Hydraulic resistance of artificial vegetation patches in aligned and staggered configurations

Mario Savio, Davide Vettori* (Corresponding Author), Hamish Biggs, Andrea Zampiron, Stuart M. Cameron, Mark Stewart, Chris Soulsby, Vladimir Nikora

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)
1 Downloads (Pure)


The paper reports the results of laboratory experiments to investigate the effect of vegetation patch mosaics on hydraulic resistance. Experiments were run for seven levels of vegetation coverage with square patches of flexible plastic grass in aligned and staggered configurations and a wide range of hydraulic conditions. Hydraulic resistance was substantially higher for staggered than aligned configurations, particularly for intermediate ranges of vegetation coverage. The results indicate that hydraulic resistance differs between regimes of isolated roughness flow, wake interference flow, and skimming flow. Two types of models are proposed to predict hydraulic resistance (i.e. Manning’s coefficient n) for aligned and staggered configurations, one as a function of the nondimensional spatially-averaged hydraulic radius and another as a function of relative submergence and surface area blockage factor. To account for the effects of vegetation patch alignment, an additional factor α is introduced. This work provides comprehensive datasets and models that can be used to improve the prediction of hydraulic resistance in open-channel flows with vegetation patches.

Original languageEnglish
Pages (from-to)220-232
Number of pages12
JournalJournal of Hydraulic Research
Issue number2
Early online date26 Apr 2023
Publication statusE-pub ahead of print - 26 Apr 2023

Bibliographical note

The study has been supported by three EPSRC/UK grants (Engineering and Physical Sciences Research Council): “High-resolution numerical and experimental studies of turbulence-induced sediment erosion and near-bed transport” (EP/G056404/1), “Bed friction in rough-bed free-surface flows: a theoretical framework, roughness regimes, and quantification” (EP/K041088/1) and “Secondary currents in turbulent flows over rough walls” (EP/V002414/1).

Publisher Copyright:
© 2023 International Association for Hydro-Environment Engineering and Research.


  • Ecohydraulics
  • environmental fluid mechanics
  • flow–biota interactions
  • hydraulic resistance
  • vegetated flows


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