This has nothing to do with that delicious freezer jam or favorite winter tune. Ice Jams are an annual occurrence where rivers freeze over and break up during spring runoff. Large “bergs” clog bends or narrowings of rivers and can be backed up in a river for miles. With consistent water pressure flowing into these natural ice dams, eventually the power of water causes the river to elevate along with the ice chunks and push itself out of its banks if the ice jam does not break free of its own accord or with human intervention.
At flood stage, an ice jam becomes a very dangerous scrubbing process. The river at this point ends up being reshaped. Any natural or man-made creation in harm’s way will be damaged or even demolished by the sharp scouring ice along with frigid, flooding waters. If you have ever wondered how tree trunks by the river get such bad wounds, so high up, it’s easy to imagine after knowing how ice jams work.
Much is unknown about the exact combination of events which cause ice jams other than they occur after winter's freeze. Studies today are being done on riparian trees. Each ice scouring occurrence is recorded in the cambium layer (live skin area of a tree) annually. It is interesting to note they have a backlog of history and can follow trends, then attempt to match it up with weather. Many tree ring studies in Canada are concentrating on typical ice jam locations to see if they can find a predictable recipe for ice jams to help prevent costly damage and flooding to towns.
Today several engineering attempts are in place to try to control these ice jams; everything from sculpting the river banks to re-enforcing the bends with large rocks drilled into the bankside, and even a really ingenious concrete barricade system spanning across a river like the ram barricades you see at the entrance of store fronts. The concrete pillars are anchored to the bottom of the river bed and protrude above water enough to allow the straining of large ice chunks, which keeps the river from jamming. If the water were to rise quickly, the barricades just get submerged by water. At the same time, water flows freely, fish migrate without hindrance and boaters are not inhibited by the structure.
Whether you did or did not want to know about ice jams today, you have to admit it’s a unique thing to be able to stand in a river, mid summer, fishing away and pausing to actually see and imagine the history the river has around it. Keep your eyes open and stay curious.