New Research Details Risks of Sea Level Rise and Outlines Needs For N.H. Seacoast

Sep 3, 2019

Coastal flooding after a nor'easter in March of 2018. This stretch of Ashworth Avenue in Hampton Beach was closed after flood waters rose.
Credit Dan Tuohy / NHPR

A new state report says rising seas are on track to cause widespread problems in New Hampshire's coastal communities within decades.

Now, regulators want public input on how the latest scientific findings could guide local resilience planning in the future.

The report is the first big update, required by the legislature, of the state's initial, 2014 analysis of coastal risks from climate change. (Click here to read the new paper: 2019 Coastal Flood Risk Summary Part 1: Science.)

UNH climate scientist Cameron Wake helped write that report and this update, which he says uses the latest science.

He says it supports, as the most likely scenario, that waters off New Hampshire will rise 1 to 3 feet by the end of the century.

Wake says the science also suggests the less likely, but still possible outcomes could be much worse than previously thought.

A storm March 3, 2018 closed part of Route 1A in North Hampton after the sea wall gave way.
Credit Dan Tuohy / NHPR

"200 years from now, our shoreline is going to be very different,” he says. “If we prepare for that, we'll be able to, I think, maintain our quality of life for coastal communities and, really, maintain their existence."

The new analysis is more detailed than the 2014 version, including a range of scenarios for sea level rise impacts over the coming decades.

The report covers, for the first time, how rising waters will affect New Hampshire’s groundwater, drinking water and freshwater flooding. And it includes new research on how changing wave dynamics will affect tides and storm surges.

It also says the melting Antarctic ice sheet will have an accelerated impact on coastlines like New Hampshire’s beginning in 2050. Wake says overall, it underscores that sea levels will continue to rise for generations.

"I think what's important is that communities start to have a discussion about what infrastructure they are going to put the resources into preserve, to buy time for,” Wake says, “and what infrastructure they might decide that they are not going to put the money in to preserve."

The report includes a draft portion with resources and planning frameworks for municipalities.

State officials will hold two public hearings, on Sept. 10 in Rye and Sept. 11 in Newmarket, to get input on that section.

Residents are encouraged to comment at those hearings or online, through Sept. 30, on how the data could inform coastal planning efforts.

The state will update the coastal risk assessment next in 2024.

During a flight January 2019: Homes on Route 1A in Rye abut an icy marsh flooded by high tide, as the coastal highway curves through Ragged Neck, at left.
Credit Annie Ropeik / NHPR / Aerial support provided by Lighthawk