Big Changes in the Beaver River

Sometimes Mother Nature is on Our Side

In 2021, RIDEM Fish and Wildlife changed the regulations for the Beaver River, designating the river as catch-and-release only and removing it from the list of trout stocked waters. These changes were implemented to further protect the wild Brook Trout population in the river, addressing added pressures from competition with stocked trout for food and habitat resources, and angler harvest.

Despite these protections, wild Brook Trout in the system still experience natural stressors that influence their growth and survival. Being a cold water-dependent species, they typically inhabit streams that have significant groundwater contribution, which help to maintain cold water temperatures. This is in part the case in the Beaver River, but because the river’s origins begin as a series of ponds, water temperatures become very warm during summer months. Ponds act as thermal sinks, or large areas of surface water that collect solar radiation, which heat water much more than a flowing stream channel. Therefore, groundwater contribution in a stream channel is often not sufficient to mitigate the effects of warm pondwater outflow on a hot summer day. Summer water temperatures often become well above the tolerable threshold of wild Brook Trout, forcing them to move and find suitable habitat. The Beaver River is no exception to this.

This brings us to one location in Richmond, RI, where the Beaver River runs through—the Beaver River Preserve—owned and managed by The Nature Conservancy. Within this approximately 270-acre preserve, a pond existed by means of an earthen dam—until 2023. During a high precipitation storm event in December of 2023, high flows burst through the dam at the Beaver River Preserve, eliminating the storage of water in the ponded area. This allowed the Beaver River to return to its natural channel, leaving mud flats with the exposed rhizomes of aquatic vegetation.

After some review of historical aerial imagery, the story of the pond at the Beaver River Preserve was not as it seemed. From the earliest available imagery of the area (1939 Aerial Photographs, RIDEM Environmental Resource Map), there was no pond at the site despite the presence of the earthen dam. This indicated that the dam had likely been built in the previous century and used as a source of power generation for a mill, like the history of many other Rhode Island dams. But sometime prior to 1938, the dam was breached either by human hands or naturally. In the following years of imagery, no pond can be seen. That is until the early 1980s when the first stages of a pond began to form again. From the 1980s through 2020, imagery indicates the pond continued to grow. Interestingly, the return of the pond coincided with the recolonization of beavers in the 1980s. The section of dam that blew out in 2023 consisted of 40+ years of material from Mother Nature’s engineer, the beaver!

In the broader picture, this natural process completed the work for conservation organizations working to restore cold water habitat, healthy fish populations, and clean water. Freshwater ponds and lakes are abundant throughout Rhode Island, most of which were created in the 19th and 20th centuries for mill power, flood retention, and recreation. Unfortunately, many of these human-created waterbodies negatively affect the ecosystems downstream by way of altering fish communities, introducing excessive nutrients, and promoting conditions that allow invasive species to flourish. Furthermore, dams act as barriers within stream and river networks, restricting upstream movement for fish and other aquatic animals. This can cause significant impacts to populations, limiting the ability of fish to access habitats necessary for spawning, feeding, and relief from high water temperatures and flood events. With that being said, the value of lakes and ponds across the state vary considerably. Natural resource managers and conservation groups are currently focused on identifying human-built dams which negatively impact cold water streams and serve little function in the way of property value, recreation and other ecosystem functions. This was the case with the pond on the Beaver River Preserve. Based on years of monitoring conditions at this site, water temperatures became elevated throughout the summer months, negatively impacting the population of wild Brook Trout and other aquatic organisms downstream.

Now that the dam is gone, a perfect opportunity for monitoring the post-removal condition arises. RIDEM, The Nature Conservancy, and the Wood-Pawcatuck Watershed Association began collecting a wide range of data on the fish community, water temperature, plant community, macro-invertebrates and more. We have also brought in help from URI’s Freshwater Wetlands class to conduct a long-term study on the macro-invertebrate community. This will be important to assess how dam removal affects the community of underwater insects that serves as the primary source of food for fish and other animals in the river.

University of Rhode Island students, during their Wetlands Ecology lab, collect invertebrate samples in the new stream channel within the Beaver River Preserve.

I may have left you wondering where the beavers went. Well, they are still there and have relocated their water storage engineering to the east, impounding a small tributary which flows into the river. This has allowed the Beaver River to remain free flowing. The topic of beavers can be a controversial one, given the problems that they can cause for roadway infrastructure, among other things. Beavers are native to the landscape and fulfill important roles in the ecosystem. As with many other species coexisting on the same landscape with us humans, we must carefully manage them when issues arise, but allow them to carry on with their natural functions on the landscape.

For now, this natural transformation of the Beaver River back to its free flowing, pre-settlement condition is a welcome change. Moreso, it provides us with a case study to better understand changes to a river when a dam is removed. As you can see from the photos, the mud flats don’t last long and new terrestrial life takes over almost immediately, transitioning the drained area to a flourishing grass meadow within the first growing season. We are eager to continue our monitoring and see what happens next. Stay tuned for future updates and take a hike at this beautiful preserve to see the change yourself!