The freeze-thaw weather cycle of recent weeks is fueling ice jams in rivers across New Hampshire – including in New Boston, where a huge, persistent blockage could cause flooding this spring.
The jam on the Piscataquog River is more than 3,000 feet long – the length of 10 football fields.
New Boston Fire Chief Dan MacDonald says it's made of foot-thick icebergs that have melted and cracked, then frozen back up into a single solid glacier.
“It's a living thing,” he says, laughing. “It's growing. As the snow mounts onto it and the winter comes back, it's going to grow -- it's going to grow in thickness and it's going to grow in length, and it's going to be much more problematic in the springtime."
The river is flowing freely beneath the ice right now, but MacDonald says colder weather in the coming weeks means the jam probably won't melt until spring.
He says when it does, it could put dozens of homes at risk for slow-moving, low-level flooding -- especially if temperatures warm up quickly.
He says the ice jam will either block the flow of meltwater upriver from it and raise water levels in downtown New Boston, or cause flooding downstream as it melts itself.
"All we can really do is monitor it, and we're prepared to notify people to move, to get out,” he says.
In the meantime, he's considering a little fire department fundraising off the anomaly, which he's named the River Glacier – maybe a lottery to guess its melt date, similar to the annual event on Lake Winnipesaukee. WATCH the New Boston drone footage of the ice build-up on the river, aka River Glacier:
To see Army Corps of Engineers photos and details on ice jams around the country, click here.