A morphogenic approach to world shorelines

Davies, J.L.

doi:10.1127/zfg/mortensen/8/1964/127

Cited by 416 publications

(60 citation statements)

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“…Active gravel beaches are studied from S Wales, where there is a macrotidal range and where wave energy is usually moderate, but where storms can be severe; Scotland, where there are macrotidal ranges, where wave energy is low and storms can be severe; and southern Namibia, where there is a microtidal range, the wave energy is always high (de Decker 1988) and storms are fairly severe (Davies 1964) (see Fig. 2).…”

Section: Zones Of Clast Shape-sizementioning

confidence: 99%

Clast assembling, bed-forms and structure in gravel beaches

Bluck

1998

Transactions of the Royal Society of Edinburgh: Earth Sciences

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Both textural maturity and structure acquired by gravels on beaches are largely a response to the interaction between beach surface and wave-backwash energy. The turbulent energy driving the processes of particle rejection andselection at the surface of growing gravel sheets is partly controlled by the grain size of the sheet itself, so the process is to a large extent self-regulating. Beach surfaces are seen to comprise many discrete sheets of gravel competing for growth at their boundaries, but each characterised by a uniform or uniformly gradational texture.There are two main types of gravel sheet: (1) selection pavements which occur on low beach slopes, showing little areal grain-size or grain-shape variation, and (2) turbulence shadows which occur on steeper slopes and produce assemblages of clasts which may show perfect lateral shape and size gradation.The clasts which make up these various gravel sheets are termed ‘clast assemblages’, and such assemblages are the fundamental units from which beaches are constructed. Clast assemblages are classified in terms of their textural maturity—the degree to which they exhibit uniformity in clast size and shape. In beach sections they are, either singly or in combination, bounded by planes of discontinuity (bedding planes) to form beds.Repeated combinations of either clast assemblages or beds in a genetic association are regarded as sedimentary structures, many of which are diagnostic of the gravel beach environment. Growth of beaches involves the stacking of sedimentary structures, and four growth patterns have been identified. The beach structure is, therefore, classified in a hierarchy comprising clast assemblage, bed, structures and growth form, and it is the growth pattern which may be related to tidal range. P.ecognition of the processes which generate beach gravels through the structure of the gravels permits an analysis of the internal structure of major gravel bodies such as barrier beaches. It adds another set of criteria which may further lead to an understanding of the processes responsible for the generation and evolution of these large gravelforms.Three types of gravel lithosomes have been identified. (1) Regressive barrier bars which form a series of gravel ridges separated by lagoonal deposits. Barriers are built initially by swash bars which grow in size and coarsen through time to become wave-resistant forms. They form as a response to times when the sediment, unable to be evenly distributed and sorted on the beach surface, forms a discrete bar seaward of the active beach. This is the result of a punctuated or continuously high sediment supply compared with the wave energy available to disperse the sediment, or a falling sea level which shifts the locus of sediment accretion. (2) In contrast, regressive (prograding) gravel sheets form as a response to a continuous supply of sediment to the beach surface, allowing it to build seaward by the uniform accretion of sediment which is sorted and retained on its surface. (3) Gravel sheets produced in transgression are characterised by an abundance of spherical clasts and are often overlapped by the sand beaches which occur seaward of them.

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Section: Zones Of Clast Shape-sizementioning

confidence: 99%

Clast assembling, bed-forms and structure in gravel beaches

Bluck

1998

Transactions of the Royal Society of Edinburgh: Earth Sciences

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“…Keansburg experiences semi-diurnal tides with a Great Diurnal Range of 1.66 m and mean range of 1.5 m (mean higher high water [MHHW] 0.77 m NAVD; MLLW −0.89 m NAVD). Consequently, the site can be classified as micro-tidal; tidal driven currents in microtidal shorelines are not expected to govern shoreline morphology [32]. The spring and neap tidal prism have been estimated to be 3.8 × 10 5 m 3 and 3.4 × 10 5 m 3 , respectively.…”

Section: Meteorologic and Hydraulic Characteristicsmentioning

confidence: 99%

Mitigation of Channel Shoaling at a Sheltered Inlet Subject to Flood Gate Operations

Lemke

Janssen

Miller

2020

JMSE

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A comprehensive case study of Keansburg Inlet (New Jersey, USA) is presented with the objective of evaluating inlet management alternatives and assessing the influence of an operational flood gate on channel shoaling. The goal of the research is determining the most effective strategy for minimizing the frequency of maintenance dredging. This study compares the effectiveness of (1) traditional structural solutions; (2) modified dredging templates; and (3) assesses the influence of the flood gate operations during conditions representative of a typical year. Alternative analysis is completed using a coupled hydrodynamic–wave model (Delft3D-Flexible Mesh (FM)) with Real Time Control to simulate morphological changes. The model was calibrated and evaluated using collected field data. Water levels are reproduced within 6% of the spring tide range with lag times less than 20 min. The model results and observations suggest sediment transport is dominated by wave action with pronounced variations in dominant wave direction. The results indicate that changes to the operational dredging, or what the authors have termed broadly as “adaptive dredging techniques”, appear to deliver the most promising improvement. Model results suggest that the current operational procedures of the flood gate do not significantly alter the channel infilling rates and patterns during typical (i.e., non-extreme event) conditions.

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“…The Yellow Sea is dominated by a semi-diurnal tide, with the M 2 tide being the predominant tidal constituent (Choi, 1980;Fang, 1986;Lee and Beardsley, 1999). The "radial sand ridges" are located on the inner-shelf of the South-Western Yellow Sea with a mean tidal range of 4-6 m (Ren et al, 1986) and can be thus classified as a macro-tidal area (Davies, 1964). The largest observed tidal range can be up to 9.28 m in the Huangshayang tidal channel (Wang et al, 2012).…”

Section: Regional Settingmentioning

confidence: 99%

Dynamics of a Tidal Current System in a Marginal Sea: A Case Study of the Yellow Sea, China

Zhang

Yao

et al. 2020

Front. Mar. Sci.

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Tidal currents belong to the main driving forces shaping the bathymetry of marginal seas. A globally unique radial sand ridge field exists in the South Yellow Sea off the central Jiangsu coast, China. Its formation is related to the distinctive “radial tidal current” pattern at that location. A generally accepted hypothesis is that the “radial tidal current” is a consequence of the interference between the northern amphidromic tidal wave system and the southern incoming tidal wave. In this study, a schematized numerical tidal model was designed to investigate the tidal current system and the factors of influence in the South Yellow Sea. Concepts of the tidal current amphidromic point (CAP) and the tidal current inclination angle are utilized to analyze the inherent structure of the tidal current system. By conducting a series of numerical experiments, it is found that the Poincaré modes are necessary for the existence of “radial tidal current,” and the e-folding decay length should be smaller than the basin length. In the Yellow Sea, cross-basin phase differences due to lateral depth differences as well as open boundary conditions favor the emergence of the “radial tidal current.” Further analyses indicate that the CAP system (i.e., the co-inclination lines, the CAPs, and the tidal ellipticity) deepens the understanding on the dynamic structure of a tidal current system, and therefore, it deserves more attention in future studies.

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A morphogenic approach to world shorelines

Cited by 416 publications

References 0 publications

Clast assembling, bed-forms and structure in gravel beaches

Clast assembling, bed-forms and structure in gravel beaches

Mitigation of Channel Shoaling at a Sheltered Inlet Subject to Flood Gate Operations

Dynamics of a Tidal Current System in a Marginal Sea: A Case Study of the Yellow Sea, China

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