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Process-based modelling of bank-breaking mechanisms of tidal sandbanks

Veelen, T.J. van (2016) Process-based modelling of bank-breaking mechanisms of tidal sandbanks.

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Abstract:To improve our understanding of transient longterm plan view dynamics of tidal sandbanks, we have developed a nonlinear idealized morphodynamic model. Current mechanisms describe how an isolated bank breaks into multiple banks, but they lack process-based support.We aim to provide such support with the inclusion of nonlinear interactions between tidal flow, topography, Coriolis and bottom friction in the hydrodynamic formulation and depthdependent wind wave stirring and slope effects in the bedload sediment transport formulation. We distinguish three generic evolution paths. (I) Rotation of the bank ends towards the preferred angle of deposition and separate growth, causing bank-breaking. (II) Rotation of the bank ends towards the preferred angle of deposition and central growth, triggering an S-shape. (III) Straight outline and central growth, triggering an S-shape, but much faster than path II. In addition to the path-dependent dynamics, the banks also experience pattern expansion, elongation and amplitude growth. Bank-breaking (path I) requires two condition. The initial bank may not have an orientation in the angle of preferred deposition and must be sufficiently long to trigger separate growth. Alternatively, the nonlinear flow response to an elevated centre triggers evolution towards an S-shape. The proposed paths are consistent with mechanisms in Huthnance (1982b) and Smith (1988). The characteristic final Sshape shows resemblance to meandering banks in the North Sea.
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering and Management MSc (60026)
Link to this item:http://purl.utwente.nl/essays/74980
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