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Ice jams on rivers raising worries

New Hampshire Union Leader

January 22. 2018 8:13PM
An ice jam forming on the Piscataquog River for several weeks now stretches more than half a mile along the riverfront near the Hillsborough County Fairgrounds in New Boston. (DOUG ALDEN/Union Leader)

NEW BOSTON — Fire Chief Dan MacDonald has reclassified an ice jam on the Piscataquog River with a term he feels is much more fitting.

“It has grown from being an ice jam. I’m calling it a glacier,” MacDonald said Monday.

Stretching more than half a mile, the jam along the Piscataquog has been building for weeks and brought with it a threat of flooding.

MacDonald is hoping the massive buildup holds this week, when surging temperatures and heavy rain have led the National Weather Service to place counties throughout southern New Hampshire under a flood watch through Wednesday.

“That mess has got to melt on its own before any other ice is going to get by it. It’s too big,” MacDonald said.

MacDonald, who is also the town’s emergency management director, said he’s more used to dealing with ice jams and flood concerns in the spring, not late January, and on a smaller scale.

The jam stretches some 3,120 feet, according to the state, covering the Piscataquog along a stretch next to the Hillsborourgh County Fairgrounds east of the center of town.

“It’s pretty crazy,” MacDonald said. “It’s more of a solid mass than a typical ice jam.”

Shane Csiki, administrator of the flood hazards program for the state Department of Environmental Safety, said it is unusual for ice jams to form this early, but not unheard of. Csiki blamed the extreme changes in the weather over the last few weeks after a deep freeze that formed a think layer of ice on the surface.

“When we had the warm temperature spike and the rain recently, that caused river levels to rise and caused the ice to start breaking up,” Csiki said. “The cold temperatures after that caused lot of those broken-up pieces of ice to freeze in place in various locations around the state.”

Csiki said a jam on the Warner River and another on the Saco River in Maine, just across the state line from Conway, are also concerns, although those jams were much smaller than what has formed in New Boston.

In addition to temperatures climbing to the high 40s, the forecast also calls for an inch or more of rain in some areas today into Wednesday. Csiki said the effects on New Hampshire rivers and streams will depend on many variables, including how much falls and how deep existing ice jams run.

“What’s important to remember is ice jams can change without notice, particularly when they start moving,” Csiki said. “When we start having multiple days with temperatures in the 40s or higher, you’re really going to start having an increased risk of melt and potential movement of that ice.”

MacDonald said he will be keeping an eye on the Piscataquog today, but he was more concerned what lies further ahead for the winter and early spring if his “glacier” continues to grow.

“If it’s kind of cold, then it’s just going to get bigger because more snow is going to get on it and it’s going to freeze up,” MacDonald said. “At some point could actually stop the flow before that spring thaw.”

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