Beaver dams are accumulations of logs and wood placed on a stream or river by a beaver to block its’ flow. Beaver dams slow the rate of water and create small lakes or ponds immediately upstream. The dams may be large structures and may contain beaver lodges. Destruction of the dam may result in floods and logjams. They may block river travel routes and may require a portage to circumnavigate. In fantasy worlds, the beavers that create these dams may be anthropomorphized animal-folk. If this is the case, the dam and beaver lodge may resemble human-made structures such as sawmills, logging camps, or watermills.