Stream Restoration Practice Stabilizes Channel

www.agrinews-pubs.com
Martha Blum
2010-01-18

DEKALB, Ill. — Almost 32,000 feet of stream banks were protected in Illinois in 2009 with the assistance of the Natural Resources Conservation Service.

“The NRCS started working on stream channels and banks in the late ‘80s in coordination with the State Water Survey and the Extension Service,” said Lori Younker, Area 3 engineer with the NRCS.

“We were doing vegetative work and in the mid-’90s, we transitioned to harder engineering and now we use rock structures for the work.”

Streams like to meander — they do not like to be straight.

“If streams were left to their own devices, they would work their way back and forth across a stream corridor,” explained Younker, who spoke during an educational seminar at the Northern Illinois Farm Show.

“There is probably not a stream in the world that hasn’t been affected by man in some way,” she said. “We’ve cleared timber, plowed the prairie so we can plant crops and drained wetlands to make farm ground, so there is not room for that water to pond in natural depression areas which means it comes to the streams faster.”

In addition, some streams have been straightened and levies have been installed along flood plains.

“We’ve built cities and put in sidewalks and parking areas, which has increased the rate the water runs off,” Younker said.

“So all these things have caused increased runoff and increased the stream slopes, so the water moves faster, therefore the velocities are higher.”

Along with losing ground, there is a cost associated with water quality from stream bank erosion.

“Sediment can account for 30 percent of the costs of water quality,” Younker reported.

According to Younker, the goals of NRCS for completing stream bank restoration include picking the method that best fits the situation, reducing the sediment, protecting the cropland and improving the water quality, while making the project affordable to the landowner.

Younker described four main practices that are used in Illinois for stream bank restoration.

One choice is to use rock riffle to help stabilize the bed of the stream.

“This creates a riffle and pool sequence and streams like to flow in that pattern,” Younker said. “And the fish are able to migrate through the low flow over the rocks.”

If the channel is already stable, a stone toe protection may be installed in the stream.

“This provides protection at the base of the bank and it protects against the high velocity of flow usually in the outside curve of the channel,” Younker explained.

“We like to try to get the channel width back to where it should be because if the channel is too wide, the stream flows too slowly,” she added.

“If you can get the bottom stabilized, then the vegetation will come, so we don’t spend extra money on seeding the banks above the rock — we let Mother Nature do it.”

For streams that are a little larger and stable, a bendway weir can be utilized.

“This is angled rock that goes slightly upstream,” Younker noted. “The idea is the water hits the bendway weir and moves at a right angle to move the channel away from the eroding bank.”

The final practice is a stream barb, which is similar to a bendway weir.

“A stream barb will divert the flow and stick out in the stream, but they’re different because they are taller and angled quite a bit upstream,” Younker said.

Any time work is done to a stream, the landowner must meet the permitting requirements.

“Landowners need to go through the permitting process from the Army Corp of Engineers and the Department of Natural Resources,” Younker said.

Landowners can receive technical assistance from the NRCS and county Soil and Water Conservation Districts.

“The Stream Bank Stabilization Restoration Program is available, which is a cost-share program funded by the Illinois Department of Agriculture,” said Dean Johnson, resource conservationist at the DeKalb County SWCD office.

“When a landowner comes to us concerned about a stream, we have a stream bank specialist go to the site, evaluate the stream and make a recommendation,” Johnson explained.

“We now have three projects on the Kishwaukee River that we’re working on through this program,” he said. “Fall and winter are good times to work on streams because the vegetation is gone and the ground is firm, but if there is a lot of snow, that doesn’t play in our favor.”




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