A natural or artificial embankment that runs along both sides and parallel to a river channel and which traps the river into a narrow channel in all but times of the highest floods.

Natural levees are built up during floods as rivers flow out from their channels. Water, including much suspended silt and sand, flow from the fast-moving channel to the relatively low-moving areas of the floodplain. As a result the silt and sand are quickly dropped and build up into long ridges. Artificial flood control embankments are also sometimes referred to as levees.

(See also: Home Screen-River valleys-floodplains)