PORTSMOUTH – Before it was totally filled in 1907, a saltwater tidal inlet used to flow in and out of what is now the center of the Strawbery Banke Museum property, according to records at the Portsmouth Athenaeum.
“Even though they filled it in, that water still comes in with every tide, although it’s a couple feet below ground,” Rodney D. Rowland, the director of facilities and special projects for the museum, said this week. “As the tide has been rising, as sea level has been rising, we’re seeing that creep up and it’s impacting our basements, so we’ve got groundwater intrusion from sea water pumping up from underneath.”
The flooding and sea level rise from the nearby Piscataqua River, which he believes has worsened in the past decade, are damaging the historic homes on the property.
In addition to the groundwater intrusion, the homes and property are also being threatened by surface water buildup, Rowland said, as he showed visitors around the 10-acre site this week.
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“The surface water is what they’re dealing with at Prescott Park,” he said about the city-owned park located on the banks of the Piscataqua River and across the street from Strawbery Banke. “You look to the south and the South End is higher than us, you look to the north and the North End is higher than us. All that water is draining right here, which historically is what they wanted, because this is a tidal inlet.”
In the past, the stormwater could flow into the inlet – which was called Puddle Dock – and then out to the river, he said.
But now because it’s buried under two feet of ground, “all that stormwater ponds right here,” he said.
“So now we are getting these massive dumps of two, three inches in an hour,” Rowland said during heavy rain events. “This just fills up like a massive bowl.”
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Damage taking toll as flooding is common
Photos provided by museum staff show the field at Strawbery Banke totally covered by water, water rising up to the clapboard levels on a historic home and more than a foot of water in a basement.
Rowland calls the 1795 Shapley-Drisco House the “poster child” for how rising sea level has impacted the historic homes at the living museum.
“During a King Tide, within a two-hour tide cycle, we’ll have 16 inches of water in the basement,” he said.
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King Tides typically occur once a month, sometimes for a few days, he said.
“They’re higher in December, January and February, so this is when we’re really seeing the impacts,” he said.
The 226-year-old Shapley-Drisco House is an exhibit at Strawbery Banke, and its second story is rented out as commercial offices, he said.
That rental revenue “helps us be a museum,” Rowland said.
But the continued water inundation is causing a variety of issues in the historic home, including “mold, mildew, wood rot, brick decay, mortar crumbling and foundation crumbling,” he said.
In addition to the basement flooding, floorboards on the ground level have popped because of water damage, he said.
“That’s from the water eroding away at the supports,” he said during a visit to the home.
Museum officials are not sure the historic home’s chimney can be salvaged because of the damage the salt water has done to it, he said.
“The salts have worked up into the mortar and brick, and you can literally scrape them with your fingernails and see them crumble,” Rowland said. “We’re seeing it raining down from the upper floors, the fireplace will be full of brick that has just fallen.”
While the chimneys decompose faster, the wood “obviously is pretty old, so it’s taking a beating as well and the foundation is collapsing in the front here.”
Filling in the tidal Puddle Dock Pond “is part of the problem,” Rowland said, because “the water used to have free flow, and now you have this weight on it and it squirts it into other areas.”
But at the same time, until the last decade, “this building never had a problem until the water, until sea level rose to a point where it impacted the basement structure.”
That inundation is taking place despite the fact that the Shapley-Drisco House is “450 feet from the river,” he said.
The 1695 Sherburne House is the second oldest home in Portsmouth, Rowland said.
The home is currently being researched so it can be used as an exhibit at the museum, he said.
“And in the process of doing research to understand the buil, we discovered the chimney, which the museum built in 1967 as a reproduction, had literally begun to sink into the mud because of saltwater intrusion. This massive chimney began to move this way because the framing was tied to it,” he said as he stood near the Strawbery Banke lawn. “It was going to take the building with it.”
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Museum staff decided they needed to remove the chimney in order to save the home, he said.
“And sure enough when they took it down, when the last brick was removed, the large structural beam actually groaned as the pressure was released,” Rowland said about the chimney, which was removed a couple of months ago. “It was a big deal, it was a big problem.”
Funding and education seen as path forward
The museum is attempting to address the surface water and groundwater threats by raising $500,000 through its Sea Level Rise initiative, he said.
“It’s our attempt to begin to address some of these issues. The initiative is not only adapting our site to handle the water, and to protect our buildings, but it’s also to teach,” he said. “We’ve decided that this is too big an issue, not only for us, but for the world, and the United States, that we need to begin to educate people about this.”
Part of that education will be to help people understand that there are two possible futures: one where sea level rise is addressed and one where it isn’t.
“There’s a future if you’re proactive and you help the situation,” he said. “It’s supposed to engage our visitors and make them understand they can make a difference if they are careful about how they live their lives.”
People interested in helping Strawbery Banke can email Rowland at rrowland@sbmuseum.org.
The Link LonkFebruary 27, 2021 at 05:02PM
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No holding back the tide: Strawbery Banke's historic homes threatened by sea level rise - Seacoastonline.com
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