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Seminar: Esther Eke

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December 14, 2012 @ 11:00 am - 12:00 pm

“Modeling channel width selection in meandering rivers”

 

Presented by: Esther Eke, Ph.D. Candidate in CEE at the University of Illinois at Urbana-Champaign

Abstract

Understanding the nature of morphologic changes of meandering rivers has long attracted the attention of the scientific community, in the fields of fluvial geomorphology, hydraulic engineering and river restoration. Several meander evolution models developed over the years have provided a deeper insight into meander dynamics. In almost all these models however, a river width that remains constant in space and in time is imposed as a user-specified parameter, without any consideration of the processes that establish this width. Consistent width variation patterns found in most meandering rivers (e.g.  Brice, 1982; Lagasse et al., 2004) are largely ignored by these models. Perhaps even more importantly, the questions as to how river width is selected and how width variation interacts with meander evolution remain unanswered.

The overarching questions surrounding this present research are: Is there a physics behind river width selection? Can we incorporate this physics (if it exists) to yield better prediction of meandering patterns? To answer these questions, we implement a recently proposed model for meander migration (e.g. Parker et al, 2011, Eke et al, 2011) to explore the general tendencies for channel migration and width evolution in a freely meandering system. In this model both bank processes (i.e. bank erosion and deposition) are considered independently, interacting through the medium of the channel in between. Bank erosion is modeled as erosion of purely non-cohesive material damped by natural armoring due to basal slump blocks, and channel deposition is modeled as a function of vegetal encroachment. Since banks are allowed to move independently, channel width is allowed to vary locally as a result of differential bank migration. Not only is this model useful to examine width selection in straight channels, it is also useful in examining spatial width variation tendencies in meandering systems.

Presently, the model has been formulated such that channel bank properties such as default vegetal encroachment rate, thickness of vegetated cohesive layer and characteristic slump block lifetime are specified constants. We illustrate co-evolving planform and width variation up to and beyond cutoff. Future work will include a floodplain component that explicitly models transport and overbank deposition of wash load (i.e. floodplain material).  This component is needed to account for river-floodplain interaction.

Biography

Esther Eke received a B.S. degree in Civil Engineering from the University of Lagos, Nigeria and a M.S. degree in Civil and Environmental Engineering from the University of Illinois at Urbana-Champaign (UIUC). She is currently finishing a Ph.D. in Civil and Environmental Engineering at UIUC. Her research interests include sediment transport and river morphodynamics, stream restoration, submarine sedimentation processes and delta morphodynamics. When not doing research, Esther enjoys outdoor activities, listening to music, and reading.

Details

Date:
December 14, 2012
Time:
11:00 am - 12:00 pm

Venue

Stanley Hydraulics Lab
100 SHL
Iowa City, IA 52242 United States
Phone:
319-335-5237
Posted on November 28th, 2012

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