Mine Falls is one of Nashua's most treasured landmarks and is loved by wildlife and people alike, including Sustainability Manager Deb Chisholm, who loves spotting beavers while kayaking on the Nashua River.
“If you go out at dusk, you have a better chance of actually seeing a beaver in the water, and when it sees you, it hits the water hard with its tail. It’s kind of cool when you’re out there and you hear that,” Chisholm said.
“For the most part, people are fine with beavers,” she added. “Usually beavers only become a problem for the city when there is flooding.”
Until recently, the city's solution to this problem was to relocate the beavers and poke holes in the levees to reduce the risk of flooding.
“You can move beavers to another location, but because that habitat is beneficial to them, beavers will come back,” Chisholm said. “The Conservation Commission had decided to try out some of these tools to see if they offered an alternative to simply relocating the beavers.”
For the past two years, the Conservation Commission had been considering pond levelers – sometimes called “beaver impostors” – as an alternative method. After considering the best location for testing, a pond balancing system was installed at Mine Falls Park near the Spine Road entrance.
Pond balancers are pipes that run under beaver dams and create a permanent leak to keep ponds at a controlled, safe level.
The inlet of the pipe is equipped with a barrier fence that prevents – or “tricks” – beavers from feeling or hearing the flow of water. The beavers cannot detect the current and leave them alone. The height of the pipe outlet determines the level of the pond.
The city's first experience with pond levelers was in September 2023, when one was installed and subsequently removed in Hassells Brook just two days before a major rain event.
“It was extensive flooding and probably some of the most severe flooding the city has seen in quite some time,” Chisholm said, explaining that the city received 6 inches of rain in just one hour. “Some people look at the pond leveler at Hassells Brook and cite it as the reason there was flooding on properties bordering Hassells Brook. I personally don't agree. The flooding was actually due to rainfall, insufficient culverts, etc.”
The Conservation Commission had allocated money for beaver management and an existing contract with Bestway Wildlife to install two pond levelers. After the installation and removal of the building at Hassells Brook, one remained that the Conservation Commission wanted to use.
Consideration was given to installing such a device at the Buckmeadow Conservation Area on Buckmeadow Drive, but the commission was not yet ready to install one there. Chisholm added that the Buckmeadow Conservation Area has a problem with the overgrowth of phragmites – a type of reed grass – and that phragmites tend to die when water levels are high.
After the Mine Falls park advisory mentioned that flooding caused by beavers was clogging the Calvert, which runs under Spine Road, it was decided that this location would be ideal.
“We really don’t have any local data to suggest whether [pond levelers] “Work or not,” Chisholm said. “I know there are several communities in southern New Hampshire that have used them successfully, but we want to be able to use them all here in Nashua before we suddenly have a whole bunch of them. We'll just try it out [and] We thought the Spine Road area would be a good location.”
These articles are shared by partners of the Granite State News Collaborative. For more information, visit collaborativenh.org.