How do meanders and ox-bow lakes form?

In the lower course of the river, meanders (bends in the river) form when water is moving faster on one side of the channel than the other. The greater energy of the faster moving water causes lateral (horizontal) erosion, as processes such as corrasion and hydraulic action erode the bank. On the other side of the channel, where there is slower-moving water, deposition is occurring. Over time, this causes a bend in the river, which is called a meander.

Over a long period of time, continual erosion on the outside of the bend (where there is faster-moving water) causes the neck of the meander to narrow. When the river floods, the water takes the shortest route, cutting through the neck of the meander. The fastest moving water is now in the middle of the channel, causing vertical erosion of the middle of the channel, and deposition along both sides. Eventually, the curve of the meander is cut off by this deposition, and an ox-bow lake is formed, independent of the river.