As record rain pounded Montpelier for the second day and rivers raged far beyond their banks early last week, city leaders and first responders were awake deep into the night, huddled around a police station conference table, tensely monitoring a threat: rapidly rising water at the 90-year-old Wrightsville Dam just above town.
Water had risen more than 15 feet since the rain began and was still climbing toward the dam’s top. Already, flooding in the city’s downtown was catastrophic, but if the Winooski River breached the dam, it would bring a whole new level of destruction. Worse, evacuation routes were largely cut off. There was nowhere for residents to flee but to upper levels of the buildings they were already in.
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At about 4 a.m., with gauges showing water just 2 feet short of the dam’s capacity, the officials were told to evacuate the command post. City Manager William Fraser sent an alert, warning of a possible surge that could “drastically add to the existing flood damage.”
It turned out luck was with them. The rain abated in the coming hours, and water crested a foot shy of the dam’s threshold. The feared disaster was averted. But it was a warning: That dam and thousands of others across New England, many of them built a century or more ago, might not be up to the ferocious rains brought on by climate change.
“These weren’t built for the kinds of really big, intense flows that are exacerbated by climate change and human land use activities,” said Christine Hatch, a hydrogeologist with the University of Massachusetts Amherst and a member of the Massachusetts Water Resources Commission. “And so we’re just going to see more of those failing.”
There are some 14,000 dams across New England, many of which are vestiges of a long-past era. Some are relatively new and relatively large, like the Wrightsville Dam, constructed during a spate of Depression-era public infrastructure building. But many more were made in a much earlier period, when the New England economy was powered by moving water and when mill-driven factories were built on rivers everywhere, making everything from textiles to chocolate. In many cases, towns and cities grew up around them, leaving antiquated dams in populated centers where people and property could now be at risk.
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A federal database cataloging 4,010 of the region’s larger dams lists 533 of them, or 13 percent, as being at risk for failure and, if they do fail, causing significant economic loss or death. About 200 of those are in Massachusetts.
Compounding the risk in ways that are not yet fully understood are the intensifying rains brought about by a warming planet. Warmer temperatures mean more water in the air and a roiled atmosphere that brings both periods of drought and the potential for deluge. A recent analysis by the Metropolitan Area Planning Council found that the number of intense, two-day storms in Massachusetts increased by 74 percent from 1901 to 2016, and the heaviest rainstorms now dump 55 percent more precipitation than they did in the mid-1900s. The frequency and strength of the storms are expected to increase as he planet warms.
Dams in Massachusetts are an average of 100 years old, according to the federal database of larger dams, and increasingly will be no match for such powerful new storms.
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“There are a lot of old dams, and that provides, by default, a risk environment,” said Francis Magilligan, a geographer at Dartmouth who studies dams and dam removal. Add an extremely rainy stretch, like the one New England has been experiencing, to the antiquated infrastructure “and the system is primed,” he said.
An example came in 2005, when days of historically heavy rains pushed Taunton’s Whittenton Pond Dam, a half-mile upstream from the city’s downtown, to its limit. Built in 1832, the dam was on the verge of failing, potentially unleashing a 6-foot wave of rushing water. Two thousand people were evacuated from the downtown and dive teams were on hand in case the worst should happen. National Guard troops were summoned.
Pumps were deployed to divert water around the dam, and the structure ultimately held. The near-miss catalyzed the state to pay closer attention to the dams.
Then-governor Mitt Romney ordered inspections of high-hazard dams and vowed to examine what measures the state could take to safeguard them. Since then, the state’s Division of Ecological Restoration has removed over 60 of the state’s roughly 3,000 dams, including three in Taunton, according to Beth Lambert, who directs the division. A removal, which involves slowly draining the basin of water while clearing debris and removing sediment, costs $1.3 million on average.
Six years after the Taunton scare, in January 2011, a state auditor’s report found that 100 municipally owned dams in Massachusetts, all relatively large, were in unsafe or poor condition and that many communities did not have emergency action plans to evacuate neighborhoods.
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In 2019, an analysis by the Associated Press found that 39 high hazard dams in the state were in poor or unsatisfactory condition — among 1,680 nationally in the same condition.
One of the dams highlighted by the AP was the 110-year-old Willett Pond Dam near Norwood, a Boston suburb of nearly 30,000. An inspection report noted that the dam’s spillway could handle just 13 percent of the water flow from a serious flood before it overtopped. If the dam were to fail, hundreds of millions of gallons of water could flood the heart of the city, where more than 1,300 properties lie within the inundation zone, the report said.
Repairing the dam would cost between $1 million and $5 million, according to the 2017 inspection report. Since then, the dam’s owners and the pond’s abutters have been working on plans with engineers to start repairs on the dam in the next few years.
Some oppose the push to repair and fortify dams in favor of getting rid of them entirely. A movement driven largely by conservationists is pressing for the outright removal of many dams, arguing that taking away such obstructions can restore a river’s natural ecology and play a vital role in the health of native fish and other wildlife, which are already threatened by the changing climate.
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“We need to allow species to get to the places that are going to provide refuge from extreme temperatures and floods,” said Keith Nislow, a Massachusetts-based fisheries biologist with the federal Department of Agriculture who researches dam removal and ecological impacts.
Researchers and public officials are now working to determine which of the dams could be removed without jeopardizing public necessities like power from hydroelectric dams or reservoirs that supply drinking water.
Progress toward repairing or removing dams has been slow. Of the 100 dams cited in the 2011 auditor’s report, 40 remain in poor or unsafe condition, state officials said, half of which have received grant funding for removal or repair.
On Friday, citing the recent flooding, the Healey administration said it would give $5.6 million in grants to remove or repair dams, including the Willett Pond Dam in Norwood.
”This week, I saw firsthand the catastrophic flooding impacting many people’s personal and professional lives,” Governor Maura Healey said in a statement. “As we continue to experience the impacts of climate change, it’s critical to invest in programs like this that will enhance our safety and infrastructure.”
Meanwhile, as climate change progresses, experts say the extreme weather the region is experiencing now is just a taste of what’s to come.
A recent study in the journal Climatic Change found that if worldwide fossil fuel use continues to rise through the end of the century, the Northeastern United States can expect an average of 52 percent more extreme precipitation, compared to the period from 1976-2005.
What worries Hatch, of UMass Amherst, is how quickly things can go wrong when extreme rainfall causes an earthen dam to start to erode. “You have this kind of runaway erosion that will cause a very quick failure before you know it and at that point, there’s nothing you can do about it,” she said.
Sabrina Shankman can be reached at sabrina.shankman@globe.com. Follow her @shankman.