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Section of river along which boundary conditions are sufficiently uniform that the river maintains a near consistent internal set of process-form interactions. (A river segment can contain one to several reaches). As a general rule, the length of a reach should not be smaller than 20 times the mean channel width, although shorter reaches can be defined where local circumstances are particularly complex.

Delineation criteria

  • Channel morphology (particularly planform)
  • Floodplain features
  • Artificial discontinuities that affect longitudinal continuity (e.g. dams, major weirs / check dams that disrupt water and sediment transfer)
  • River confinement

Methods and data sources

Segments are subdivided into reaches by visual interpretation of consistent river and floodplain (bio) geomorphic pattern using

  • Google Earth
  • Orthophotos
  • Multi-spectral remotely-sensed data
  • Lidar data

(Field reconnaissance can provide useful confirmation / additional data)