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Type: Artigo
Title: Dunes in the world's big rivers are characterized by low-angle lee-side slopes and a complex shape
Author: Cisneros, Julia
Best, Jim
Dijk, Thaienne van
Almeida, Renato Paes de
Amsler, Mario
Boldt, Justin
Freitas, Bernardo
Galeazzi, Cristiano
Huizinga, Richard
Ianniruberto, Marco
Ma, Hongbo
Nittrouer, Jeffrey A.
Oberg, Kevin
Orfeo, Oscar
Parsons, Dan
Szupiany, Ricardo
Wang, Ping
Zhang, Yuanfeng
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
Subject: Dunas
Country: Reino Unido
Editor: Nature Publishing Group
Rights: Fechado
Identifier DOI: 10.1038/s41561-019-0511-7
Date Issue: 2020
Appears in Collections:FT - Artigos e Outros Documentos

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