Bed form genesis from bed defects under unidirectional, oscillatory, and combined flows

2014 ◽  
Vol 119 (12) ◽  
pp. 2635-2652 ◽  
Author(s):  
M. M. Perillo ◽  
E. W. Prokocki ◽  
J. L. Best ◽  
M. H. García
Keyword(s):  
Bed Form ◽  
Geology ◽  
2020 ◽  
Vol 48 (12) ◽  
pp. 1144-1148
Author(s):  
Chenliang Wu ◽  
Jeffrey A. Nittrouer ◽  
Travis Swanson ◽  
Hongbo Ma ◽  
Eric Barefoot ◽  
...  

Abstract Dune-scale cross-beds are a fundamental building block of fluvial-deltaic stratigraphy and have been recognized on Earth and other terrestrial planets. The architecture of these stratal elements reflects bed-form dynamics that are dependent on river hydrodynamic conditions, and previous work has documented a multitude of scaling relationships to describe the morphodynamic interactions between dunes and fluid flow. However, these relationships are predicated on normal flow conditions for river systems and thus may be unsuitable for application in fluvial-deltaic settings that are impacted by nonuniform flow. The ways in which dune dimensions vary systematically due to the influence of reach-averaged, nonuniform flow, and how such changes may be encoded in dune cross-strata, have not been investigated. Herein, we explored the influence of backwater flow on dune geometry in a large modern fluvial channel and its implications for interpretation of systematic variability in dune cross-strata in outcrop-scale stratigraphy. This was accomplished by analyzing high-resolution channel-bed topography data for the lowermost 410 km of the Mississippi River, which revealed that dune size increases to a maximum before decreasing toward the river outlet. This spatial variability coincides with enhanced channel-bed aggradation and decreasing dune celerity, which arise due to backwater hydrodynamics. An analytical model of bed-form stratification, identifying spatial variability of cross-set thickness, indicates a prominent downstream decrease over the backwater region. These findings can be used to inform studies of ancient fluvial-deltaic settings, by bolstering assessments of proximity to the marine terminus and associated spatially varying paleohydraulics.


1982 ◽  
Vol 7 (1) ◽  
pp. 17-28 ◽  
Author(s):  
S. A. Schumm ◽  
D. W. Bean ◽  
M. D. Harvey
Keyword(s):  

1971 ◽  
Vol 97 (2) ◽  
pp. 358-359
Author(s):  
Maurice J. Crickmore
Keyword(s):  

2014 ◽  
Vol 2014 ◽  
pp. 1-12
Author(s):  
Chin-Ping Lin ◽  
Yu-Min Wang ◽  
Samkele S. Tfwala ◽  
Ching-Nuo Chen

Taiwan, because of its location, is a flood prone region and is characterised by typhoons which brings about two-thirds to three quarters of the annual rainfall amount. Consequently, enormous flows result in rivers and entrain some fractions of the grains that constitute the riverbed. Hence, the purpose of the study is to quantify the impacts of these enormous flows on the distribution of grain size in riverbeds. The characteristics of riverbed material prior to and after the typhoon season are compared in Shi-Wen River located at southern Taiwan. These include grain size variation, bimodality, and roughness coefficient. A decrease (65%) and increase (50%) in geometric mean size of grains were observed for subsurface and surface bed material, respectively. Geometric standard deviation decreased in all sites after typhoon. Subsurface material was bimodal prior to typhoons and polymodal after. For surface material, modal class is in the gravel class, while after typhoons it shifts towards cobble class. The reduction in geometric mean resulted to a decrease in roughness coefficient by up to 30%. Finally, the relationship of Shields and Froude numbers are studied and a change in the bed form to antidunes and transition form is observed, respectively.


Geology ◽  
1997 ◽  
Vol 25 (9) ◽  
pp. 771 ◽  
Author(s):  
B. T. Werner ◽  
G. Kocurek
Keyword(s):  

2021 ◽  
Author(s):  
Ronald R. Gutierrez ◽  
Frank E. Escusa ◽  
Alice Lefebvre ◽  
Carlo Gualtieri ◽  
Francisco Nunez-Gonzalez ◽  
...  

<p>Open and data-driven paradigms have allowed to answer fundamental scientific questions in different disciplines such as astronomy, ecology and fluid mechanics, among others. Recently, the need to collaboratively build a large, engineered and freely accessible bed form database has been highlighted as a necessary step to adopt these paradigms in bed form dynamics research.</p><p>Most large database architectures have followed the principles of relational databases model solutions (RDBMS). Recently, non-relational (NoSQL) architectures (e.g., key-value store, graph databases, document-oriented, etc.) have been proposed to improve the capabilities and flexibility of RDBMS. Both RDBMS and NoSQL architectures require designing an engineered metadata structure to define the data taxonomy and structure, which are subsequently used to develop a metadata language for data querying. Past research suggests that the development of a metadata language needs a collaborative and iterative approach.</p><p>Defining the data taxonomy and structure for bed form data may be challenging because: [1] there is not a standardized protocol for conducting field and laboratory measurements; [2] it is expected that existing bed form data have a wide spectrum of data characteristics (e.g. length, format, resolution, structured or non-structured, etc.); and [3] bedforms are studied by scientists and engineers from different disciplines (e.g., geologists, ecologists, civil and water engineers, etc.).</p><p>In recent years, several data repositories have been built to manage large datasets related to the Earth System. One of these repositories is the Earth Science Information Partners, which has proposed standards to promote and improve the preservation, availability and overall quality of Earth System related data. These standards map the roles of participants (e.g., creators, intermediaries and end users) and delivers protocols to ensure proper data distribution and quality control.</p><p>This contribution presents the first iteration of a metadata language for subaqueous bed form data, named BedformsML0, which adopts the standards of the Earth Science Information Partners. BedformsML0 may serve as a prototype to describe bed form observations from field and laboratory measurements, model outputs, technical reports, scientific papers, post processed data, etc. Biogeoenvironmental observations associated to bed form dynamics (e.g., hydrodynamics, turbulence, river and coastal morphology, biota density, habitat metrics, sediment transport, sediment properties, land use dynamics, etc.) may also be represented in BedformsML0. It could subsequently be improved in future iterations via the collaboration of professionals from different Earth science fields to also describe subaerial, and extraterrestrial bed form data. Likewise, BedformsML0 can be used as machine search query selection for massive data processing and visualization of bed form observations. </p>


1971 ◽  
Vol 97 (2) ◽  
pp. 353-358
Author(s):  
Li-San Hwang ◽  
David Divoky
Keyword(s):  

1973 ◽  
Vol 99 (1) ◽  
pp. 121-137
Author(s):  
Christopher John Pratt
Keyword(s):  
Bed Form ◽  

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