Hydraulic resistance in mixed bedrock-alluvial meandering channels

Roberto Fernández, Alejandro J. Vitale, Gary Parker, Marcelo H. García

Research output: Contribution to journalArticlepeer-review


We present an experimental analysis of hydraulic roughness variations due to changes in alluvial cover in a mixed bedrock-alluvial meandering channel with larger bedrock roughness than alluvial roughness. Three sets of experiments were conducted in a highly sinuous flume: one with bare bedrock, and two with enough sediment to cover 21% and 78% of the bedrock respectively. We compare our results with data from experiments previously conducted in the same flume with flat- and smooth-bed, and data from experiments with fully alluvial conditions. Our results show that: (1) hydraulic resistance in a mixed bedrock-alluvial channel changes with the degree of alluviation; (2) hydraulic resistance is greater for bare-bedrock conditions, and decreases as sediment supply increases; (3) if bedforms appear, hydraulic resistance may be larger than for bare bedrock conditions due to form drag; (4) fluctuations in alluvial cover due to freely-migrating bars lead to instantaneous changes in hydraulic resistance.

Original languageEnglish (US)
Pages (from-to)298-313
Number of pages16
JournalJournal of Hydraulic Research
Issue number2
StatePublished - 2021


  • Alluvial cover
  • bars
  • bed roughness
  • bedforms
  • bedload
  • hydraulic resistance
  • meandering

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Water Science and Technology


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