Controls on the distribution of channel reach morphology in selectively glaciated catchments

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To assess the controls on the distribution of channel reach morphology in a selectively glaciated landscape, we used field mapping and a geographical information system (GIS) in the River Dee catchment, northeast Scotland. Controls on channel morphology were investigated using (1) continuous longitudinal assessment of channel morphology distribution in relation to geology, glacial history, topography, and total stream power (Ω) in two subcatchments, and (2) slope (S), Ω, and a slope–drainage area (S–A) framework to understand the occurrence of 173 widely distributed bedrock, mixed bedrock–alluvial, and alluvial (three different types) reaches. The S–A framework used indicators of transport capacity (Qc) and sediment supply (Qs) to differentiate channel types. The study highlights the disjointed nature of channel reach distribution at the river scale that reflects variable lithology and glacial modification. Because of the subdued topography in contrast to other regions, colluvial forcing of channel morphology in the headwaters was lacking. However, in common with other glaciated landscapes, repeated sequences of channel reach type progression determined by valley steps were evident. The S–A analysis successfully discriminated 87.2% of alluvial and 91.4% of bedrock reaches despite the variable land use and glacial modification. Discrimination of the full range of channel types using S, Ω, or the S–A framework was poor however. Notably, a third of the transport alluvial reaches were located in the bedrock S–A domain, and the majority of mixed reaches were widely distributed mostly within the bedrock domain and not close to the critical slope (Sc). In comparison to other regions, the Sc above which Qc > Qs and bedrock reaches dominate, was notably higher. We hypothesise that a drier climate and the higher entrainment threshold of coarse, granite-dominated bed materials create a higher Sc.
Original languageEnglish
Pages (from-to)121-133
Number of pages13
Early online date8 Jan 2014
Publication statusPublished - 15 Apr 2014

Bibliographical note

This paper is based on a PhD project funded by the University of Aberdeen, 6th Century award scheme. Resources were supplied by the Geography and Environment department at the University of Aberdeen and the James Hutton Institute. Financial support during the preparation of this paper was given by the James Hutton Institute. We greatly thank numerous people who assisted with the field surveys and Dr. Luigi Spezi of BIOSS for advice on the statistical analysis. We also thank Dr. Sohan Ghimire, Dr. Francesco Brardinoni, and two anonymous reviewers for their constructive comments and Dr Richard Marston for editing the manuscript.


  • slope–area analysis
  • bedrock reaches
  • alluvial reaches
  • sediment supply
  • transport capacity
  • channel morphology


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