Officials Monitoring Impacts of Beaver River Dam Breach

By Cynthia Drummond for BRVCA
January 13th 2024

RICHMOND – The storms that brought torrential rain to Rhode Island have taken a toll, not only on roads and bridges, but also, on at least one dam. During a rainstorm before Christmas, strong water flow on the upper Beaver River broke through the 19th Century earthen dam on the Beaver River Preserve.

The Beaver River is a tributary of the Wood-Pawcatuck watershed, which, in 2019, received the federal “Wild and Scenic River” designation from the National Park Service. The Preserve and the dam are owned by The Nature Conservancy.

TNC spokesman Tim Mooney said it was not clear when the dam had failed.

“We don’t know exactly,” he said. “The rainstorm was on the 19th and the Preserve staff went down there on a routine visit. … We discovered it on the 21st.”

Mooney said TNC had been monitoring the dam.

“We’ve had our eye on this dam and what would be the pros and cons of removing it, ecologically,” he said. “It didn’t seem to be at imminent risk of failure, so to be honest, we were surprised to find that it had breached.”

Jim Turek, a restoration ecologist with the National Oceanic and Atmospheric Administration, also serves as Chair of the Richmond Conservation Commission.

Turek said he had tried to learn more about the history of the dam before it failed, but he had not been able to find much information.

“I thought the dam was from the 1880s or so,” he said. “I’m going to try a little bit more research. It was a very old dam associated with a very old mill.

It was an earthen dam and it had a stone spillway which I would best describe as glacial boulders that were used to construct the spillway. That’s like stacking bowling balls, and it looked so funky, I always thought it was going to fall apart, to the point where you get on top there and move stuff around you could knock the thing over.”

Beaver Dams

Mooney said beavers have been active at the dam, adding material to the top of the dam itself and building additional dams downstream.

“Beavers had built on top of it and had also built a complex of dams, maybe 200 feet downstream,” he said. “That beaver dam was at least three feet tall. It was considerable, and some of that is still there. So, where the earthen dam breached cleanly through, the beaver material, the stone, the dirt, whatever, is washed downstream and the Beaver River now flows smoothly through it, and then a couple hundred feet downstream, it encounters this related complex of smaller, beaver-made dams which are intact, but not as tall as they used to be.”

No Rebuilding

“No one is going to come along and say ‘we’ve got a bunch of money for you to fix it,’” Turek said. “It would be foolish.”

Mooney added,

“That dam has been on the radar of conservationists. We have been asked from time to time would we consider removing it. There are benefits to open wetland habitats and there are benefits to free-flowing rivers as well. We had looked into it, but it was just too difficult and too expensive to bring machinery in there to remove it manually, so now, nature has taken care of it for us.”

Turek explained the steps that would be necessary to restore the flow of the river.

“We need to make sure that we clean up that outlet, because right now, that pile of boulders…a lot of it sits in the channel immediately downstream. I want to make sure that during lower flows, that channel reach is going to be passable, especially by brook trout,” he said. “We also want to make sure that the outlet to the pond is dynamically stable. I wouldn’t want to have a slough of material continue to go downstream. The best thing to do is just take some of those boulders and create a manmade riffle to support that being stabilized in a way.  The last thing we ought to do, someone should be monitoring, at least at a minimum, the changes that are going to occur in the plant community, because we know for a fact from many other dam removals, planned dam removals in particular, we always get a native plant community to come back quite rapidly, because there’s a seed bank in these sediments, and they sit there, and we know for a fact, from other dam removals that we have planned and implemented, that some of these seed banks are good and viable for over a century of being submerged.”

More Restoration Work to Come

The Wood-Pawcatuck Watershed Association has also been monitoring the dam. Executive Director Chris Fox, who supports a free-flowing upper Beaver River, described a broader, cold water stream restoration initiative that is currently underway. Participating organizations, in addition to the Wood-Pawcatuck Watershed Association, are The Nature Conservancy and the Rhode Island Department of Environmental Management, which have partnered with the Narragansett Bay Estuary Program. The program administers funding, in this case a $140,000 grant, from the Bipartisan Infrastructure Law, passed by the United States Congress in 2021.

The funds will be used to improve habitats for native fish species such as trout.

“What old, remnant dams, like the one that failed on Nature Conservancy’s property exist, that hold back water and have a negative impact on freshwater fishes’ habitat, creating a pond that gets really hot in the summertime that exceeds the temperature thresholds that species like brook trout can’t tolerate and cause them to have to leave that area of the river because of the water temperature,” Fox said.

And old dams aren’t the only structures impeding water flow and fish passage.

“There is a culvert on Hillsdale Road that is what’s called a perched culvert, which means the exit of the culvert is like a waterfall, so essentially, it blocks aquatic organisms’ passage through the culvert,” Fox said. “So, it’s not just looking at improving habitat for resident wildlife, it also looks at flood resiliency. Using that same culvert as an example, it’s grossly undersized. … That culvert was destroyed in the 2010 flood [and] was immediately rebuilt by the town exactly as it was designed so that they could get the road re-opened (Town officials have indicated that the culvert was replaced in 1999, not in 2010), however, as we’ve seen in these recent storm events in the last few weeks, the road on Hillsdale Road is overtopped several times and not simply because of the dam failure upstream, more because of the volume of water being conveyed in the Beaver River.”

Turek said his mission was to restore the river’s natural habitat.

“My goal in my life is to try to put streams and rivers back into free-flowing natural state to the best as possible and that’s a classic example, trying to restore that stream for native fishes like brook trout,” Turek said. “Because it is a cold water system, the Beaver River, it’s an important system and to try to put an impoundment with a dark bottom that warms up substantially in the warmer season just doesn’t make any sense for supporting cold water fish habitat in the location, or downstream of it. That’s the whole point of it, is trying to bring back an important resource which is a Wild and Scenic River designation.”