Sediment transport, aqueous bedform stability and morphodynamics under unidirectional current: a brief overview

Mazumder, Rajat

doi:10.1016/s0899-5362(03)00018-6

Cited by 27 publications

(13 citation statements)

References 76 publications

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“…The later would typically show different degrees of deformation. It is also difficult to find the intricate pattern of branching and truncated undulations (Figures 2 and 3) in known subaereal and submarine failures, while it is quite common in current driven sediment structures such as ripples and aeolian sand dunes [e.g., Mazumder , 2003]. Wynn and Stow [2002] also point out that in planform view most sediment waves appear as linear features with varying degrees of sinuosity and/or bifurcation while creep/slump folds are arcuate and do not show bifurcation [e.g., Kenyon et al , 1978].…”

Section: Interpretation and Discussionmentioning

confidence: 99%

Sediment undulations on the Llobregat prodelta: Signs of early slope instability or sedimentary bedforms?

Úrgeles¹,

Mol²,

Liquete³

et al. 2007

J. Geophys. Res.

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[1] A field of sediment undulations has been mapped by means of high-resolution multibeam bathymetry and seismic reflection profiles in the Llobregat River prodelta, off the city of Barcelona, Catalonia, Spain. Similar features had previously been recognized in other prodelta environments and interpreted either as downslope sediment deformation or sedimentary structures induced by bottom currents or hyperpycnal flows. Since the study area is undergoing significant offshore development, proper interpretation of such sediment undulations is needed for a correct risk assessment. The occurrence of the sediment undulations is restricted to the prodelta front on slope gradients between 3 and 0.2°. The undulations have developed at the edge and atop an area of gas bearing sediments within the Late Holocene high-stand mud wedge. An evaluation is made of the characteristics of the sediment undulations in order to determine the most likely process for the origin of these structures. Among these characteristics are the continuity of the reflections and lack of diffractions in between different undulations, their size distribution (large to small) both from shallow to deep and with depth in section, the asymmetry (decreasing from proximal to distal), the crest to trough vertical distance on the landward side of the undulations (up to 0.5 m), and the lack of features that could indicate a progressive movement such as growth structures and drag folds. These characteristics indicate that the sediment undulations on the Llobregat River prodelta do not result from sediment deformation but rather from the interaction of bottom currents generated by hyperpycnal flows from the Llobregat River with regional sea water circulation. Their identification as sediment waves implies that such features do not pose a major hazard for further offshore development.

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Section: Interpretation and Discussionmentioning

confidence: 99%

Sediment undulations on the Llobregat prodelta: Signs of early slope instability or sedimentary bedforms?

Úrgeles¹,

Mol²,

Liquete³

et al. 2007

J. Geophys. Res.

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“…Regime diagrams have been used to quantify the physical controls on the formation, stability and morphodynamics of bedforms and channel types (Mazumder, 2003). Process-based regime diagrams have been applied to mountain channels using proxies for Q c and Q s based on reach D 50s and the Meyer-Peter-Muller (1948) (MPM) equation (Buffington et al, 2003;Thompson et al, 2006):…”

Section: Contribution Of Regime Diagrams To a Process Differentiationmentioning

confidence: 99%

Channel flow competence and sediment transport in upland streams in southeast Australia

Thompson

Croke

2007

Earth Surf Processes Landf

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Bedload transport data from planebed and step-pool reach types are used to determine grain size transport thresholds for selected upland streams in southeast Australia. Morphological differences between the reach types allow the effects of frictional losses from bedforms, microtopography and bed packing to be incorporated into the dimensionless critical shear stress value. Local sediment transport data are also included in a regime model and applied to mountain streams, to investigate whether empirical data improve the delineation of reach types on the basis of dimensionless discharge per unit width (q*) and dimensionless bedload transport (q b *). Instrumented planebed and step-pool sites are not competent to transport surface median grains (D 50s ) at bankfull discharge (Q bf ). Application of a locally parametrized entrainment equation to the full range of reach types in the study area indicates that the majority of cascades, cascade-pools, step-pools and planebeds are also not competent at Q bf and require a 10 year recurrence interval flood to mobilize their D 50s . Consequently, the hydraulic parameters of the regime diagram, which assume equilibrium conditions at bankfull, are ill suited to these streams and provide a poor basis of channel delineation. Modifying the diagram to better reflect the dominant transported bedload size (equivalent to the D 16 of surface sediment) made only slight improvements to reach delineation and had greatest effect on the morphologies with smaller surface grain sizes such as forced pool-riffles and planebeds. Likewise, the Corey shape factor was incorporated into the regime diagram as an objective method for adjusting a base dimensionless critical shear stress (τ τ τ τ τ * c50b ) to account for lithologically controlled grain shape on bed packing and entrainment. However, it too provided only minor adjustments to reach type delineation. the ratio between sediment transport capacity (Q c ) and sediment supply (Q s ) (Montgomery and Buffington, 1997). Subsequent refinement of the Q c /Q s model introduced the concept of different supply-transport domains, which were

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“…This may be due to (Ashley, 1990;Terwindt, 1971). They are good indicators for hydrological conditions as they are controlled by flow depth, grain size, current velocity and direction (Ashley, 1990;Mazumder, 2003;Rubin & Mcculloch, 1980). As sediment transport and water flow and speed varies both spatially and temporally, this has given rise to various bedform sizes and morphologies and a wide range of nomenclature.…”

Section: Submerged Landformsmentioning

confidence: 99%

Geomorphology and substrate of Galway Bay, Western Ireland

McCullagh¹,

Benetti²,

Plets

et al. 2020

Journal of Maps

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A combination of multibeam bathymetry and backscatter, LiDAR altimetry and bathymetry, satellite images, and hydrodynamic model outputs were used to map the seafloor and coastline of Galway Bay (western Ireland). This is the first time these multiple datasets have been integrated into a single combined geomorphological and substrate map. The substrate of the bay is predominantly mud and sand with bedrock outcropping extensively around the coastline. The main depositional features are dunes, while the main erosional features are scours and outcropping bedrock. Hydrodynamic model outputs show good correlation between the direction and intensity of prevailing currents and the location and shape of the features in the bay. This indicates that although Galway Bay was shaped glacially through the passage of the British-Irish Ice Sheet across the bay and ensuing glacial and marine sediment deposition, many of the mapped seafloor landforms are modern and current-induced. ARTICLE HISTORY

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Sediment transport, aqueous bedform stability and morphodynamics under unidirectional current: a brief overview

Cited by 27 publications

References 76 publications

Sediment undulations on the Llobregat prodelta: Signs of early slope instability or sedimentary bedforms?

Sediment undulations on the Llobregat prodelta: Signs of early slope instability or sedimentary bedforms?

Channel flow competence and sediment transport in upland streams in southeast Australia

Geomorphology and substrate of Galway Bay, Western Ireland

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