International Commission on Irrigation & Drainage Commission Interationale des Irrigation et du Drainage



(7974) Floodway, By-pass floodway, Flood diversion channel, or Flood relief channel
1 - A natural or artificial channel designed to pass flood flow. 2 - Also land, subject to overflow and in most cases adjacent to an existing channel, designed as a floodway. 3 - The channel of the river and those portions of the floodplain in most cases adjoining the channel, that are reasonably required to carry and discharge the flood water of the river. In river engineering the floodways may be classified as : by-pass floodways, parallel floodways and inter-basin (or inter-catchment) floodways. The 1 per cent floodway may be defined as that portion of the 1 per cent floodplain required to convey the 1 per cent discharge safely. The floodway includes all of that channel plus that portion of the floodplain not suited, because of hazard to life and property, for human habitation. Although floodway determination is based on engineering considerations, non-technical factors enter into the establishment of floodway limits, therefore, many floodway configurations are possible for a given reach. Permitted uses in the floodway typically include agriculture, park and open space, restricted parking, and storage.

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