1) Path of a cresting river 2) Route of a cresting river 
The channel of a river or stream where the annual rising or lowering of water occurs.
The channel of a river or stream and the parts of the floodplain adjoining the channel that are reasonably required to efficiently carry and discharge the flood water or flood flow of a river or stream.
the channel and adjacent shore areas under water during a flood, esp. as determined for a flood of a given height.