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

Autor(es):Mostrar menos -

Cisneros, Julia ^[1] ; Best, Jim ^{[2, 1, 3, 4, 5]} ; van Dijk, Thaienne ^{[1, 6]} ; de Almeida, Renato Paes ^{[7, 8]} ; Amsler, Mario ^[9] ; Boldt, Justin ^[10] ; Freitas, Bernardo ^[11] ; Galeazzi, Cristiano ^[7] ; Huizinga, Richard ^[12] ; Ianniruberto, Marco ^[13] ; Ma, Hongbo ^[14] ; Nittrouer, Jeffrey A. ^[14] ; Oberg, Kevin ^[15] ; Orfeo, Oscar ^[16] ; Parsons, Dan ^[17] ; Szupiany, Ricardo ^[18] ; Wang, Ping ^[19] ; Zhang, Yuanfeng ^[19]

Afiliação do(s) autor(es):Mostrar menos -

^[1] Univ Illinois, Dept Geol, Urbana, IL 61801 - USA

^[2] Univ Illinois, Dept Mech Sci & Engn, Urbana, IL 61801 - USA

^[3] Univ Illinois, Dept Geog, Urbana, IL 61801 - USA

^[4] Univ Illinois, Dept GIS, Urbana, IL 61801 - USA

^[5] Univ Illinois, Ven Te Chow Hydrosyst Lab, Urbana, IL 61801 - USA

^[6] Deltares, Dept Appl Geol & Geophys, Utrecht - Netherlands

^[7] Univ Sao Paulo, Inst Geociencias, Sao Paulo - Brazil

^[8] Univ Sao Paulo, Inst Energia & Ambiente, Sao Paulo - Brazil

^[9] Natl Sci & Tech Res Council, Inst Nacl Limnol, Santa Fe - Argentina

^[10] US Geol Survey, Ohio Kentucky Indiana Water Sci Ctr, Louisville, KY - USA

^[11] Univ Estadual Campinas, Fac Tecnol, Limeira - Brazil

^[12] US Geol Survey, Cent Midwest Water Sci Ctr, Rolla, MO - USA

^[13] Univ Brasilia, Inst Geociencias, Brasilia, DF - Brazil

^[14] Rice Univ, Dept Earth Environm & Planetary Sci, Houston, TX - USA

^[15] US Geol Survey, Cent MidWest Water Sci Ctr, Urbana, IL - USA

^[16] Natl Sci & Tech Res Council, Ctr Ecol Aplicada, Corrientes - Argentina

^[17] Univ Hull, Energy & Environm Inst, Kingston Upon Hull, N Humberside - England

^[18] Univ Nacl Litoral, Fac Engn & Water Sci, Int Ctr Large Rivers Res, Santa Fe - Argentina

^[19] Yellow River Inst Hydraul Res, Zhengzhou - Peoples R China

• Tipo de documento: Artigo Científico
• Fonte: NATURE GEOSCIENCE; JAN 2020.
• Citações Web of Science: 0

Resumo

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. (AU)

• Processo FAPESP: 17/06874-3 - Dinâmica fluvial e depósitos sedimentares no Rio Amazonas: providenciando ferramentas para decifrar a evolução paleogeográfica da Amazônia e depósitos de grandes rios no registro rochoso
• Beneficiário: Cristiano Padalino Galeazzi
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 14/16739-8 - Desenvolvimento de modelos de fácies para grandes rios: processos e produtos em barras ativas na Amazônia Brasileira e implicações para as reconstruções paleogeográficas do Neógeno na Amazônia e do Mesozóico gondwanico no NE-Brasil e E-Austrália
• Beneficiário: Renato Paes de Almeida
• Modalidade de apoio: Auxílio à Pesquisa - Regular