Sediment transport studies in the tidal basins of the Dutch Waddenzee

McLaren, Patrick; Steyaert, Frank; Powys, Richard I. L.

doi:10.1007/bf03043943

“…The ebb-tidal delta is primarily composed of sand, with the coarsest sand in the inlet channel and proximal parts of the ebb-delta channels (Sha, 1990; McLaren et al, 1998; Fig. 2).…”

Section: Study Areamentioning

confidence: 99%

“…2. Median grain sizes on Texel ebb-tidal delta. Depth contours indicate the 1992 bathymetry (see McLaren et al, 1998, for details on measurements). …”

Section: Study Areamentioning

confidence: 99%

Dynamic preservation of Texel Inlet, the Netherlands: understanding the interaction of an ebb-tidal delta with its adjacent coast

Elias

¹

,

Spek

²

2017

Netherlands Journal of Geosciences

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Tidal inlets and the associated ebb-tidal deltas can significantly impact the coastal sediment budget due to their ability to store or release large quantities of sand. Nearly 300 million m3(mcm) of sediments were eroded from Texel Inlet's ebb-tidal delta and the adjacent coasts following the closure of the Zuiderzee in 1932. This erosion continues even today as a net loss of 77 mcm was observed between 1986 and 2015. To compensate, over 30 mcm of sand has been placed on the adjacent coastlines since 1990, making maintenance of these beaches the most intensive of the entire Dutch coastal system.Highly frequent and detailed observations of both the hydrodynamics and morphodynamics of Texel Inlet have resulted in a unique dataset of this largest inlet of the Wadden Sea, providing an opportunity to investigate inlet sediment dynamics under the influence of anthropogenic pressure. By linking detailed measurements of bathymetric change to direct observations of processes we were able to unravel the various components that have contributed to the supply of sediment to the basin, and develop a four-stage conceptual model describing the multi-decadal adaptation of the ebb-tidal delta.Prior to closure of the Zuiderzee a dynamic equilibrium state (stage 1) existed with a stable ebb-tidal delta. The largest morphological changes occurred in roughly the first 40 years since the closure, and were dominated by the rotation and scouring of large tidal channels and landward retreat of the Noorderhaaks ebb shoal (stage 2; adaptation). Between 1975 and 2001 the general layout of main channels and shoals was stable, but large sediment losses continued to occur (stage 3; equilibrium erosional state). Since 2001, the erosion rates have significantly reduced to 2 mcm a−1(stage 4; stabilisation).Twenty-five years of data on ‘Dynamic Preservation’ prove that sand nourishments are well capable of keeping the coastlines adjacent to the Texel Inlet in place. Moreover, the abundant supply of sediment may also have compensated for the sediment losses on the larger scale of the southern part of the ebb-tidal delta, resulting in a recent stabilisation of its volume. This response illustrates the potential benefits of Dynamic Preservation not only for coastline resilience but also on the larger scale of the inlet system. Such knowledge is essential for future preservation, management and maintenance of inlet systems in the scope of climate change and accelerated sea-level rise.

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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

Pearson

¹

,

Prooijen

²

,

Elias

³

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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“…Sediment tracer studies (both artificial, Black et al, 2007;Bosnic et al, 2017;Elias et al, 2011, andnatural, 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, 2006Poizot et al, , 2008Velegrakis et al, 2007) and analysis of bedform asymmetry 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: Developing a Networkmentioning

confidence: 99%

Sediment Connectivity: A Framework for Analyzing Coastal Sediment Transport Pathways

Pearson

¹

,

Prooijen

²

,

Elias

³

et al. 2020

Preprint

View full text Add to dashboard Cite

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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Sediment transport studies in the tidal basins of the Dutch Waddenzee

Cited by 7 publications

References 3 publications

Dynamic preservation of Texel Inlet, the Netherlands: understanding the interaction of an ebb-tidal delta with its adjacent coast

Dynamic preservation of Texel Inlet, the Netherlands: understanding the interaction of an ebb-tidal delta with its adjacent coast

Sediment Connectivity: A Framework for Analyzing Coastal Sediment Transport Pathways

Sediment Connectivity: A Framework for Analyzing Coastal Sediment Transport Pathways

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