Slope-channel decoupling in Wolumla catchment, New South Wales, Australia

the changing nature of sediment sources following European settlement

Kirstie Fryirs*, Gary J. Brierley

*Corresponding author for this work

Research output: Contribution to journalArticle

81 Citations (Scopus)


Within a few decades of European settlement, channel incision transformed discontinuous fiver courses throughout Wolumla catchment, on the south coast of New South Wales, Australia. The development of continuous channels greatly increased sediment delivery from the catchment. This paper documents the character, timing and proportion of sediment sourced from upland valley fills, channel expansion sites, and gully networks. Volumes of material transferred from these sources are compared with estimates of sediment eroded from hillslopes, and the movement of sediment off the slopes to the valley floor is assessed. Although disturbance of slopes resulted in significant movement of materials, most of this material has been stored on-slope, in trapped tributary fills and along lower order drainage lines. The slopes are effectively decoupled from the channel. Sediment accumulation in farm dams over the past few decades has been negligible. Around 75% of the total volume of material released from creeks in Wolumla catchment since 1865, i.e., 5500 x 103 m3, has been derived from channel incision into valley fills at the base of the escarpment. Sediment flushing occurred within a few decades of catchment disturbance. Bedrock confinement in the middle and lower catchment resulted in very efficient downstream transfer of materials. Although gully networks and channel expansion sites have released a relatively small volume of material, these sources are the greatest contemporary source of sediment in Wolumla catchment.

Original languageEnglish
Pages (from-to)41-63
Number of pages23
Issue number1
Publication statusPublished - Mar 1999


  • Channel incision
  • Human impact
  • NSW
  • Sediment sources
  • Slope-channel coupling

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