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dc.contributor.authorHopkinson, Leslieen_US
dc.date.accessioned2014-03-14T21:22:38Z
dc.date.available2014-03-14T21:22:38Z
dc.date.issued2009-10-20en_US
dc.identifier.otheretd-10292009-111417en_US
dc.identifier.urihttp://hdl.handle.net/10919/40267
dc.description.abstractThis research is intended to determine the role of riparian vegetation in stream morphology. This experiment examined the effects of riparian vegetation on boundary shear stress (BSS) by completing the following objectives: (1) evaluating the effects of streambank vegetation on near-bank velocity and turbulence; (2) determining a method for measuring BSS; and, (3) examining the effects of streambank vegetation on BSS using an existing model. A second order prototype stream, with individual reaches dominated by the three vegetation types (trees, shrubs, and grass) was modeled using a fixed-bed Froude-scale modeling technique. One model streambank of the prototype stream was constructed for each vegetation type in addition to one bank with only grain roughness. Velocity profiles were measured using an acoustic Doppler velocimeter (ADV) and a miniature propeller (MP). A flush-mounted Dantec MiniCTA system was used to measure shear stress at the streambank wall. The addition of vegetation on a sloping streambank increased the streamwise free stream velocity and decreased the near-bank streamwise velocity. The turbulence caused by the upright shrub treatment increased turbulent kinetic energy and Reynolds stresses near the streambank toe, an area susceptible to fluvial erosion. The presence of dense, semi-rigid vegetation may encourage the formation of a wider channel with a vertical streambank. The small range of CTA shear stress measurements (0.02â 2.14 Pa) suggested that one estimate can describe a streambank. The law of the wall technique is not appropriate because the velocity profiles did not follow the necessary logarithmic shape. Vegetative roughness present in channels created secondary flow; turbulence characteristics more appropriately estimated BSS. The BSS model predicted velocity fields in similar distribution to that measured by the ADV and MP. BSS calculated using the ray-isovel method for both velocity measurement devices were different than the measured BSS values, likely due to distortions in the measured velocity field. In general, the predicted BSS distribution increased with water depth and decreased with increasing vegetation density. The predicted BSS at the shrub toe indicated a spike in shear stress consistent with TKE estimates.en_US
dc.publisherVirginia Techen_US
dc.relation.haspartHopkinson_LC_D_2009.pdfen_US
dc.rightsI hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Virginia Tech or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report.en_US
dc.subjectvegetated flowen_US
dc.subjectturbulent kinetic energyen_US
dc.subjectstreambank vegetationen_US
dc.subjectReynolds stressen_US
dc.subjectStreambank erosionen_US
dc.titleBoundary Shear Stress Along Vegetated Streambanksen_US
dc.typeDissertationen_US
dc.contributor.departmentBiological Systems Engineeringen_US
dc.description.degreePh. D.en_US
thesis.degree.namePh. D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplineBiological Systems Engineeringen_US
dc.contributor.committeechairWynn, Theresa M.en_US
dc.contributor.committeememberDolloff, C. Andrewen_US
dc.contributor.committeememberDancey, Clinton L.en_US
dc.contributor.committeememberDiplas, Panayiotisen_US
dc.contributor.committeememberHession, W. Cullyen_US
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-10292009-111417/en_US
dc.date.sdate2009-10-29en_US
dc.date.rdate2009-11-17
dc.date.adate2009-11-17en_US


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