Massachusetts is, for lack of a better description, constipated. Its 10,000 miles of rivers, streams and brooks are obstructed by nearly 3,000 dams, leaving the state susceptible to flooding, erosion and habitat degradation.

On average, there is one dam for every 3 miles of river, but the state’s antiquated impediments typically cluster in areas. With the exception of Nantucket, there are dams all across the state. The greatest numbers are in Worcester and Middlesex counties, while Berkshire, Bristol, Essex, Hampden and Norfolk counties each have 100 or more.

Southeastern Massachusetts, for example, is dotted with dams. The long-ignored, or unrealized, problem with river dams was highlighted during heavy rains in 2005, when the near-collapse of the Whittenton Dam, which holds back the Mill River, garnered national attention. If the 173-year-old wooden structure had breached, a 4-foot-high wall of water would have overwhelmed downtown Taunton.

Nearly 2,000 Taunton residents were evacuated, and schools and businesses were closed for several days.

The crisis — averted when the Army Corps of Engineers installed a temporary stone spillway to reinforce rotting wooden beams — led to the creation of Mill River Restoration, a broad partnership of environmental organizations and state and federal agencies. The partnership is designed to, among other things, restore the Mill River to a free-flowing river that provides passage for fish into Lake Sabbatia and the Canoe River watershed.

The first step in this restoration project was taken last year, with the removal of the Hopewell Mills dam, at Taunton State Hospital. In July, Whittenton Dam was finally removed, eliminating a longtime public safety threat and continuing the recent efforts to restore the habitat of the Mill River and Taunton River watersheds.

This spring, the first river herring in more than a century were spotted upstream of the former Hopewell Mills dam site, making their way from Narragansett Bay to inland spawning areas.

“These rivers are fish factories,” said John Catena, the Northeast regional supervisor for the NOAA Restoration Center in Gloucester. “Soon we’ll see 300,000 to 400,000 river herring swimming past the site of this dam (Whittenton Dam).”

The Mill River Restoration project is nearly complete, with one dam, the West Brittania, left to be removed.

Removing these dilapidated structures, however, is complicated and expensive. It can take years to remove just one, as many factors come into play. Sediment from the Hopewell Mills dam impoundment, for instance, was heavily contaminated. The roughly 13,000 cubic yards of contaminated dirt and dam material was buried under the Taunton State Hospital lawn and then capped with 3 feet of fill. A project like that takes time and money.

In fact, nearly every dam removal project involves grant writing, finding funding — despite the state putting aside money last year to fund such projects, it can’t afford to pay the entire bill, so private money is needed — working with multiple partners and navigating a cumbersome permitting process.

The North and South Rivers Watershed Association and the Norwell YMCA have been working since the early 2000s to remove the breached Mill Pond dam that has vastly altered the Third Herring Brook and North River watersheds.

After nearly a dozen years of working to make this project a reality, the dam behind the YMCA is expected to be removed this fall.

“My husband said I could have have blown up the dam and been out of jail by now,” Samantha Woods, executive director of the North and South Rivers Watershed Association, said.

Dam inventory
The Whittenton Dam scare brought the risks posed by the state’s 2,892 dams into focus. The incident prompted state officials to take action: first with a statewide effort to better document these structures and then, in 2012, with legislation that provided funding for dam removal and repair — about $1 million annually.

Mill pond dams, relics of Massachusetts’ manufacturing history that today needlessly hold back water and disrupt habitats, are largely privately owned — despite the fact many owners are unaware of these possessions.

In fact, many of the state’s dams are more than a century old, many have fallen into disrepair, and only 10 percent still provide energy, drinking water or flood control. The rest are restricting connections between saltwater and freshwater ecosystems, which are critical to the region’s economical and environmental health.

Fifty percent of the state’s tidal wetlands have been damaged by tidal restrictions, and dams block migratory fish from reaching spawning grounds. Dams also cause flood risks to surrounding communities. Seventy-five percent of the 627 municipally owned dams are either in the high or significant hazard category, according to a 2011 state report.

Despite significant investment in dam removal and river restoration, annual flood damage continues to grow, according to American Rivers. U.S. flood damage now exceeds $6 billion annually — more than double the yearly damages seen during the first half of the 20th century.

Even the best maintained dams are inherently dangerous when located in, or upstream of, a residential or commercial center.

