Dam was removed on Spring Creek, it looked very similar. That's a larger stream, and the sediment deposit was quite large, probably 10 feet thick near the dam. But the basic situation looks pretty similar.
In the early days of the dam removal movement, they just removed the dam and considered it done. But what often resulted was a nearly straight shallow channel with very little good fish habitat (pools and cover).
That is why they now typically do some structural habitat work, such as rock cross vanes. That adds considerable expense, but you get some fish habitat rather than a shallow featureless "ditch."
Some people think that you can pull a dam, and "Mother Nature" will create good fish habitat. But I've seen old splash dam and mill dam sites from the logging boom of the late 1800s, and most of the sediment deposit is still there and you still have a nearly straight channel that is wide and shallow and lacking in pool and cover habitat. That's after about 100 years.
I know of one such stretch that is about 1 mile long. The water quality is good and there are good numbers of wild trout in other sections of the stream where there is pool habitat. But that 1 mile stretch through the old sediment deposit from the former dam has only a few small trout.
