Removing Dams: Benefits for People and Nature

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Old Colony Historical Society, Taunton, MA
River herring provided a source of food for early residents of southeast Massachusetts.

“Schools and businesses were closed for a second day and thousands of residents still couldn’t go home Wednesday as a weakened timber dam threatened to give way and spill a 6-foot surge of water into downtown Taunton.”

“Impassable dams have undoubtedly been the immediate cause of the decline of many fisheries, and a direct relation can be shown between the number of impassable dams on a stream and the condition of the fishery…”

There are 2,918 dams on Massachusetts waterways; about two hundred of those dams are located on the streams and smaller rivers that flow into the Taunton River in the southeast corner of the state.3 Dams have contributed to the degradation of natural systems and the decline of fisheries in this area, and they also pose a real risk to public safety. Removing old, unused, and unwanted dams can remedy these problems.

The Taunton River runs through a gently sloping watershed in southeastern Massachusetts, nestled between Cape Cod and the Rhode Island border. The river is over 40 miles long, and it is the largest contributor of freshwater to Narragansett Bay. Smaller tributaries connect important headwater ponds and wetlands to the mainstem river. Hockomock swamp, for example, at 16,950 acres, is one of the largest wetlands in New England. This diverse watershed contains 45 species of fish, 154 species of birds, river otter, mink, and gray fox, and globally rare species such as the Atlantic sturgeon and bald eagle.4,5

The Taunton watershed has been inhabited continuously since at least the Early Archaic period, 9,500 to 7,000 years ago. Archaeologists have found evidence of many early Native American sites near the Taunton River and its tributaries.6 People used the abundant and diverse plant and animal resources available along the river, and remnants of Native American fish weirs used for trapping river herring are still visible today.4 The watershed was also one of the first areas that Europeans colonized—the town of Taunton was incorporated around 1640. The communities that sprouted up in the region used the river for transportation, as well as a source of food. Early settlers caught shad and river herring during the annual fish migrations, and then dried and preserved the fish for the coming year.4 People continue to use the river for recreational fishing, boating, and swimming. In 2009, Congress designated the Taunton River as a National Wild and Scenic River, in recognition of its outstanding natural and cultural resources.


Old Colony Historical Society, Taunton, MA
Workers at the Reed and Barton Factory along the Mill River in 1909. The West Britannia dam once helped provide power to the factory; the dam is now slated for removal in 2015.

Unfortunately, the Taunton River’s valuable natural resources and the present-day human communities are impacted by a relic of the area’s cultural history: dams. European settlers, in addition to using the rivers for transportation and a food source, also used the rivers for power, constructing dams along the waterways to run mills and factories. Colonists built the early dams for small industries, such as sawmills and gristmills. Later, larger industries developed, and dams provided power for textile factories and ironworks.6 Dam construction reached a high point around the Industrial Revolution, and many of the dams remain in place today. One example is the dam on the Rattlesnake Brook in Freetown, MA. This dam, built in the 1870s, provided power for the Crystal Springs bleachery, which dyed and bleached cotton piece goods. For many years, this bleachery was the town’s largest employer.6 The bleachery buildings are long gone, but the dam remains. Around 90 percent of the dams in Massachusetts no longer serve their original purpose,8 and with the mills gone, these dams are now owned by municipalities, individuals, businesses, agencies, and other organizations.

Dams block the natural flow of rivers, causing sediment to build up behind the dam, starving the river downstream of the silt, sand, and gravel needed to maintain the riverbanks and natural riverbed. Heat from the sun warms the water impounded behind the dam, changing the natural temperature conditions and providing an advantage to non-native species. The impounded water also collects pollutants, such as excess nutrients flowing off fertilized lawns, leading to water quality problems.

Dams stop fish from reaching essential spawning and rearing grounds. Migratory fish, such as blueback herring and alewife (collectively known as river herring), need to swim from the ocean, where they live the majority of their life, to upstream reaches of rivers and ponds, where they spawn. A recent federal study found that dams and other barriers are the top threat to river herring populations.9 River herring were recently considered for listing on the Endangered Species list, and the river herring fishery in Massachusetts was closed in 2005 due to low population numbers.