In March 2010, a three-day storm that set precipitation records raised the Charles River to a level that threatened the Moody Street dam in Waltham. City officials opened temporary housing to evacuees, though the dam, bolstered with sandbags and boulders, ultimately held.

“There’s this misconception that dams protect properties downstream from flooding,” said Alex Mansfield of the Jones River Watershed Association. “Removing dams helps prevent upstream and downstream flooding.”

American Rivers takes a big-picture approach to removing many of the 80,000 dams that clog rivers nationwide, according to Brian Graber, associate director of the organization’s River Restoration Program.

“You need to build capacity to remove dams and restore rivers,” he said. “You need to build incentives for taking down a dam.”

To provide decision-makers and potential funders a firsthand look at the state’s dam legacy and the importance of restoring rivers to their natural state, an Oct. 2 tour entitled “The Case for River Restoration: Lessons from Southeastern Massachusetts” took participants to dam sites in Taunton, Kingston, Plymouth and Norwell to learn about the many benefits of river restoration.

The Sheehan Family Foundation, Island Foundation, Mass Environmental Trust, Eaglemere Foundation, Associated Grant Makers and the Environmental Grantmakers Association sponsored the six-hour tour. State and municipal officials, nonprofit staffers, including Graber, Woods and Mansfield, and two ecoRI News journalists had a seat on the bus.

River restoration
Healthy rivers increase property value, boost recreational opportunities, attract visitors, reduce water pollution, and protect people and property from flooding. The tour stressed the multiple benefits of river restoration:

Healthy habitat for native fish, turtles, salamanders, birds and riparian forest species.
More resilient ecosystems.
Cleaner water.
Increased public safety.
Elimination of the risk of catastrophic dam and culvert failures.
Reduced infrastructure maintenance costs.
New public access initiatives, including parks, trails, foot bridges and land conservation.
Better-managed stormwater runoff.
Viable near-shore fishery and improved shellfish harvesting.

The removal of dams in the Mill River and Taunton River watersheds also will help return the region’s herring runs to their pre-Industrial Revolution numbers.

“Metric tons of biomass moved up and down these rivers,” William Hinckley, of the Massachusetts Environmental Trust, said as the bus motored between tour stops. “By taking these dams down we are helping an incredibly important resource rebuild itself. Dams changed the habitat patterns of these rivers and wetlands, diminishing that biomass resource.”

Returning rivers to their natural state also reconnects people to the water, said Mary Griffin, commissioner of the state Department of Fish & Game. “It brings people to the river. Canoe and kayak launches are built. The economic benefits are huge. There’s a 75 percent return on investment for every dollar spent on river restoration.”

On-land obstacles
The lengthy battle to remove dams inevitably pits the pro-development sector against the pro-environment sector. It’s also about preserving the historical significance of the dams, even if many of those already removed or others that should be removed are made of concrete and rebar.

Moreover, it involves working with neighbors who have come to appreciate the mill ponds that now abut their properties.

Kingston residents Craig and Eileen Teuton, for one, had long enjoyed the pond — those who work to remove dams refer to them as impoundments — that the Wapping Road dam created by backing up the Jones River.

When the Jones River Watershed Association and others initially approached the couple with plans to remove the dam and ask permission to use their property has an access point, the Teutons said no.

The 60-feet-wide nutrient-deficit pond/impoundment didn’t have any fish and was full of sediment, but that didn’t alleviate their fear of not having it.

“We were afraid of what we were going to lose,” said Eileen, during the tour’s lunch break at Jones River Landing. “It was a dead pond, but it was still a pond.”

The Teutons eventually embraced the reasoning behind the dam’s proposed removal. In late summer 2011, heavy machinery began crossing the Teutons’ yard, ruining their lawn and upsetting their peace and quiet. These minor inconveniences — the construction company repaired their lawn — were well worth it.

The dam was removed several weeks later, and the impoundment eventually disappeared. The health of the Jones River and Silver Lake have improved, and the couple enjoys the new view.

“It was transformed from a dead pond to a lively river,” Eileen said.

Deer now regularly cross the river — they couldn’t swim across the impoundment — and the Teutons’ property stays a lot drier.

“We’re getting ecosystems back to where they were and need to be,” said Dan Sarles of the Wellesley-based Eaglemere Foundation. “We’re repairing the mistakes of the past.”