Buscombe,D. and Masselink,G.(2006): Concepts in gravel beach dynamics. Earth-Science Reviews, 79, 33-52.

『礫海岸ダイナミクスにおける概念』


Abstract
 The dominant processes in gravel beach dynamics are reviewed, highlighting some common themes which unify the various components of the gravel beach system, the repercussions of which impart on how gravel beach dynamics might be understood conceptually. In particular, gravel beach dynamics are thought to be highly dependent on the temporal and spatial variation in grain size, and the continual adjustments made by an active beach step, both of which act not only as the expression of changing morphodynamic conditions, but also as a controlling influence. Morphodynamics, the notion that the exchanges on beaches between the hydrodynamics, sediment transport, and morphological changes takes the form of reciprocal relationships which are mediated through feedback mechanisms (in such a way that they cannot be thought of or studied independently) is not a new one. Yet it appears that for the gravel beach, morphodynamics must be re-defined to describe conditions where variations in sediment size are thought to deserve parity, rather than as merely a sequent entity or boundary condition. ‘Morpho-sedimentary-dynamics’ is a phrase coined to intuit such cause and effect, detailing the co-evolution of morphology, hydro-hydraulics and sediment properties whilst acknowledging causative pluralism, feedbacks and multiplier effects. This is the recommended conceptual framework within which to crystallise thought and organise further research for the gravel beach. Essentially, it increases the minimum number of parameters needed to describe the state of the gravel beach as a physical system. Therefore, it is advised that simplicity will be most expedient in our future modelling efforts, if complexity is to be adequately encapsulated.


Keywords: Coastal geomorphology; Gravel beaches; Nearshore sediment transport; Sedimentology』

1. Introduction
2. Hydrodynamics and sediment transport
 2.1. Hydrodynamics
 2.2. Swash-groundwater hydraulic exchange and sediment transport
 2.3. Transport mode
3. Textural mosaics
 3.1. Sorting and grading
 3.2. Longshore sediment transport
 3.3. Conventional sorting coefficients
4. Morphological features
 4.1. Step and foreshore dynamics
 4.2. Cusps
 4.3. Storm beach
5. Discussion
 5.1. Beach feature - analogues and ‘bedform surrogacy’
6. A conceptual framework for gravel beach research: Morpho-sedimentary dynamics
7. Suggestions for further work
 7.1. Behavioural modelling
 7.2. Probabilistic analysis
8. Conclusion
Acknowledgements
References


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