As sea levels rise, history submerged
‘We came to this project 20 years too late,’ says UNH anthropologist
DURHAM, N.H. — Meghan Howey is scrambling to document history before it gets washed away.
She’s an anthropology professor at the University of New Hampshire who studies early Colonial sites along the Seacoast that are in danger of being lost forever to rising sea levels.
What she’s found at those sites challenges the historical narrative about conflict between early colonists and indigenous people in the area, she said. She found evidence of an 80-year period of close collaboration — including arrowheads and indigenous foods — inside of English fortified houses.
“The English here are very different than the Puritans and the Pilgrims. So they’re interacting intensely and closely and in very peaceful ways up to the 1680s with Native people,” Howey said. “That’s a very different story than I think what we tend to inherit.”
But climate change is quickly destroying evidence of that history — as persistent flooding also challenges ongoing efforts to preserve historical buildings, including those maintained by the Strawbery Banke Museum in Portsmouth.
Howey called it a race against time, and said that about 75 percent of the sites her team has tried to find already are gone due to sea level rise. Many of these sites are right along the water, since waterways were so important for transportation, serving as the highways of the 1600s. In less than 100 years, sea level rise could claim up to 14 percent of coastal New Hampshire’s known prehistoric and historic cultural sites, according to Howey’s research.
Compared to 1992, the sea level is expected to rise between 0.6 and 2 feet by 2050, and by 1.6 to 6.6 feet by 2100, according to a New Hampshire Coastal Risk and Hazards Commission report. Sea levels in New Hampshire had been rising by about .7 inches per decade since 1900, based on local tide gauge data. But after 1993, that increased to 1.3 inches per decade.
From 1912 to 2018, sea level has risen between 7.5 to 8 inches in coastal New Hampshire, according to the New Hampshire Coastal Flood Risk summary.
At the Oyster River in Durham, a homestead at the edge of the water is one site Howey and her team found while it was still above water. But the site was so damaged and washed away that it was difficult to retrieve many artifacts from it.
“We came to this project 20 years too late,” she said. “If you think about what we’ve lost, it’s the whole house. It’s all gone.”
Howey and her team use historic records and maps to identify possible locations of old homesteads. Then they create a grid of the area and methodically dig every 5 meters to verify if they can find evidence on the ground matching the records. This homestead was burned in what became known as the 1694 Oyster River Massacre.
“We knew it had been attacked. We knew the family had escaped. So we came looking to the general area,” Howey said. Now, there’s just a slight hump visible where the house once stood and a few bricks and other building materials remain.
What was once a two-room house belonging to the Meader family is now only visible at low tide. Many historic cemeteries that were built near the water have shared that same fate — washing away as water draws nearer. Howey’s most recent research found that in two New Hampshire counties, Rockingham and Strafford, at least 80 historic graveyards are at risk of flooding and washing away.
And those cemeteries shed light on another hidden piece of history — a significant presence of enslaved Africans during the Colonial period.
Howey said she worked for one season at the site before moving on to the next one, with the goal of trying to preserve as much as possible. “I can’t imagine how much is already gone,” she said.
Faced with the same problem, the Strawbery Banke Museum is trying a different strategy to battle persistent flooding and try to protect historic buildings that are still standing and date back over 300 years.
The flooding issues at the 10acre campus are twofold, coming from above in the form of surface water flooding and below from what’s called ground water intrusion.
“Everybody knows about surface water flooding,” said Rodney Rowland, director of facilities and environmental sustainability at Strawbery Banke. “It’s in the news all the time, but nobody’s covering ground water because you can’t see it. You can’t quantify it. And it’s actually happening now, and it’s getting worse.”
Rising sea levels push the water table higher, which can cause flooding and other problems.
The museum worked with the university to install sensors that collect data on humidity levels, water depth, and salinity. Over the last two months, Michael Routhier, an information technology manager at UNH, has installed new wireless sensors in the basement of two museum buildings. The sensor transmits data to a cloud database every 15 minutes.
The sensors are designed to help the museum staff better understand how ground water is moving around the site and how it is connected to tides in the river. Rowland said the data will be used to apply for grants to combat the flooding.
Because the water is so persistent in the basement, it leads to really high humidity levels that can cause mold, mildew, and corrosion.
“This basement is seeing inches of water constantly, at least a couple times a month,” Rowland said. “That means the soils that make up the basement are constantly saturated.”
Without a way to dry out, the humidity levels in those buildings get extremely high, which can damage the structure and the collections housed there, according to Rowland. It’s so wet that green mildew grows on the bricks. “It’s obviously a sick building,” he said.
In the future, Routhier hopes to install more sensors throughout the city of Portsmouth to understand how water is moving.
“We’re looking for potential funding right now,” he said. “The city could use that information to better update their storm water network, to even understand where to deploy resources.”
Ground water alerts could tip off homeowners and business owners to potential damage — furnaces aren’t built to handle high humidity and it can drastically decrease their lifespan, according to Rowland.
The museum is taking other dramatic measures. In July, officials are planning to have one of the historic houses lifted, its original loose stone foundation that dates to the 1860s demolished, and a new concrete foundation poured.
And they’re looking at ways to work with nature and not against it, building rain gardens that can filter and slow down storm water and creating a storm water pond to collect water on the museum’s central lawn called Puddle Dock. That area was a tidal inlet until the city filled it in during the early 20th century — now it will again be home to the water.