Log jam

A log jam is an accumulation of large wood (commonly defined as pieces of wood more than 10 cm in diameter and more than one metre long also commonly called large woody debris) that can span an entire stream or river channel.

Historically in North America, large "log rafts" were common across the continent prior to European settlement. The most famous natural wood raft is the "Great Raft" on Louisiana's Red River, which prior to removal in the 1830s affected between 390–480 km of the main channel. It has been suggested that such extensive log rafts may have been common in Europe in pre-history.