Bed drag coefficient variability under wind waves in a tidal estuary

Jeremy D. Bricker, Satoshi Inagaki, Stephen G. Monismith

Research output: Contribution to journalArticlepeer-review

30 Citations (Scopus)


In this paper we report the results of a study of the variation of shear stress and the bottom drag coefficient CD with sea state and currents at a shallow site in San Francisco Bay. We compare shear stresses calculated from turbulent velocity measurements with the model of Styles and Glenn reported in 2000. Although this model was formulated to predict shear stress under ocean swell on the continental shelf, results from our experiments show that it accurately predicts these bottom stress under wind waves in an estuary. Higher up in the water column, the steady wind-driven boundary layer at the free surface overlaps with the steady bottom boundary layer. By calculating the wind stress at the surface and assuming a linear variation of shear between the bed and surface, however, the model can be extended to predict water column shear stresses that agree well with data. Despite the fidelity of the model, an examination of the observed stresses deduced using different wave-turbulence decomposition schemes suggests that wave-turbulence interactions are important, enhancing turbulent shear stresses at wave frequencies. Journal of Hydraulic Engineering

Original languageEnglish
Pages (from-to)497-508
Number of pages12
JournalJournal of Hydraulic Engineering
Issue number6
Publication statusPublished - 2005 Jun 1


  • Drag coefficient
  • Estuaries
  • Hydraulic roughness
  • Tidal currents
  • Turbulence
  • Waves

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Water Science and Technology
  • Mechanical Engineering

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