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NH's infrastructure is aging. How will it hold up with predictions of more flooding and extreme weather?

Olivia Richardson

It’s been a wet summer in New Hampshire. This week, heavy rain caused intense flooding in western New Hampshire and most of Vermont, leaving washed out roads, flooded homes and other damage behind.

As waters recede on Wednesday, flood recovery efforts are underway.

To understand the impact of the last few days on the state’s aging infrastructure and how we can prepare for a future with more extreme weather, NHPR’s All Things Considered host Julia Furukawa spoke with Tom Ballestero. He’s a hydrologist and water resources engineer with the University of New Hampshire’s Stormwater Center.


Climate scientists predict this kind of extreme weather will become the new normal for New England. Can you explain how climate change is tied to the rain, flooding and the heat that we're experiencing this summer?

The predictions for this portion of the globe into the future is for slightly wetter periods, as well as the variability of the weather becoming more extreme. The drier periods get drier, as evidenced by the drought last summer, and the wetter periods get wetter, as evidenced by this summer. So the ground conditions are ripe for runoff and any storms that come our way are going to generate a lot of runoff.

When we get these huge amounts of rainfall that leads to flooding. What is the impact on the state's infrastructure?

The most notable are the culverts and the bridges over which our roads and a lot of our utilities and other infrastructure are housed. So once these floods come and overwhelm the conveyance infrastructure, we start to affect all the other infrastructure, which could lead to anything from landslides, for example, navigation disruption, transportation disruption, crop loss, livestock loss. And the more insidious ones are where you have wastes or contaminants or hazards, such as a propane tank, which can float. And when they float downstream, they may be buried in the sediments and become hidden hazards for the future.

Is replacing old infrastructure a factor in preventing road washouts? I mean, this week we saw entire communities were cut off because of flooding damage. And some of these roads were the only ways in and out of these rural areas.

Absolutely. When I refer to improving infrastructure, for example, culverts or bridges, many of them were sized using rainfall data from the 1930 to the 1950s. And the design data, the design precipitation, we used really wasn't changed until the last 10 to 15 years in many, many states. And so a lot of this older infrastructure is undersized, and therefore, when even smaller floods come nowadays, they're going to overwhelm that infrastructure. The water should be passing under the road and the culverts and the bridges. When water starts to pass over the road, they easily wash out. I know this is a tragic time. These are emergency bases. But now is the time to replace failed infrastructure with the appropriately sized infrastructure.

What does developing climate resilient infrastructure look like in practice?  

The fact that we are seeing much more variability means that the natural systems, the streams, are going to be reacting to all of this. That's the other shoe that's going to drop. There are ways to design infrastructure better in harmony with nature. Whenever we build something, we shouldn't change the fundamental hydrology of the site — don't change the runoff amount. In essence, this is where resiliency is leading us, to try to respect what nature is trying to tell us [about] how things should work.

We're going to have to accommodate climate change into how we design and build things. What that means is, what we really should be doing is, looking at what the hydrology will be at the end of life of our infrastructure. That is the precipitation we need to design around. Such that when we do have to replace this infrastructure, it has given us the service we expected from it.

Michelle Liu is the All Things Considered producer at NHPR. She joined the station in 2022 after graduating from Northwestern University with a degree in journalism.
Julia Furukawa is the host of All Things Considered at NHPR. She joined the NHPR team in 2021 as a fellow producing ATC after working as a reporter and editor for The Paris News in Texas and a freelancer for KNKX Public Radio in Seattle.

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