Lamington River dam removed, pushing forward restoration of Raritan watershed – NJ.com

A grist mill dam built in the 1800s has been removed from the Lamington River to reduce erosion and flooding in the region and improve habitat conditions for fish and other aquatic creatures.

The derelict Burnt Mills dam was previously located just east of Tewksbury Township, upstream from the Cowperthwaite-Burnt Mill Road Bridge connecting Bedminster and Branchburg townships.

Its removal was completed in late October by nonprofit organization Raritan Headwaters, which owns an 11-acre nature preserve beside the site.

The project restored the main channel of the Lamington River to its original configuration, which Raritan Headwaters policy director Bill Kibler said had been disrupted by a storm that occurred approximately 60 years ago.

When that happened, the entire stream -- instead of being backed up in the dam and flowing over the dam with the water level -- just went around the dam. So it just created this big artificial, oxbow -- a big horse-shaped bend in the river that wasnt there before, Kibler explained.

The oxbow severely eroded the riverbank near Milnor Road in Bedminster, subsequently increasing flooding in the area and causing neighboring trees to fall into the water.

Courtesy

Lamington River pre-dam removal

To recover the the rivers original streamlined flow, Raritan Headwaters facilitated the dispersal of sediment that had built up over the years and implemented large boulders as a form of safety relief," according to Kibler.

Now almost all the flow goes right down the original bed, down the stream, where the river used to flow a hundred years ago, Kibler said.

While the dams removal is expected to reduce flooding in the Milnor Road-Cowperthwaite Road neighborhood in Bedminster during storms, Raritan Headwaters has also begun to restore the floodplain to further minimize river overflow.

We (created) what they call roughness in the floodplain -- big trees that are in the forest that are anchored down. And when the floodwater hits it, it slows the water down, Dr. Kristi MacDonald, science director for Raritan Headwaters, explained.

Moreover, vernal pools were added to the floodplain to help capture and slow flood waters and provide breeding habitat for amphibians.

Outside of the floodplain, riffles and pools were added to the river to increase oxygen levels, which had previously been depleted by pooled water formed by the dam as the river heated up in the summertime.

The fish and the bugs that the fish eat (both) need a lot of oxygen. And cold water holds more oxygen than warm water -- a lot more oxygen. So if the warm water is warming up, then a lot of the species that live in the stream that provide food for the fish and other organisms will die off, MacDonald said.

MacDonald added that the feeding ability of aquatic wildlife was also jeopardized by sediment trapped by the concrete dam.

Sediment especially impacts the fish food ... maeflies and stoneflies and catusflies, they cant get under the rocks when theres a lot of sediment in the water. They basically lose their home, MacDonald said.

In an effort to further counteract the negative ecological impact of the dam, this spring Raritan Headwaters will plant a variety of trees along the riverbanks.

Theyll be floodplain trees -- sycamores, and probably silver maple, those are species that like to grow along rivers. The forest right now doesnt have a very good diversity of trees, so we want to kind of increase the diversity and make it a healthier forest, MacDonald said.

Invasive plant species will simultaneously be removed from the area.

Some of (the plants), if you leave them there, will grow to an extent that they crowd out all the native plants and they dont function the same; they dont provide the same wildlife habitat ... (vines) will grow and smother the trees eventually, MacDonald said.

Willow stakes will also be planted in the springtime to improve the forest and help stabilize the riverbanks.

You basically just hammer (willows) into the ground like a tent stake. And willows are great for that because they root pretty easily, pretty quickly, and they have a good root system. So once the willows start growing, the root systems helps hold the new banks in place, Kibler explained.

The U.S. Fish and Wildlife Service and the U.S. Department of Agricultures Natural Resources Conservation Service partnered with Raritan Headwaters to complete the dams removal, contributing to the projects cumulative cost of approximately $250,000.

New Jersey State Conservationist Carrie Lindig said that as mill dams get older, landowners in the area tend to grow increasingly impatient to have them removed.

(Removal) takes a lot of money, and it usually takes more than one organization to contribute funding to take them out, Lindig said.

Fish and Wildlife Biologist for U.S. Fish and Wildlife Service Cathy Marion said the project represents a win for both humans and the environment," expressing her desire that similar ecological efforts will be pursued in the area for years to come.

We hope that one day aquatic connectivity is improved in the Raritan Watershed to the extent that migratory species ... will actually be able to return to places like the Lamington River, which they have not been able to access for many years -- probably 100 years," Marion said.

While several dams have been removed along the Raritan River and its tributaries in recent years, the Burnt Mills Dam was the first to be removed by Raritan Headwaters.

According to Kibler, it wont be the last.

There are roughly a dozen or thirteen dams on the South branch of the Raritan River, and theres another eight or ten on the North Branch in our Watershed. Our goal is get as many of those out, and get the river restored, as best as we can, Kibler said.

Caroline Fassett can be reached at cfassett@njadvancemedia.com.

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Lamington River dam removed, pushing forward restoration of Raritan watershed - NJ.com