Comparison of vegetation roughness descriptions

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Vegetation roughness is an important parameter in describing flow through river systems. Vegetation impedes the flow, which affects the stage-discharge curve and may increase flood risks. Roughness is often used as a calibration parameter in river models, however when vegetation is allowed to develop naturally in river restoration projects, it is important to have suitable predictions of the increased resistance caused by the vegetation. There are many formulas available for describing vegetation roughness in one or two dimensional flow, ranging from simple wall roughness approximations to (semi-) empirical or theoretically derived roughness descriptions that are a function of flow and plant characteristics. In this paper a number of roughness descriptions are compared. All descriptions give a reasonable fit to experimental flume data. However, the models show significant deviation when extrapolating to large water depths typical for extreme discharge conditions. Therefore, to identify the suitability of existing methods for flood modeling, more data at large water depths are necessary. At large submergence ratios vegetation roughness can be approximated by a constant Manning coefficient.
Original languageUndefined
Title of host publicationProceedings of River Flow 2008 - Fourth International Conference on Fluvial Hydraulics, 3-5 September 2008 Çe¿me, Turkey.
EditorsM.S. Altinakar, M.A. Kokpinar, I. Aydin, S. Cokgor, S. Kirkgoz
Place of PublicationAnkara
PublisherKubaba Congress Department and Travel Services
Number of pages9
Publication statusPublished - 3 Sept 2008
EventRiver Flow 2008: 4th International Conference on Fluvial Hydraulics - Izmir, Turkey
Duration: 3 Sept 20085 Sept 2008

Publication series



ConferenceRiver Flow 2008


  • IR-60441
  • vegetation roughness
  • METIS-246788
  • River models
  • Uncertainty

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