What the Monadnock Region flood mayhem says about the future of rain in NH
As the atmosphere warms, rain is heavier and falls with more intensity
Dave Olmstead listened to the deluge of water carrying rocks and logs at high speed during the early morning hours of July 10. He didn’t get much sleep that night, after part of the Forest Lake Dam on his property in Winchester collapsed.
The water had been creeping up all day, and despite efforts to limit the damage with sandbags, erosion around the side of the dam’s spillway created “a huge gap,” he said.
The Forest Lake Improvement Association sent out an email blast with the subject line, “THE DAM GAVE OUT.” As of Monday afternoon, Olmstead estimated he’d lost 15 feet of lawn and that Forest Lake had been reduced by 4 feet, as water escaped into the Ashuelot River.
“I was really blown away,” Olmstead said. “I didn’t think the water would be that strong to tear apart a concrete spillway.”
Just hours earlier, about two miles away where Kapper Drive intersects with state highway Route 10 in Winchester, Denise Erway and her family couldn’t believe what they saw when they ventured out in the rain – water “eating away at the road.”
A member of the fire department on scene recommended they evacuate, so they did – to a hotel in Keene for the night. When they returned to check on their home the next day, they found what looked like an apocalyptic scene. The pavement of the state highway appeared as though it had been crushed, pulverized. Part of the road had completely collapsed.
The southwestern corner of the state was pummeled by quick and heavy rain that came at the tail end of the weekend, leading to washed out, impassable roads and evacuations. The towns of Winchester and Swanzey both opened emergency shelters for residents who left their homes or couldn’t access them.
Jon Palmer, a meteorologist for the National Weather Service in Gray, Maine, said a trained spotter in Swanzey registered 4.45 inches of rain on Sunday. Updated preliminary estimates on Tuesday pegged Swanzey with 4.52 inches.
The mayhem in the Monadnock Region – along with scary flooding scenes in Vermont and New York – followed what in many ways felt like the rainiest month in recent memory in the Granite State. Final tallies show it wasn’t, but it did align with the current estimates of increasing extreme precipitation events in the Northeast.
How rainfall in NH is changing
In Manchester, it rained 23 out of 30 days in June, and in Rochester, 21 out of 30, said Palmer. But in terms of rainfall totals, the month didn’t break any major records. Rather, it was the frequency of rain that made it seem that way.
Mary Stampone, the state climatologist and associate professor of geography at the University of New Hampshire, said the statewide rainfall average for June – 6.3 inches – was “definitely above normal, but we’ve seen worse.”
The record for June was back in 1922 at 10.46 inches, Stampone said, and more recently, both June 2015 and June 2013 saw more than 7 inches.
It’s the persistence of this summer’s rainfall that’s getting people to take notice.
On Monday, Palmer said, the National Weather Service had a flood watch in place “for nearly the entire state of New Hampshire, except for the Seacoast and Manchester area.” The ground was already saturated and surface water levels were high, with more rain on the way.
“We are in a very, very wet and active pattern,” Palmer said. “It does not look like we’re going to see a change any time soon and in fact, we are keeping our eyes out for another potential flooding event on Friday (July 14).”
Extremes are becoming more extreme, experts say – the dry is drier and the wet is wetter.
An April 2022 Climate Central analysis found that climate change is “supercharging the water cycle,” leading to heavier rainfall extremes in many parts of the U.S. Ninety percent of the 150 U.S. locations analyzed now experience more average rainfall per hour than in 1970, according to the report.
A recent study out of Dartmouth echoed those findings for New Hampshire and the Northeast. Specifically, events that bring 1.5 inches or more of heavy rainfall or melted snowfall in one day are anticipated to increase 52 percent by the end of the century, the study said.
Peter Girard, vice president of communications for Climate Central, a nonprofit organization that communicates climate change science, effects, and solutions, said historical data analysis for the city of Concord, for example, shows approximately 22 percent more rainfall over the last 40 or 50 years during the hours when rain happens, meaning rain is heavier and falling with more intensity.
As the atmosphere warms, Girard explained, it can hold more water: approximately 4 percent more moisture for each degree of warming.
Flooding in Cheshire County
State emergency management officials issued strong messaging on Sunday as Cheshire County communities were pounded by rain and subsequent flooding. Robert Buxton, the state’s director of Homeland Security and Emergency Management, told residents and visitors alike to “never” drive through flooded roadways. Most flood deaths happen in vehicles, he said.
On Tuesday, Gov. Chris Sununu was in Winchester touring the damage around Forest Lake.
In battered Swanzey, Fire Chief William Gould said several roads in the Swanzey Lake area were “really devastated.” In an interview Tuesday, he said things had begun to calm down, but there was a long road ahead – one that he expects will require federal funding and intervention.
“It’s gonna take weeks, I imagine, to get those roads at least passable,” Gould said. “It will take longer than that to get those roads fully recovered. DPW is working around the clock with that stuff, and they’re bringing in outside contractors. Some of the roads are completely gone.”
Gould said one road collapsed under an ambulance that was actively transporting a patient.
“Thank God we had no loss of life or injuries,” he said. “When it was really ramping up, that was our thought. We really thought we were going to have people in trouble, possibly trapped in their houses.”
Swanzey emergency management and DPW officials have been in contact with people who are “basically cut off,” Gould said. One Swanzey resident who lost power and had a flooded basement posted on Facebook, “My road is gone.”
This story was originally produced by the New Hampshire Bulletin, an independent local newsroom that allows NH Business Review and other outlets to republish its reporting.