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Keywords:

  • gravel-bed channel;
  • riffle–pool structure;
  • sediment slug;
  • typhoon;
  • bedrock outcrops;
  • sediment supply

Abstract

A six-year monitoring programme characterized the migration/dispersion patterns of sediment slugs generated following typhoon-induced disturbances in 1993 and 1997 along a single-thread gravel-bed stream, Oyabu Creek, on Kyushu Island, Japan. This laterally confined creek comprises riffle–pool sequences with intervening bedrock outcrops. The passage of sediment pulses associated with sediment slug processes reflected, and was controlled by, the riffle–pool structures which provided channel bed roughness, the volume of sediment stored along valley floors, and the distribution of bedrock outcrops. Changes to bed material size following major sediment inputs during the disturbance events also exerted an influence on subsequent sediment slug processes. The sequence of rainfall events, together with changes to channel bed structure, induced different phases in the sediment slug processes. The capacity of a reach to store or trap sediment, as recorded by the longitudinal structure of the channel, varied during these differing phases. Copyright © 2004 John Wiley & Sons, Ltd.