Largest log jam

The largest log-jam in history formed on the Chippewa River in Wisconsin, USA, in early May 1880. Low water levels in the river caused the logs being floated to lumber mills downstream to get stuck in the rapids at Chippewa Falls. By 13 May 1880, the jam reportedly extended some seven miles upstream from the falls, and contained around 200,000,000 board-feet (471,947 m^3) of timber. On 13 June, heavy rains allowed the jam to break loose and sweep downstream causing devastating floods in the towns of Chippewa Falls and Eau Claire.

Log jams were a common event in the American midwest and northwest during the late 19th and early 20th centuries. Logging camps would be built in the upper reaches of major rivers to supply lumber mills downstream. Felled trees were stripped of branches and then rolled into the river. This flow of timber was managed by teams of workmen who built dams and booms to steer the logs around obstacles and used long hooked poles to free them when they got stuck.

Even with these precautions, the variable water levels on the rivers meant that the occasional log-jam was an accepted risk of the lumber business. Other notable jams include one of 150,000,000 board-feet on the St Croix River near Taylor's Falls, Minnesota, in 1886 and another of 100,000,000 board-feet on the Mississippi River near Little Falls, Minnesota, in 1908.

A log jam was a tremendous sight, for several miles the river would be transformed into a jagged field of telegraph-pole-sized logs, tangled together at crazy angles. The whole thing would groan and creak from the massive pressure of the water backed up behind it, occasionally erupting in an explosive cacophony of cracks that launched shattered wood and even whole logs high into the air.

When log jams occurred, the lumber companies would dispatch working parties to try to break up the obstruction. They would use tugboats and static steam engines, attached to ropes and cables to wrench sections of the jam free. If this failed, lumbermen sometimes resorted to blasting away sections of the jam with dynamite. Sometimes, as was the case in 1880, the crews were unable to free the logs before the river level rose again, transforming the jam into a fast-moving wall of white water and 3-tonne trees.

This method of transporting timber continued to be used into the mid-20th century, but not on the scale seen in the period from around 1870-1920. This was primarily because the lumber industry simply exhausted the available resources, but stricter regulation and technological changes (log-hauling trucks) also played a role.