Predicting the roughness length of turbulent flows over landscapes with multi-scale microtopography

Jon Pelletier, Jason P. Field

Research output: Contribution to journalArticle

9 Scopus citations


The fully rough form of the law of the wall is commonly used to quantify velocity profiles and associated bed shear stresses in fluvial, aeolian, and coastal environments. A key parameter in this law is the roughness length, z0. Here we propose a predictive formula for z0 that uses the amplitude and slope of each wavelength of microtopography within a discrete-Fourier-transform-based approach. Computational fluid dynamics (CFD) modeling is used to quantify the effective z0 value of sinusoidal microtopography as a function of the amplitude and slope. The effective z0 value of landscapes with multi-scale roughness is then given by the sum of contributions from each Fourier mode of the microtopography. Predictions of the equation are tested against z0 values measured in ∼ 105 wind-velocity profiles from southwestern US playa surfaces. Our equation is capable of predicting z0 values to 50% accuracy, on average, across a 4 order of magnitude range. We also use our results to provide an alternative formula that, while somewhat less accurate than the one obtained from a full multi-scale analysis, has an advantage of being simpler and easier to apply.

Original languageEnglish (US)
Pages (from-to)391-405
Number of pages15
JournalEarth Surface Dynamics
Issue number2
StatePublished - May 19 2016

ASJC Scopus subject areas

  • Earth-Surface Processes
  • Geophysics

Fingerprint Dive into the research topics of 'Predicting the roughness length of turbulent flows over landscapes with multi-scale microtopography'. Together they form a unique fingerprint.

  • Cite this