How much will climate change cost New Hampshire’s Seacoast? To start with – $310,000.

That’s the extra amount being paid in Rye to replace a culvert that is 4×5 feet in size with one that is 20×6 feet. The bigger opening is designed to cope with extra water that will be flowing through low-lying parts of the Seacoast in coming decades due to likely increases in storm surges and heavy rains, plus sea-level rise.

“We have 66 culverts in Rye – not a sexy topic, I know . . . and in the past we’ve replaced them in kind,” said Phil Winslow, a member of the Rye planning board and the state Coastal Risks and Hazards Commission, at a press conference Wednesday. “But based upon a study and expectations of the amount of sea-level rise, we’re using that to dictate what the size of culverts should be.”

Hence the larger replacement, which Winslow said would cost $400,000 rather than the $90,000 needed for a 4×5 culvert. He described the extra expense as “some substantive capital pressure on our budget” that will save money in the long run, because replacing washed-out roads is even more costly.

Spurring more such spending to deal with anticipated problems rather than just the current risks is one of the goals urged by a report on coastal climate hazards released Wednesday by the commission after three years of work.

“We’re acting early, responding incrementally, and revisiting and revising as science is updated and becomes more certain,” Winslow said of Rye, repeating a mantra that was given by several speakers at the hourlong press conference in the Legislative Office Building.

The press conference was held so the 36-member commission could release its report about the extent of hazards facing the Seacoast due to the changing climate, and how best to prepare for and handle them.

The commission was created by the Legislature in 2013, although it wasn’t given any funding, a fact noted by the chairman as he apologized for not having more printed copies available of “Preparing New Hampshire for Projected Storm Surge, Sea-Level Rise and Extreme Precipitation.” The full report is available online.

“It was born out of a simple and common-sense concern about the growing body of evidence telling us that the risk of coastal flooding was growing due to climate and other factors, and we need to understand those factors and begin to take action,” said Cliff Sinnott of the Rockingham Planning Commission, the group’s chairman.

The report follows years of research and public hearings that included lawmakers, city officials, representatives of the real estate and insurance industries, planners and scientists. The final report, unanimously adopted by the 37-member group, was touted as an example of careful, bipartisan analysis of a complex situation. It includes many somber warnings, such as:

Science indicates that sea levels along New Hampshire’s 18-mile coast are expected to rise between a foot and 2 feet by 2050 compared to 1992 levels, and by as much as 6 feet by the year 2100. This could cause problems ranging from extra-high “king tides” regularly flooding streets, as is already seen on occasion, to rising water tables undermining roads and tainting wells.

A 6-foot rise would put about 35 percent of assessed property – currently worth $4.4 billion – in the seven towns and cities along the coast at risk of flooding and storm surge.

Precipitation could increase by as much as 20 percent by the end of the century, with “extreme precipitation events” – those which greatly exceed the average maximum rainfall over a short period – becoming far more common, making short-term flooding more common.

It’s recommendations are many. Some are relatively concrete, such as having the state raise any future buildings or structures in flooding-prone areas by 4 feet. Many concern planning and preparation, such as incorporating expected changes in local master plans, having businesses create preparedness plans for flooding and buying properties in high-risk areas before they are built on.

State Rep. Fred Rice, a Hampton Republican, who described himself as the commission’s member least convinced of human-caused climate change, compared the report to war planning he helped do while serving with the Army in Europe.

“We spent all of out time developing, upgrading war plans for any possibility that could happen – if the enemy invaded this way or that way, in this place or that place, daylight or night, winter or summer, what rail lines do we want to secure, what bridges do we want. . . . The likelihood of any event taking place was very, very low, but if that unlikely event did take place, what was the significance? It was very, very, very high,” he said.

This process is similar, he said.

“This is a document for us to be prepared, no matter what the eventuality might be, and no matter what the odds are,” he said. “This is a contingency plan. It’s not a mandate, it’s not a dictatorial set of guidelines.”

Among those involved in the commission was Jonathan Kipp, operations manager for Primex, a firm that pools self-insurance programs for New Hampshire municipalities. He said that climate change-related claims do not appear to be a problem yet along the state’s coastline, but that preparing is smart.

“Let’s plan for it now. If we’re building a high school, let’s use the recommendations so that a claim due to high water doesn’t occur after you have the building built,” Kipp said.

John Rice of the Seacoast Board of Realtors said that coastal hazards do not appear to be affecting sales or prices, but that new construction has the issue of rising water in mind.

“People are coming around to the fact that if you are going to build, you are going to have to build up,” he said. “Towns are mandating that if you want building permits, you are going to have to build up.”

Also present at Wednesday’s event was State Sen. David Watters, a Dover Democrat, who co-sponsored the original legislation to create the group.

He said he hoped the report would prod the Legislature to create enabling laws, which would allow cities and towns around the Great Bay and on the Atlantic Ocean to take action locally.

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