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Roads are drying out after NH’s wet week. But with climate change, flooding could be an increasing problem.

Paul DegliAngeli stands next to the confluence of the Saco and Swift rivers. During this week's flood, the water reached above the rocks, he said.
Mara Hoplamazian
Paul DegliAngeli stands next to the confluence of the Saco and Swift rivers. During this week's flood, the water reached above the rocks, he said.

New Hampshire’s roads are starting to dry out after a wet week. But as climate change brings more precipitation and the chance of stronger storms, communities are starting to face increasing flooding risks and new planning needs.

This week in Conway, a few roads in town flooded, making it difficult for residents to move around town. Brownfield Road and River Road both lost pavement and will require repairs.

It wasn’t the worst flooding the town has seen. But town engineer Paul DegliAngeli says these kinds of flooding events are becoming more normal.

“What we're seeing is that those events that used to happen less frequently are now happening more frequently,” he said. “The 100-year storm of the past might now be the 50 or 25-year storm currently.”

The town is starting to use heavier flooding scenarios when planning for new bridges and culverts, DegliAngeli said. And officials have also applied for a grant from the Federal Emergency Management Agency (FEMA) to raise part of West Side Road that gets consistently flooded.

During the latest storm, one resident had a medical emergency and rescuers had to take them across that roadway by boat.

“Climate change is changing the way we think about these things,” DegliAngeli said.

This week's storm washed away some of the asphalt at the edge of River Road in Conway – just some of the damage there.
Mara Hoplamazian / NHPR
Some of the road damage on River Road in Conway after this week's storms.

Jo Sias, a professor in the Department of Civil and Environmental Engineering at the University of New Hampshire, studies how flooding causes roads to fail.

She said there are generally two issues for roads when flooding happens. Underneath the pavement, soil and other natural ground get softer as it gets wetter, taking away structural capacity. Aboveground, flowing water can wash out and undermine pavement as it rushes over.

Part of the current problem, Sias said, is that it’s difficult to track the breadth of the issue in New Hampshire. Emergency short-term road repairs aren’t well documented.

“There’s anecdotal evidence that things are getting worse,” she said. “But, in terms of quantification, we don’t have the data.”

Her team is working on ways to track the implications of flooding events.

Sias says climate science shows water is an increasing threat, but there are steps communities can take to start protecting roads.

“We do have engineering solutions,” she said. “A lot of it is in the planning process, making sure we’re considering what the future conditions are going to be so that we’re not doing something now that could be detrimental in the future.”

Mara Hoplamazian reports on climate change, energy, and the environment for NHPR.
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