In combination with other impacts, such as commercial fishing and pollution, dams have severely affected the populations of many migratory fish species. In the Taunton Watershed, dams block migratory fish from accessing approximately 50 percent of the available river habitat in tributaries of the Taunton River.10 These species are a crucial part of the oceanic food web, providing food for commercially important fish species that provide a source of income for communities along the coast. In Massachusetts alone, the seafood industry generated $7.8 billion in sales impacts, $2 billion in income, and 98,000 jobs in 2011.11


Massachusetts Division of Ecological Restoration
The Whittenton Mills dam on the Mill River in Taunton, MA was damaged during a storm in 2005.

In addition to harming the natural environment, dams are also a risk to public safety. They are an attractive nuisance, drawing fishermen, swimmers, and boaters into dangerous waters. One study found evidence of at least 48 injuries and 191 drowning deaths at low head dams (the researcher identifies these as dams 3–5 meters in height) in 30 states between 1970 and 2010.12 In Massachusetts, only about 8 percent of dams have flood control as their primary purpose,13 and in fact, dams can actually cause flooding upstream by holding water back during storms. Old and unmaintained dams, like many in the Taunton watershed, are also at risk of catastrophic failure when flood waters build up behind the structure and put additional pressure on the aging construction. Sudden failure or overtopping of the dam can send floods of water and debris into downstream communities. In Massachusetts, nearly 70 percent of the state-regulated dams are classified as High or Significant Hazard, meaning that the dams are in locations where failure has the potential to cause loss of life and/or significant property damage.13 Many of these dams are in unsafe condition (at high risk of failure) or poor condition (having major structural, operational, maintenance, and flood routing deficiencies).14 Dam failures in West Virginia, Idaho, Pennsylvania, and Georgia in the 1970s resulted in 220 deaths, destruction of hundreds of houses, and hundreds of millions of dollars in damage.15

Since 2005, officials in two municipalities in the Taunton River watershed have declared emergencies because of the threat of dam failure. When the Whittenton dam, originally built in the 1830s, threatened to fail during storms in 2005, authorities evacuated 2,000 residents from downstream neighborhoods, closed businesses in downtown Taunton, and repaired the dam under emergency conditions. The full economic impact of this emergency, including the loss to businesses, was estimated to exceed $1.5 million.16 During a storm in 2010, concerns about the failure of another aging dam, the Forge Pond dam on the Assonet River in Freetown, MA, led to evacuation of residents and the decision to breach the structure to release the pressure of the flood waters.

The solution to these environmental and societal issues is to remove the problematic, aging, and unused dams from our rivers. Dam removal is a one-time cost that restores river processes and permanently eliminates the public safety risk caused by the dam. However, in practice, removing dams can be quite challenging. Concerns from the neighboring community, lack of capacity, and high costs regularly deter dam owners from removing dams on their property. Communities often want dams to remain to preserve the history of an area, to maintain the impoundments that people use for fishing and recreation, or because they are concerned about changing the system that they know. Even if dam owners want to remove their dams, managing a dam removal project is beyond the ability of most owners. The project needs a manager or management team to meet with regulators, conduct outreach, oversee engineering and design, file permits, and raise funds. Obtaining permits and designing dam removal projects can be challenging, especially when sediments behind the dam are contaminated with pollution from past industry in the area. Regulations that are not designed for habitat restoration, but still govern dam removal work, can lead to a long, challenging, and costly permitting process. And dam removal projects aren’t cheap—the design, construction, and project management costs of these projects can range from tens of thousands of dollars up to the millions.


Cathy Bozek/TNC
The site of the former Whittenton Mills dam in Taunton, MA one year after the dam was removed in 2013. Fish passage, instream habitat, and floodplains have been restored in this reach of the river, and the risk to the community has been removed.

In the Taunton watershed and throughout Massachusetts, The Nature Conservancy is working in partnership with federal, state, and local agencies and other nonprofit organizations to build support and enable conditions for dam removal projects. This partnership is working with dam owners to remove dams and we are seeing results from both the environment and public safety. The organizations within the partnership are sharing the load of managing engineering contracts, reviewing plans, conducting public outreach, and building support with local communities and leaders. The partners have brought in funding for projects from state and federal grants and private donations. This funding acts as an incentive for dam removal by reducing the cost to the dam owner. The partners are also supporting improved legislation and regulations that promote and facilitate dam removals, and we are completing dam removals that serve as examples of success to inspire future projects.

