ABSTRACT: Flow Structure and Bed Topography in Submarine Meandering Channels

AAPG Bulletin ◽  
2001 ◽  
Vol 85 ◽  
Author(s):  
Jasim Imran1, Ahmed Kassem1
Keyword(s):  
Flow Structure ◽  
Bed Topography ◽  
Meandering Channels

scholarly journals Topics in fluvial and lagoon morphodynamics

2002 ◽  
Author(s):  
Luca Solari
Keyword(s):  
Flow Field ◽  
Bedload Transport ◽  
Observational Evidence ◽  
Field Pattern ◽  
Tidal Channels ◽  
New Model ◽  
Bed Topography ◽  
Meandering Channels ◽  
Present Book ◽  
Transverse Slope

The present book covers topics both on fluvial and lagoon morphodynamics. The first part is dedicated to tidal environments. Topics include an overview of main morphological features and mechanisms of estuaries and tidal channels and a model devoted to investigate flow field pattern and bed topography in tidal meandering channels and a comparison with recent observational evidence of meanders within different tidal environments. The general failure of Bagnold hypothesis when applied to equilibrium bedload transport at even relatively modest transverse slope is demonstrated. A new model is then proposed based on an empirical entrainment formulation of bed grains.

scholarly journals Experiments on Longitudinal and Transverse Bedload Transport in Sine-Generated Meandering Channels

2021 ◽  
Vol 11 (14) ◽  
pp. 6560
Author(s):  
Li He ◽  
Dong Chen ◽  
Donatella Termini ◽  
Shiyan Zhang ◽  
Zhenhui Zhu
Keyword(s):  
Longitudinal Direction ◽  
Bedload Transport ◽  
Bed Topography ◽  
Bed Deformation ◽  
Meandering Channels ◽  
Curved Channels ◽  
Initial Location ◽  
Moving Direction ◽  
Point Bars ◽  
Gain Loss

Bedload grains in consecutive meandering bends either move longitudinally or across the channel centerline. This study traces and quantifies the grains’ movement in two laboratorial sine-generated channels, i.e., one with deflection angle θ0 = 30° and the other 110°. The grains originally paved along the channels are uniform in size with D = 1 mm and are dyed in various colors, according to their initial location. The experiments recorded the changes in the flow patterns, bed deformation, and the gain-loss distribution of the colored grains in the pool-bar complexes. We observed the formation of two types of erosion zones during the process of the bed deformation, i.e., Zone 1 in the foreside of the point bars and Zone 2 near the concave bank downstream of the bend apexes. Most grains eroded from Zone 1 are observed moving longitudinally as opposed to crossing the channel centerline. Contrastingly, the dominant moving direction of the grains eroded from Zone 2 changes from the longitudinal direction to the transversal one as the bed topography evolves. Besides, most building material of the point bars comes from the upstream bends, although low- and highly curved channels behave differently.

Erosion of bedrock by subglacial meltwater, Georgian Bay, Ontario: a regional view

1991 ◽  
Vol 28 (4) ◽  
pp. 623-642 ◽  
Author(s):  
P. S. G. Kor ◽  
J. Shaw ◽  
D. R. Sharpe
Keyword(s):  
Flow Structure ◽  
Regional Scale ◽  
Wide Area ◽  
Glacial Lake ◽  
Flow Structures ◽  
Hudson Bay ◽  
Georgian Bay ◽  
Bed Topography ◽  
Coherent Flow Structures ◽  
Subglacial Meltwater

A spectacular series of sculpted erosional forms (s-forms) is mapped and described from a 70 km wide area along the shore of Georgian Bay, Ontario, which, except for a scattered boulder lag, has been swept clean of sediment. A great variety of sculpted forms is described and illustrated and grouped into three classes: transverse, longitudinal, and nondirectional forms. Transverse forms comprise transverse troughs, muschelbrüche, sichelwannen, and comma forms; longitudinal forms comprise spindle flutes, cavettos, and furrows; and nondirectional forms consist of undulating surfaces and potholes. Transverse forms are preferentially located on stoss slopes, and longitudinal forms on lee slopes of rock rises. Undulating, nondirectional forms are found on distal slopes, and potholes at major breaks in slope. This correlation of form and bed topography suggests that relief exerts considerable control on both form and location. Form geometry is also inferred to be related to coherent flow structures and their interaction with the bed. Flow scale, vorticity, separation, bifurcation, strength, and direction are inferred from erosional-mark properties. In some cases, erosional forms appear to have caused the flow structure by which they were perpetuated. Sculpted forms occur at different scales, and the inferred flow structures are thought to have operated over the same scale range.Attributes of the forms, boulder lags, and inferred flow structures clearly reflect erosion by powerful, turbulent, subglacial meltwater flows. The erosional forms are observed over an area 70 km wide, which, taken together with a strongly uniform paleoflow direction, indicates regional-scale flow. The Georgian Bay floods were comparable in discharge (~107 m3/s) with floods from glacial Lake Missoula, Livingstone Lake drumlins, and Sable Island tunnel valleys. The most likely site for the storage of meltwater that drained catastrophically to form the erosional-mark field was the lowland stretching north from the Abitibi Highlands to Hudson Bay.

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