Fangfang Zhu
The morphodynamics of a swash event on an erodible beach
Zhu, Fangfang; Dodd, Nicholas
Abstract
A high-accuracy numerical solution, coupling one-dimensional shallow water and bed-evolution equations, with, for the first time, a suspended sediment advection equation, thereby including bed and/or suspended load, is used to examine two swash events on an initially plane erodible beach: the event of Peregrine & Williams (J. Fluid Mech., vol. 440, 2001, pp. 391–399) and that of a solitary wave approaching the beach. Equations are solved by the method of characteristics, and the numerical model is verified. Full coupling of suspended load to beach change for Peregrine & Williams (J. Fluid Mech., vol. 440, 2001, pp. 391–399) yields only slightly altered swash flows, depending on beach mobility and sediment response time; a series of similar final beach change patterns results for different beach mobilities. Suspended- and bed-load transport have distinct morphodynamical signatures. For the solitary wave a backwash bore is created (Hibberd & Peregrine, J. Fluid Mech., vol. 95, 1979, pp. 323–345). This morphodynamical bore propagates offshore initially, and leads to the creation of a beach bed step (Larson & Sunamura, J. Sedimentary Petrology, vol. 63, 1993, pp. 495–500), primarily due to bed-load transport. Its height is directly related to bed-load mobility, and also depends strongly on the bed friction coefficient. The shock dynamics of this bed step is explained and illustrated. Bed- and suspended-load mobilities are quantified using field data, and an attempt is made to relate predictions to measurements of single swash events on a natural beach. Average predicted bed change magnitudes across the swash are of the order of 2 mm, with maximum bed changes of up to approximately 10 cm at the bed step.
Citation
Zhu, F., & Dodd, N. (2015). The morphodynamics of a swash event on an erodible beach. Journal of Fluid Mechanics, 762, https://doi.org/10.1017/jfm.2014.610
Journal Article Type | Article |
---|---|
Acceptance Date | Oct 17, 2014 |
Online Publication Date | Dec 2, 2014 |
Publication Date | Jan 1, 2015 |
Deposit Date | Jul 14, 2016 |
Publicly Available Date | Mar 29, 2024 |
Journal | Journal of Fluid Mechanics |
Print ISSN | 0022-1120 |
Electronic ISSN | 1469-7645 |
Publisher | Cambridge University Press |
Peer Reviewed | Peer Reviewed |
Volume | 762 |
DOI | https://doi.org/10.1017/jfm.2014.610 |
Keywords | coastal engineering, sediment transport, shallow water flows |
Public URL | https://nottingham-repository.worktribe.com/output/987595 |
Publisher URL | http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9444627&fileId=S0022112014006107 |
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