Clearing the drains: Aiming to improve flow

Written by David Green. Posted in Feature Stories

By DAVID GREEN 

When the banks of ditches and small streams become overgrown with trees and shrubs, and small islands appear in the meandering channel, the usual response is to bring out the heavy equipment and clear the banks down to the soil and do some dredging.

That’s the typical course of action in many Michigan counties, but it isn’t the case everywhere.

In some locales, stream restoration projects are initiated—methods that handle flow problems without dredging and denuding the banks. It’s a matter of understanding how rivers function and allowing the water to handle the corrective action—along with some assistance from engineers.

crekk-clean-vertical A typical drain cleaning project calls for the removal of all plant growth on the stream bank, explained David Mitchell, an engineer with the Lenawee County Drain Commission. Minor dredging might be tackled to remove a sandbar, but since drain maintenance is limited to an expenditure of $2,500 a mile, dredging and bank reshaping is not part of routine maintenance.

Expenditures are held in check because costs are shared by everyone in the drain watershed—whether or not they had an interest drain cleaning.

As an example, Mitchell said, the cost of work underway on Silver Creek at Ridgeville Road, will be shared by property owners from Morenci up to Brown Road where that drain district begins. In total, 845 parcels are included.

A property owner often makes a request for drain cleaning, but in this case the drain superintendent identified the need while driving through the area.

The cost of the Silver Creek project is not yet tabulated, but notices should be sent soon announced the size of the special assessment for each property owner involved.

“It’s a large district and the cost per parcel will not be very large,” Mitchell said.

Property owners within the city of Morenci who are assessed should expect a charge of about $5. The assessments will be added to winter tax bills.

A review is scheduled from 9 a.m. to 5 p.m. April 13 to give property owners the opportunity to examine their assessment.

“If somebody feels their apportionment is not fair, they have 10 days to appeal in court,” Mitchell said.

If the cost of a proposed project exceeds the maximum allowed for maintenance, the person making the request must file a petition for the work by collecting the names of five other people within the district.

The reason for drain cleaning is to improve the work of the drain or creek.

“We want to get the water flowing out of there,” he said.

Trees and brush on the banks collect other debris in the creek and work to slow the flow, Mitchell explained.

Farmers will sometimes request work to help their field tile outlets operate efficiently. Tile outlets buried under silt prevent drainage.

Once the banks are cleared and sprayed with an herbicide, vegetation is allowed to return on its own. Seeding of grass takes place only if banks are reshaped and expanses of soil are exposed.

Alternative

George Palmiter, a pioneer of restoration techniques developed in the 1970s, approaches a project with one goal in mind: Let the river do the work.

Palmiter worked as a railroad switchman, but he was also an avid canoeist who spent a lot of his free time on rivers. He gained nationwide attention for his techniques designed to restore the hydraulic capacity of streams without resorting to channelization and removal of riparian (stream side vegetation).

Trees are left in place—and some are even planted—for three reasons. Trees provide shade that reduce the growth of aquatic plants that tend to retard water flow. Shade also lowers water temperature in the summer, to the benefit of aquatic animals. Trees also anchor the bank, and the leaf litter provides a food source for aquatic life.

Palmiter removes logjams, or in many cases, cuts out the center and allows the buried ends to deflect water to the center of the stream. Eroded banks are often stabilized with logs, bundles of brush and planting of vegetation.

Bank corrections are made by removing selected trees and shrubs where the stream is too narrow. If the stream is too wide, current deflectors are created with natural material. This allows the river to clear out sand bars on its own. This also changes the flow characteristic in problem areas, such as severe bank erosion.

Palmiter’s changes mimic natural processes, allowing silt and sediment to wash out of the stream channel and end up in flood plains or in slow flowing stretches of the stream.

Palmiter was lauded by the U.S. Corps of for emphasizing the importance of shade along waterways. Without shade, Palmiter found, streams fill up with weedy, sun-loving aquatic plants that contribute to slowing water flow. Over time, an open stream will require more human intervention.

Removing all plants also destroys the habitat supporting aquatic life, along with the natural beauty of the steam.

Mitchell said he was not aware of Palmiter’s methodology.

Comparison

In 2000, a comparison between the usual clearing and dredging method and restoration techniques on Mill Creek in Michigan’s St. Clair County.

A study showed an increase in the water flow rate in the restoration areas after Palmiter’s techniques were put into action.

In the dredged areas, sediment began collecting in the creek bed as soon as four months after the work was completed. Algae and weeds were returning to the dredged sites within five months.

Support for aquatic life was rated excellent only at the sites that were never dredged, and the rating remained excellent after intervention using the restoration methods.

The quality of the habitat ranked lower after dredging.

Subsequent studies indicated continuing river health in the portion of the river that wasn’t dredged.

- March 17,2004 

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