A river barrier is a structure built to control the flow of a river. The most common types of river barriers are dams, weirs, barrages, levees, and dikes. A DAM is a barrier constructed across a river to hold back water and create a reservoir. A WEIR is a low barrier built across a river to raise the level of water upstream or regulate its flow. A BARRAGE is a large-scale DAM-like structure built across a river to generate electricity or control flooding. A LEVEE is an embankment built along the banks of a river to prevent flooding. Finally, a DIKE is a long, narrow embankment built to protect land from flooding.