Seabed sediment transport pathway investigations: review of scientific approach and methodologies

Velegrakis, Adonis F.; Collins, Michael B.; Bastos, Alex Cardoso; Paphitis, D.; Brampton, A.

doi:10.1144/gsl.sp.2007.274.01.13

Cited by 7 publications

(5 citation statements)

References 68 publications

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“…In accordance with the relationship between asymmetry and the direction of dune migration (McCave and Langhorne, 1982;Van Wesenbeck and Lanckneus, 2000;Velegrakis et al, 2007), the secondary dunes on the two slopes of the host dune migrate toward the host dune crest. This supports the theory of vertical circulation cells over dunes (Hulscher, 1996;Tonnon et al, 2007).…”

Section: Bedform Superimpositionmentioning

confidence: 70%

An automated procedure to calculate the morphological parameters of superimposed rhythmic bedforms

Wang

Zhang

et al. 2020

Earth Surf Processes Landf

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Subaqueous dunes are often observed to be superimposed on larger dunes, sand bars and tidal ridges, while smaller dunes may also be found superimposed on larger dunes. In this study an automated method has been developed by which the geometry of superimposed rhythmic bedforms can be analysed. The method combines two-dimensional (2D) Fourier analysis, wavelet transform, zero-crossing analysis and a variety of filters. Instead of applying conventional manual procedures, the wavelength of interest can be automatically determined by a series of 2D Fourier analyses, which is a critical first step for automated analysis of dune geometries. Based on such efficient data preprocessing, the method can accurately determine dune orientation, separate target bedform profiles, and identify crests and troughs. With the input of bathymetry, the dominant regional dune orientation can be determined together with the geometric parameters of individual dunes (wavelength, height, leeside angles) and their spatial distribution. The method was applied to both synthetic and observed bathymetries of a tidal ridge off the Jiangsu coast, China, and a sand bank in the Dover Strait, UK. The results show that almost all dunes in the domain were detected and their geometric parameters accurately calculated, especially in areas of bedform superimposition.

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Section: Bedform Superimpositionmentioning

confidence: 70%

An automated procedure to calculate the morphological parameters of superimposed rhythmic bedforms

Wang

Zhang

et al. 2020

Earth Surf Processes Landf

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“…Sediment tracer studies (both artificial, Black et al., 2007; Bosnic et al., 2017; Elias et al., 2011, and natural, Hein et al., 2013; McGann et al., 2013; Reimann et al., 2015; Rosenbauer et al., 2013; Wong et al., 2013) offer a Lagrangian technique for identifying pathways but are challenging to execute and recover (Elias et al., 2011). Grain trend analysis (Duc et al., 2016; Gao & Collins, 1991; Le Roux & Rojas, 2007; McLaren, 2013; McLaren & Bowles, 1985; McLaren et al., 1998; Poizot et al., 2006, 2008; Velegrakis et al., 2007) and analysis of bedform asymmetry (Barnard, Erikson, et al, 2013; Bartholdy et al., 2002; Sha, 1989; Velegrakis et al., 2007) offer additional techniques for identifying sediment pathways. However, field measurements alone are generally too limited to quantify sediment connections on the timescales of typical interest for engineering and policy decisions.…”

Section: Methodsmentioning

confidence: 99%

Sediment Connectivity: A Framework for Analyzing Coastal Sediment Transport Pathways

