Dredging effect on the environment?

[Wilderness medic]

Normally I hate laws restricting freedoms but I cant say I've ever been bummed about dredging being banned in California. I feel like its gotta do some serious bad things to out waterways, especially when its already so low with fish dying off and unable to spawn as easy.

But I really don't know anything about it other than an uneducated guess. Does it screw up the environment? I always feel like I'm jacking up waterways just be using my sluice and choking out all the water dwelling creatures downstream. I would assume rearranging massive piles of riverbeds can't be good.

Educated me?

 

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[Back-of-the-boat]

When dredging you are removing lead,old iron nails and such and also mercury covered gold, pretty sure removing heavy metals out of a river is a good thing, not bad, and stirring up the bottom which holds nutrients, the fish downstream will eat is a benefit to the environment.

 

[smokeythecat]

Dredging? Dredging out of the creek or river bottom, no harm. Digging into banks, not so cool. But I tell you, we've had quite a few floods and some flash floods here this year that have (each one) done more damage to the creek than you could do in 100 years with a dredge. It was so violent it threw black sands containing gold 5' out of the creek bed onto my lawn.

 

[Capt Nemo]

It will help break up the cemented cobbles and allow both fish and insects a place to breed and live.

Here's what can happen when do-gooders play with a stream. One stream that I used to go as a child was hit by such folk. The stream was wide and shallow with a sand and rock bottom. Wading, you could see many crayfish poking out of the rocks, trout, minnows, shiners, and suckers, and the bottom around the rocks was somewhat yielding. We'd catch a bucket of good sized crayfish every year, and so would others, and yet the stream had no problem sustaining the take. Underneath the rocks you'd see freshwater sponge and lots of insect larvae along with a whole lot of our target crayfish. It stayed that way for 40 years. Then came the DNR. They killed off the crayfish and rebuilt the stream to make blue ribbon trout habitat. Now the stream is narrow and deep. You see almost no crayfish, or very little else in the river, and the bottom has become firm and unyielding. And there's NO TROUT! The crayfish were keeping the rocks loose by burrowing under them, and in turn allowing the fish to spawn and insects to thrive.

Our dredging does the same things that the crayfish did in that river.

 

[Bejay]

I can post the complete study but it shows no harm done by suction dredging. Other factors may lead to destruction of habitat and stream dynamics but it can not be attributed to dredging. Per all the studies that have been done.


1999 EPA Suction Dredge Study On the Fortymile River, Resurrection Creek, and Chatanika River, Alaska
Courtesy of Alaska Mining & Diving Supply.
(Visit their section on Suction Dredging & The Environment for related information.)
For a copy of the report, contact:
US EPA Region 10 Library
1200 6th Avenue OMP-104
Seattle, WA 98101
Phone: 206-553-1289
Impact of suction dredging on water quality, benthic habitat, and biota in the Fortymile River, Resurrection Creek, and Chatanika River, Alaska
Prepared For:
US Environmental Protection Agency
Region 10
Seattle, Washington
Prepared By:
Aaron M. Prussian, Todd V. Royer, and G. Wayne Minshall
Department of Biological Sciences
Idaho State University
Pocatello, Idaho
FINAL REPORT
June 1999
Table of Contents
Summary
Part I - Suction Dredging in the Fortymile River
Introduction
Methods
Results
Discussion
Part II - Recreational Dredging in Resurrection Creek
Introduction
Methods
Results and Discussion
Acknowledgments
Literature Cited
-----------------------------------------------------------------------------------------------------

Bejay

 

[Wilderness medic]

Thanks for the info guys! Interesting stuff.

 

[Hamfist]

There aren't even any fish where I want to dredge

 

[winners58]

low flows, dams, mild winters. all flush out the smaller cobble fish need to lay their eggs
mild winters push all the small rock into massive piles along streams, the state does some
gravel augmentation which may or may not work if mother nature cooperates.
dredging targets areas with larger rock, when finished the larger rock is used to fill the holes
the tailings spread downstream, another benefit of dredging is the small disturbance sends
the bad organisms that attack smolts, downstream where they are cannibalized by other bad organisms.
the disturbance, dredge holes, in some cases even the turbidity can give the fish a break.
A ban on motorized mining does not Identify an environmental standard to be achieved but instead restricts a particular use.
there is no scientific basis that any or all forms of motorized mining necessarily causes an adverse affect on wildlife.

 

[jsurddy]

All the silt that floats around in our glacier fed rivers up here in Alaska doesn’t hamper the fish population at all. You cant see more than an inch or two through the water in these rivers. On an average summer we see many floods in the creeks and rivers that fill the water with more dirt and debris than any group of dredges can stir up. There just aren’t enough dredges out there to match what nature puts out many times a year.