Dam removal aimed at restoring stream flow, improving water quality

Published: Aug. 16, 2022 at 2:56 PM EDT
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COLCHESTER, Vt. (WCAX) - Work is underway at a Colchester farm to remove an earthen dam. And ecologists say that will have a pretty substantial impact on Lake Champlain.

In the middle of the last century, farmers often put earthen dams in streams that flowed through their property. It essentially created manmade ponds used for irrigation.

But what they didn’t know at that time was that those ponds would cause some serious erosion, erosion now being fixed by removing one dam at a time.

Pile of dirt by pile of dirt, crews in Colchester are working to reverse about 80 years of erosion.

“So the dam is an unnatural obstruction of the stream. It was a pretty large dam that blocked the natural flow of the stream,” said Allaire Diamond of the Vermont Land Trust.

In the ‘40s, a dam was built at the Button Farm, halting the flow of Crooked Creek. But the blockage has resulted in sediment from the surrounding bank eroding into the water and getting stuck in the manmade pond.

So the Vermont Land Trust, which is a partial landowner of the farm, has stepped in to restore the wetlands.

“Structurally, when you’ve got trees and shrubs and other woody plants especially, their roots form these massive networks and the network of roots hold soil in place. It prevents erosion, it prevents nutrients like phosphorus from eroding downstream and ending up in the lake,” Diamond explained.

With the help of local engineers and excavation crews, the land trust has now rebuilt the streambed and is working to replant native plants and trees. The roots of those plants will help slow water flowing into the stream before it flows into Malletts Bay.

“We’re really close to the lake here, so everything we do is really going to have a positive impact on the lake in terms of keeping nutrients here,” Diamond said.

There’s more than one way to slow the water flow, according to engineers at Fitzgerald Environmental, who came up with the design plans.

“The restoration approach we’ve taken on this project is what’s called a stage 0 restoration, where we’re not really prescribing where the stream is going to be exactly,” said Rodrigue Spinette, an engineer at Fitzgerald Environmental.

They do that by inputting what are called “roughness elements” into the streambed.

“They’re installing the woody debris, and they’re installing it below the grade of the final surface. And that is to ensure that when the water does come through, it doesn’t erode and downcut into the bottom,” said Jordan Duffy, a water resource engineer at Fitzgerald Environmental.

The roughness elements will not only slow the flow but allow the stream to chart its own course.

“And then aside from that, just physically slowing water, this area is going to be really diverse. So it’s going to have a lot of diversity of plants which is going to be great for wildlife, pollinators,” Diamond said.

A win-win for the farmers who use the land to provide food, and the animals that call the creek home.

The Vermont Land Trust and the environmental engineers on site say there is a big push to remove these dams on farms in our area in order to help water quality and flow. There is local and federal funding available for these projects.

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