An ice dam along a river is caused by large changes in temperature in winter. When the temperature gets very cold for several days, ice builds up on the sides of the river. When temperatures rise, rather than melting, the ice breaks off and flows downstream. At some point, it may clog the river as in these photos. Two of the images show an ice dam in a river in Goffstown and New Boston, NH. The last image shows the river as it normally looks. This ice dam is about a mile long. It causes water to back up and may cause flooding in some nearby homes. It will clear when the spring temperatures and rain melt the ice enough that it breaks up.
Milford Street 
Thanks for explaining and illustrating ice dams!
My pleasure. I’d heard of these before but had never seen one. It was pretty interesting to see. Cheers!
wow – great to learn about these and hope this one clears without flooding – and nice pictures
Thank you. NSGS set up monitors to keep an eye on the situation so homeowners can be warned if there is likely to be a problem but my guess is that the homeowners are pretty aware of the current conditions and trends.
yes – my guess is they know and monitor it well –
I remember those when living in Ohio. Hope it all clears nicely without any damage.
Us too. It doesn’t threaten our home but we hate to see otehrs suffer because of this.
Well dam! 🙂
But not “Hot dam!”
Beat me to it 😉
Ha ha ha
Never seen one of these before, thanks for sharing this with us, Chris! Looks mighty impressive!
My pleasure. It was my first as well. Cheers!
Hmmmm. I’m 54 years old and live near a river and have never seen one in my life. It’s the Mississippi River. In New Orleans. I wonder why? 🤔
I can’t imagine why. 😉