Skip to main content
U.S. flag

An official website of the United States government

Dunes in the world's big rivers are characterized by low-angle lee-side slopes and a complex shape

January 20, 2020

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°), 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.

Publication Year 2020
Title Dunes in the world's big rivers are characterized by low-angle lee-side slopes and a complex shape
DOI 10.1038/s41561-019-0511-7
Authors Julia Cisneros, Jim L. Best, Thaienne van Dijk, Renato Paes de Almeida, Mario Amsler, Justin A. Boldt, Bernardo Freitas, Cristiano Galeazzi, Richard J. Huizinga, Marco Ianniruberto, Hongbo Ma, Jeff Nittrouer, Kevin Oberg, Oscar Orfeo, Daniel Parsons, Ricardo N. Szupiany, Ping Wang, Yuanfeng Zhang
Publication Type Article
Publication Subtype Journal Article
Series Title Nature Geoscience
Index ID 70208905
Record Source USGS Publications Warehouse
USGS Organization Missouri Water Science Center; WMA - Observing Systems Division