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Field and laboratory observations of small-scale dispersion in wetlands

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dc.contributor.advisor Heidi M. Nepf. en_US Lightbody, Anne F. (Anne Fraser), 1977- en_US
dc.contributor.other Massachusetts Institute of Technology. Dept. of Civil and Environmental Engineering. en_US 2005-10-14T20:13:15Z 2005-10-14T20:13:15Z 2004 en_US 2004 en_US
dc.description Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2004. en_US
dc.description Includes bibliographical references (p. 156-160). en_US
dc.description.abstract Estimating longitudinal dispersion in wetlands is a necessary first step in predicting the behavior of dissolved species and suspended particles. However, many processes are involved, and they can interact in nonlinear ways. Relevant processes include turbulent diffusion, which describes net solute flux created by turbulent eddies. Other dispersive processes result from the retardation of a portion of the solute relative to the rest of a cloud. This retardation can be provided by trapping in the vortex structure behind stems (hold-up dispersion), velocity deficits well downstream of stems (stem-wake dispersion), or transverse gradients in longitudinal velocity (shear dispersion). To better understand the relative magnitude of these various dispersive processes, measurements were taken of velocity, vertical diffusion, and longitudinal dispersion in both the laboratory and the field. Laboratory flume experiments were conducted using an emergent canopy of rigid cylinders with different cylinder densities over depth. Field experiments were conducted in a natural salt marsh. Drag due to local stem density was found to control horizontal velocity in both the lab and field studies over most of the depth. The resulting non-uniform velocity profile generated shear dispersion, which controlled dispersion at longer distances (> 250 cm) downstream of a slug release. For distances < 250 cm downstream, wake shear dispersion was found to be most important. en_US
dc.description.statementofresponsibility by Anne F. Lightbody. en_US
dc.format.extent 173 p. en_US
dc.format.extent 6215149 bytes
dc.format.extent 6214954 bytes
dc.format.mimetype application/pdf
dc.format.mimetype application/pdf
dc.language.iso eng en_US
dc.publisher Massachusetts Institute of Technology en_US
dc.rights M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. en_US
dc.subject Civil and Environmental Engineering. en_US
dc.title Field and laboratory observations of small-scale dispersion in wetlands en_US
dc.type Thesis en_US S.M. en_US
dc.contributor.department Massachusetts Institute of Technology. Dept. of Civil and Environmental Engineering. en_US
dc.identifier.oclc 56124790 en_US

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