| Stream Mitigation and Restoration 2012 |
It is rare to find a more beautiful stream than Little Swan Creek in Lewis County.
Its crystal clear, spring-fed waters meander over the cobble riffles and become turquoise blue in the deep pools. An amazing diversity of fish species inhabit its waters.
The valley is bordered on both sides by layers of wooded hills. With the on-set of spring, the wildflowers wake up to the increasing sunlight and pop out of the earth under the leafless trees.
This text by Cynthia Rorhbach first appeared in Validity - The Voice of Nashville's Trace Communities. |
A riffle constructed from trees harvested on site and boulders from the nearby
road construction slow the flood waters and protect stream banks.
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One can hardly imagine how such a placid stream can become a raging torrent of flood waters.
Just ask any of the residents on Little Swan Creek Road for their accounts of flooding in recent years.
They will tell you about the loss of land from unstable and eroding stream banks, the streamside trees that have fallen off the banks to be carried downstream, and excessively large deposits of gravel.
Similar problems are occurring across the state and the nation, as construction and development of the natural landscape are changing the amount and velocity of storm water flows to our streams. |
Heavy equipment moved tons of gravel, re-shaping over 1/2 mile of stream corridor. |
As you may know, there is new road construction on Highway 412, east of Hohenwald in Lewis County.
This road project is not without its own impacts to local streams and wetlands. Over 1100 feet of small tributaries to Big Swan Creek were enclosed in box culverts for the new road.
Once enclosed, a stream loses all its biological functions – it will no longer support life because it has been cut off from sunlight. Microscopic algae, the base of the freshwater food chain, will no longer grow on the rocks of the stream bed enclosed in a culvert.
Aquatic insects, which under normal conditions are food for fish, will disappear without the algae.
And consequently, fish and other forms of life will not inhabit the sections of stream flowing through culverts. |
A raised earth berm helps contain and control flood waters. |
One of the legal requirements for a road project such as the Highway 412 expansion is that the Tennessee Department of Transportation (TDOT) must spend money to make improvements to other streams to compensate or “mitigate” for the negative impacts from the road work.
Often, the mitigation funds are spent outside the watershed where the impacts occur because the funds are turned over to the Tennessee Stream Mitigation Program, which operates statewide.
However, theHWY 412 expansion created an opportunity to address flooding problems on one landowner’s farm near Hohenwald. |
Limbs and branches from trees removed off the site are installed to form a "wood toe"
at the base of banks on outer curves. Rolls of biodegradable matting stabilize banks
while grass seed germinates. |
Swan Conservation Trust turned in a proposal that was accepted by TDOT to oversee the use of the mitigation funds from the Highway 412 expansion and keep the money locally in the Swan Creek watershed.
A stream restoration project managed by Swan Trust took place during the first months of 2012 on Little Swan Creek just a few miles from the road construction.
The project is located where the creek flows through the Clayton family farm on Little Swan Creek Road.
The stream restoration project addresses all of the storm water and erosion problems with bio-engineering practices. |
The wood toe help captures and holds sediment while protecting banks during floods.
It also creates excellent fish habitat in the deep pools. |
Rather than lining stream banks with rip-rap stone, more natural materials were used.
By creating structures from logs and large boulders, water is now deflected away from the eroding banks and the velocity of flood waters has slowed down.
The depth and width of the stream on the Clayton’s farm was modified, and thousands of tons of gravel were moved to create a new stream profile.
If this sounds like a large undertaking, you are right!
The entire project took more than three months to complete. Over 6,200 native trees and bushes were planted to re-create a stable streamside habitat. |
Over 6,200 native trees and bushes were planted to re-create a stable streamside habitat. |
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Swan Conservation Trust recruited volunteers for the tree planting.
Native grasses were also planted, and practices such as live stakes and live brush layering (branches cut from willows and silky dogwood) were used to re-vegetate and stabilize banks. |
Volunteers plant trees. |
Another important benefit of bio-engineering practices is the enhancement of habitat for fish and aquatic life.
Deeper pools and woody structures have improved the fishery.
The length of the project is nearly a half mile of Little Swan Creek.
Feel free to drive by the site and see this impressive work! |
Riffle structures made from logs and boulders create shallow pools,
important habitat for aquatic life. |
