The Jefferson River ice jam north of Twin Bridges grew considerably between Thursday and Saturday. The cold weather helped create an ice jam that stretches from near the confluence of the Beaverhead and Big Hole Rivers, downstream to Jefferson Acres. The jam is nearly 10 miles long and almost ¼ mile wide in some areas.
There has been some localized flooding of low lying fields and farmland. Hells Canyon Road near the Iron Rod Bridge has been closed. Madison County Department of Emergency Services will keep an eye on the river over the next week to see what the warming temperatures do to affect water and ice flow and flood potential. The river flow downstream of the ice jam fluctuates regularly, but Madison County DES has noticed an overall decrease in river volume since the third, and largest, ice jam formed near the Sandru Ranch and Sandru Island.
Jefferson Acres seems to be dry and perhaps out of danger for the time being. Further river thawing and unexpected ice jam dynamics could create a different scenario without much warning. Even though Madison County DES does not expect another flood to materialize, the possibility should be kept under consideration.