et al. 2020

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Connectivity provides a framework for analyzing coastal sediment transport pathways, building on conceptual advances in graph theory from other scientific disciplines. Connectivity schematizes sediment pathways as a directed graph (i.e., a set of nodes and links). This study presents a novel application of graph theory and connectivity metrics like modularity and centrality to coastal sediment dynamics, exemplified here using Ameland Inlet in the Netherlands. We divide the study site into geomorphic cells (i.e., nodes) and then quantify sediment transport between these cells (i.e., links) using a numerical model. The system of cells and fluxes between them is then schematized in a network described by an adjacency matrix. Network metrics like link density, asymmetry, and modularity quantify system-wide connectivity. The degree, strength, and centrality of individual nodes identify key locations and pathways throughout the system. For instance, these metrics indicate that under strictly tidal forcing, sand originating near shore predominantly bypasses Ameland Inlet via the inlet channels, whereas sand on the deeper foreshore mainly bypasses the inlet via the outer delta shoals. Connectivity analysis can also inform practical management decisions about where to place sand nourishments, the fate of nourishment sand, or how to monitor locations vulnerable to perturbations. There are still open challenges associated with quantifying connectivity at varying space and time scales and the development of connectivity metrics specific to coastal systems. Nonetheless, connectivity provides a promising technique for predicting the response of our coasts to climate change and the human adaptations it provokes. Plain Language Summary The pathways that sand takes as it moves along coasts and estuaries are determined by a complex combination of waves, tides, geology, and other environmental or human factors. These pathways can be challenging to analyze and predict using existing approaches, so we turn to the concept of connectivity. Connectivity represents the pathways that sediment takes as a series of nodes and links, much like in a subway or metro map. This approach is well used in other scientific fields, but in this study we apply these techniques to a new research field: coastal sediment dynamics. To demonstrate the sediment connectivity approach, we use it to map sediment pathways at a coastal site in the Netherlands. The statistics computed using connectivity let us quantify and visualize these sediment pathways, revealing new insights into the coastal system. We can also use this approach to address practical engineering questions, such as where to place sand nourishments for coastal protection. Sediment connectivity thus provides a promising technique for predicting the response of our coasts to climate change and the human adaptations it provokes.

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“…Generally, the alongshore distribution of the grain size parameters did not show any clear trends during the monitoring period. Only in June 2004, a westwards-fining trend appeared to be combined with a sorting improvement in the same direction at the area between Stations c and e, inferring westward sediment transport in the area west of the Chalandra River mouth (Gao and Collins, 1992;Velegrakis et al, 2007a). The absence of alongshore trends suggests that either the cross-shore transport of beach sediments is more important than its alongshore counterpart, or the sediment supply by the Chalandra River mouth to the middle section of Eressos Beach destroys alongshore trends (Flemming, 1988).…”

Section: Influence Of Dams On Downstream Beaches 359mentioning

confidence: 99%

Influence of Dams on Downstream Beaches: Eressos, Lesbos, Eastern Mediterranean

Velegrakis

Vousdoukas

Andreadis

et al. 2008

Marine Georesources & Geotechnology

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Small water storage dams are nowadays regarded as the ideal solution for the waterthirsty islands of the Greek Archipelago. Several of these dams have been already constructed and more are planned for the near future. However, dams can also create problems to coastal areas, particularly to the beaches found at the lower reaches of the dammed rivers. The present contribution reports the results of a study undertaken on the effects of such a dam located at Eressos, Lesbos (E. Mediterranean), using both morphological and sedimentological information and a GIS-based sediment erosion model. The results showed that Eressos Beach is currently under erosion, which however is spatially variable. The spatial variability of the beach erosion can only partly be explained by the patterns of longshore sediment transport, suggesting also a negative sedimentary balance. The results of the sediment erosion model showed that the dam retains more than half of the sediment produced in the basin, irrespective of the scenario used. Thus, it is likely that the effects of the dam on the downstream beach are already apparent.

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Seabed sediment transport pathway investigations: review of scientific approach and methodologies

Cited by 7 publications

References 68 publications

An automated procedure to calculate the morphological parameters of superimposed rhythmic bedforms

An automated procedure to calculate the morphological parameters of superimposed rhythmic bedforms

Sediment Connectivity: A Framework for Analyzing Coastal Sediment Transport Pathways

Influence of Dams on Downstream Beaches: Eressos, Lesbos, Eastern Mediterranean

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