Stream
Meanders are looping changes of direction of a stream.  These may be somewhat sine-wave in form.  Typically, over time, the meanders don't disappear but gradually migrate downstream.  However, if some resistant material slows or stops the downstream movement of a meander, a stream may erode through the neck between two legs of a meander to become temporarily straighter, leaving behind an arc-shaped body of water termed an oxbow lake or bayou.  A flood may also result in a meander being cut through in this way.