Dunes in the world's big rivers are characterized by low-angle lee-side slopes and a complex shape
Julia Cisneros, Jim Best, Thaiënne van Dijk, Renato Paes de Almeida, Mario Amsler, Justin Boldt, Bernardo Freitas, Cristiano Galeazzi, Richard Huizinga, Marco Ianniruberto, Hongbo Ma, Jeffrey A. Nittrouer, Kevin Oberg, Oscar Orfeo, Dan Parsons, Ricardo Szupiany, Ping Wang, Yuanfeng Zhang
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Agradecimentos: J.C. is supported by a National Science Foundation Graduate Research Fellowship (NSF GRF). This material is based on work supported by the National Science Foundation Graduate Research Fellowship under grant no. DGE-1746047. J.C. is also supported by the Department of Geology,...
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Agradecimentos: J.C. is supported by a National Science Foundation Graduate Research Fellowship (NSF GRF). This material is based on work supported by the National Science Foundation Graduate Research Fellowship under grant no. DGE-1746047. J.C. is also supported by the Department of Geology, University of Illinois, and the Jack and Richard C. Threet chair to J.B. The Huang He (Yellow) River single-beam echosounder data acquisition was supported by the National Natural Science Foundation of China (grant no. 51379087), the Department of Geology, University of Illinois, and the Jack and Richard C. Threet chair to J.B. We also thank the São Paulo Research Foundation (FAPESP) for Research Grant nos. 2014/16739-8 and 2017/06874-3, supporting the acquisition of the Amazon River Multibeam Echo Sounder data. J.B. would like to acknowledge many discussions with R. Kostaschuk, who first highlighted the importance of low-angle alluvial dunes. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation
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Abstract: Dunes in the world's big rivers are dominated by lee-side slopes with angles of less than 10 degrees, according to a bedform analysis of high-resolution bathymetric datasets. Dunes form critical agents of bedload transport in all of the world's big rivers, and constitute appreciable...
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Abstract: Dunes in the world's big rivers are dominated by lee-side slopes with angles of less than 10 degrees, according to a bedform analysis of high-resolution bathymetric datasets. Dunes form critical agents of bedload transport in all of the world's big rivers, and constitute appreciable sources of bed roughness and flow resistance. Dunes also generate stratification that is the most common depositional feature of ancient riverine sediments. However, current models of dune dynamics and stratification are conditioned by bedform geometries observed in small rivers and laboratory experiments. For these dunes, the downstream lee-side is often assumed to be simple in shape and sloping at the angle of repose. Here we show, using a unique compilation of high-resolution bathymetry from a range of large rivers, that dunes are instead characterized predominantly by low-angle lee-side slopes (<10 degrees), complex lee-side shapes with the steepest portion near the base of the lee-side slope and a height that is often only 10% of the local flow depth. This radically different shape of river dunes demands that such geometries are incorporated into predictions of flow resistance, water levels and flood risk and calls for rethinking of dune scaling relationships when reconstructing palaeoflow depths and a fundamental reappraisal of the character, and origin, of low-angle cross-stratification within interpretations of ancient alluvial sediments
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FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP
2014/16739-8; 2017/06874-3
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Dunes in the world's big rivers are characterized by low-angle lee-side slopes and a complex shape
Julia Cisneros, Jim Best, Thaiënne van Dijk, Renato Paes de Almeida, Mario Amsler, Justin Boldt, Bernardo Freitas, Cristiano Galeazzi, Richard Huizinga, Marco Ianniruberto, Hongbo Ma, Jeffrey A. Nittrouer, Kevin Oberg, Oscar Orfeo, Dan Parsons, Ricardo Szupiany, Ping Wang, Yuanfeng Zhang
Dunes in the world's big rivers are characterized by low-angle lee-side slopes and a complex shape
Julia Cisneros, Jim Best, Thaiënne van Dijk, Renato Paes de Almeida, Mario Amsler, Justin Boldt, Bernardo Freitas, Cristiano Galeazzi, Richard Huizinga, Marco Ianniruberto, Hongbo Ma, Jeffrey A. Nittrouer, Kevin Oberg, Oscar Orfeo, Dan Parsons, Ricardo Szupiany, Ping Wang, Yuanfeng Zhang
Fontes
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Nature geoscience v. 13, n. 1, p. 156-162, Jan. 2020 |