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Study: Twice As Many N.H. Homes At Risk From Flooding Than Federal Maps Show

First Street Foundation

A major new study says federal flood maps have far underestimated how many properties in New Hampshire and nationwide are at risk from substantial flooding, now and in the coming decades.

The report, out Monday, comes from a range of academic institutions and the nonprofit First Street Foundation.

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It finds that New Hampshire has nearly 65,000 properties at risk from substantial flooding – not just on the coast, but also in cities and near inland rivers. The study says that number will increase by about five percent in the next 30 years.

Nationwide, the average increase is nearly 11 percent. It's much higher in places like Louisiana and Florida, which are on the front lines of climate change.

The study shows more than twice as many New Hampshire properties at risk from flooding compared to federal flood maps, which are used to manage flood insurance and disaster aid. Those maps have especially underestimated the risk for homeowners in Hillsborough County and other non-coastal areas. 

First Street executive director Matthew Eby says their model incorporates climate change and other environmental factors to assess the risk of flooding down to the level of individual properties, including in places that federal flood maps don't cover.

"We've also taken that and then adapted it into the future so that you understand what the risk will be like in 30 years, so you have a full perspective for a property, and that is available to the individual now,” he says.

Homeowners can explore the data and see the past, present and future flood risk of their property by searching for their address here.

Annie has covered the environment, energy, climate change and the Seacoast region for NHPR since 2017. She leads the newsroom's climate reporting project, By Degrees.

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