Heavy rains follows by a hard freeze has created some ice dams on local rivers, when surface ice becomes broken up by flowing water, creating a jumble of ice chunks that entirely block the surface. This example was the Souhegan River near the Milford Drive on Monday, February 4, 2013. Ice dams usually melt and break up harmlessly, but in the wrong circumstances can lead to localized flash flooding.
Ice dams on area rivers - like our own little glacier
Posted by David Brooks | Tuesday, February 5, 2013
Heavy rains followed by long, hard frost has created ice dams on several local rivers, including the Souhegan (shown above).
What seems to have happened is that the top few inches of the river froze hard, then new flows from the rain during a warm stretch busted up the ice and carried it downstream until it jammed up. The Piscataquog River in New Boston has two dams, one of which extends for a good 100 yards. If we get another heavy rain before they melt, they could cause flooding - but for the moment, they're just cool to see.