Norwalk River flows in Wilton since removal of Dana Dam

WILTON — Since the Dana Dam was torn down last September, allowing the Norwalk River to run freely, experts have begun noticing favorable environmental transformations at the site, with even more positive changes anticipated in the coming months.

Removing the dam was a “massive win” and the “biggest project we could do to improve the health of the Norwalk River,” said Gerald Berrafati, Mianus Chapter coordinator for the nonprofit Trout Unlimited, a national conservation organization that protects and restores cold-water fisheries.

“There are over 4,000 dams in Connecticut, the majority of which no longer serve any sort of function or purpose, nor ever did, like the Dana Dam, which was built to create a swimming and skating pond,” Berrafati said. “Dams block migratory fish from reaching upstream spawning habitat, create impoundments that heat up the water, and disrupt the natural transportation of sediments.”

With the dam gone, the water temperature in the Norwalk River in the summer will drop dramatically, which will be good for cold-water fish such as trout, he said. Additionally, migratory species such as eels, herring and sea lamprey from Long Island Sound will gain renewed access vital upstream spawning areas that to the $2.7 million Dana Dam removal project.

The main purpose of the project was to create “aquatic connectivity” on the Norwalk River, said Alex Krofta, ecological restoration project manager for Save the Sound, a New Haven-based nonprofit aiming to improve water quality in the Sound.

The dam had acted as a barrier to the migration of organisms and to natural river physical processes; it prevented the movement of sediment and organic material that create a variety of habitats for organisms that live in the river.

Further, the Dana Dam had a negative impact on the health of surrounding vegetation and altered how the Norwalk River impacted its floodplain in the area north of Merwin Meadows Park and the Trackside Teen Center.

When a work crew tore down the concrete dam in September, it allowed the river to run freely and restored the floodplain in the area along the Norwalk River Valley Trail as well, Krofta said. When the river spills over its banks with intermittent flooding, it deposits debris and sediment on the floodplain and creates fertile and strong unique habitats, which become home to different types of trees, plants and animals, he said.

This particular area of the Norwalk River can now experience a wide range of environmental growth that was impossible with the dam in place, Krofta said.

Diadromous fish, which can migrate between freshwater and saltwater, will be able to move upstream through the former dam site and beyond as early as this spring, he said.

“This project just about doubled the available freshwater habitat in the Norwalk watershed that fish are in from the Long Island Sound,” Krofta said.

Despite the small size of these fish, their historical migration in vast numbers made them a keystone species in both the freshwater and saltwater ecosystems, he said. By removing the dam, these migratory species will be able to travel upstream again – reconnecting the two ecosystems and serving an instrumental role in the food web and movement of nutrients.

Save the Sound intends to use environmental DNA to track the species moving through the area, Krofta said. Organisms constantly shed cells into the water, and a fish biologist from Save the Sound will sample the water to detect what creatures have been there, he said.

“The spring fish migration season is just around the corner, and I’m confident that we will find American eel, river herring and sea lamprey swimming their way past where the dam used to be in the coming months,” added Berrafati.

New vegetation is growing on the restored sections of the site, Krofta said, and should attract wildlife. Water has also been able to spill out over the banks and onto the floodplains several times since the dam was removed, he said.

Crews will monitor the site every year to see what type of vegetation is rebounding and determine whether it’s native or invasive, according to Krofta. Save the Sound and Trout Unlimited are working together to plan a tree-planting initiative for this spring to further restore the site.

“There’s still a lot more work to be done. There are dozens of dams that are still standing in the Norwalk River watershed,” Berrafati said. “We’re actively working toward the full removal of the Cannondale Dam, which was partially breached by Trout Unlimited in 2018, and exploring options for the removal of two dams at the old Gilbert & Bennett factory in Redding — the largest upstream barrier on the river.”

Signs have been put up at the former site of the Dana Dam in Wilton to explain the story of the fish and the impact of the dam’s removal on the landscape and the Norwalk River.

“I’m really excited for folks to take a look at the landscape around them; and understand the history around it and how we’ve impacted it and think about how we can impact it for the better going forward,” Krofta said. “Just because this is the way it is now, doesn’t mean that’s the way it’s always been or the way it always has to be. We can take positive steps for ecological change and ecological restoration on our landscape.”