In the past few years, The Nature Conservancy has partnered with a seemingly unlikely alliance to rally the Massachusetts legislature to support a bill to improve dam safety regulations and provide a funding source for dam removal. This alliance included municipal associations, water suppliers, engineering professionals, and other conservation organizations—all of whom supported dam removal for their own reasons. This diversity of support gave the message credibility with Massachusetts legislators, and after first considering the bill in 2005, they eventually passed the “Act Further Regulating Dam Safety, Repair, and Removal” in late 2012. The bill provides funding for dam removal through a state revolving loan fund to repair or remove unsafe dams. It also enhances the authority and requirements of the Massachusetts Office of Dam Safety to assess dams, ensure dam owners have emergency action plans and address safety issues, establish an inspection process and schedule, and importantly, increase fines for noncompliance from $500 per day up to $5,000 per day. This bill gives dam owners the incentive to remove dams, both to avoid the financial costs of dam maintenance or noncompliance, and to remove the liability of owning the structures. The bill also provides funding to create an additional incentive for removal: grants are available for design costs and loans for implementation make the expenses manageable by spreading the costs over many years.

Other important policy improvements include proposed changes to the state permitting process for aquatic restoration projects, like dam removal, that benefit rivers and other natural systems. These changes would ease and streamline the permitting process, to reduce costs and shorten the timelines for permitting these projects.

Perhaps the most significant headway in building support for dam removals has come from the successful projects themselves. As of 2014, there are seven dam removal projects in the Taunton River watershed that have been completed or are in the works. On the Mill River, a tributary that flows through downtown Taunton, The Nature Conservancy and the other members of the Mill River Restoration Partnership have collaborated to remove two dams and provide fish passage at a third. Project engineers are in the process of designing the removal of a fourth dam on the Mill River. With that final project, river herring will have access to critical spawning habitat that has been unavailable for 200 years. We focused our dam removal efforts in this watershed because of the important upstream habitat blocked by dams and the likelihood that removing barriers will result in a resilient, healthy river system where we will have measureable benefits. These projects provide both a learning tool for project proponents and an outreach and education tool for other dam owners, communities, and legislators. Through these projects, we have learned and shown others how to manage contaminated sediment, work with permitting agencies, preserve knowledge of the history of the dams and the associated mills, remove the dams safely, and restore the sites to a functioning river system.


US Fish and Wildlife Service Northeast Region
The aging West Britannia dam and mill in Taunton, Massachusetts. This is one of several dams being removed in collaboration with the MA Division of Ecological Restoration, the U.S. Fish and Wildlife Service, and other partners.

There are numerous ways to measure the success of these dam removal projects. In terms of public safety, one of the dams removed from the Mill River was the Whittenton dam, the structure that threatened to fail and flood downtown Taunton in 2005. With that dam gone and the river system restored, water from storms can be absorbed and stored in the floodplains along the edges of the river, and there is no longer a hazardous build-up of flood waters behind an unstable structure. Removing dams throughout the watershed improves public safety in downstream communities, providing benefits to residents and public infrastructure.

The return of migratory fish is an indicator of the environmental benefits of dam removal. In 2013, the Massachusetts Division of Marine Fisheries monitored the first runs of migratory fish to pass by the former Hopewell Mills dam site on the Mill River in 200 years. The monitoring results show that river herring, American eel, and other species quickly came back to the new habitat, and scientists are hopeful that future dam removal projects and increases in available habitat will lead to larger fish populations in the coming years. Another tributary of the Taunton, the Nemasket River, hosts one of the largest river herring runs in New England, and conservationists anticipate that, in combination with other work, improved habitat from dam removals may strengthen and build this core population.17

So what are the hopes for the future of dam removal in the Taunton watershed? We expect that, as successful projects and enabling legislation build support for dam removal, more projects will happen in this region. With more available habitat and more natural river conditions, migratory fish populations will likely increase, providing support for the commercial fisheries at sea, and perhaps leading to the opening of the fisheries in state waters. We expect that the communities in the Taunton River watershed will be spared the risk of catastrophic flooding from dam failure and the expenses that are incurred during emergencies when dams threaten to fail. We also expect that if rivers are allowed to flow naturally, they will be more resilient to a changing climate and impacts from development, allowing these systems to remain healthy and provide important benefits into the future.

This article was improved by comments from Beth Lambert, Amy Singler, Alison Bowden, and Bill Napolitano.