Flood bypass

A flood bypass is a region of land or a large man-made structure that is designed to convey excess flood waters from a river or stream in order to reduce the risk of flooding on the natural river or stream near a key point of interest, such as a city.

Flood bypasses, sometimes called floodways, often have man-made diversion works, such as diversion weirs and spillways, at their head or point of origin.

Since the area of a flood bypass is significantly larger than the cross-sectional area of the original river or stream channel from which water is diverted, the velocity of water in a flood bypass will be significantly lower than the velocity of the flood water in the original system.

When not being used to convey water, flood bypasses are sometimes used for agricultural or environmental purposes.

The land is often owned by a public authority and then rented to farmers or ranchers, who in turn plant crops or herd livestock that feed off the flood plain.