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

Abstract

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.

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Fig. 1: PDF plots for the mean and maximum dune lee-side angles in each river and all rivers combined.
Fig. 2: Maximum slope of the dune lee-side angle.
Fig. 3: Relation between flow depth and dune height.
Fig. 4: Hotspot graph of the potential for flow separation.

Data availability

Data plotted herein will be available through https://databank.illinois.edu/datasets/IDB-7525764. Bathymetric data of all rivers are available through the respective survey team that acquired the data. Requests should be made to the authors referenced in the Supplementary Information.

Code availability

The code for BAMBI is available from the corresponding author on request.

References

  1. 1.

    Best, J. L. The fluid dynamics of river dunes: a review and some future research directions. J. Geophys. Res. Earth Surf. 110, JF000218 (2005).

  2. 2.

    Allen, J. R. L. The diffusion of grains in the lee of ripples, dunes, and sand deltas. J. Sediment. Res. 38, 621–633 (1968).

  3. 3.

    Bennett, S. J. & Best, J. L. Mean flow and turbulence structure over fixed, two-dimensional dunes: implications for sediment transport and bedform stability. Sedimentology 42, 491–513 (1995).

  4. 4.

    McLean, S. R., Nelson, J. M. & Wolfe, S. R. Turbulence structure over two-dimensional bed forms: implications for sediment transport. J. Geophys. Res. Oceans 99, 12729–12747 (1994).

  5. 5.

    Parsons, D. R. et al. Morphology and flow fields of three-dimensional dunes, Rio Paraná, Argentina: results from simultaneous multibeam echo sounding and acoustic Doppler current profiling. J. Geophys. Res. Earth Surf. 110, F04S03 (2005).

  6. 6.

    Jordan, D. W. & Pryor, W. A. Hierarchical levels of heterogeneity in a Mississippi River meander belt and application to reservoir systems: Geologic note (1). AAPG Bull. 76, 1601–1624 (1992).

  7. 7.

    Leclair, S. F. & Bridge, J. S. Quantitative interpretation of sedimentary structures formed by river dunes. J. Sediment. Res. 71, 713–716 (2001).

  8. 8.

    Amsler, M. L., Blettler, M. C. & Ezcurra de Drago, I. Influence of hydraulic conditions over dunes on the distribution of the benthic macroinvertebrates in a large sand bed river. Water Resour. Res. 45, W06426 (2009).

  9. 9.

    Allan, J. D. & Castillo, M. M. Stream Ecology: Structure and Function of Running Waters 2nd edn 33–56 (Springer, 2007).

  10. 10.

    Hickin, E. J. The development of meanders in natural river-channels. Am. J. Sci. 274, 414–442 (1974).

  11. 11.

    Southard, J. B. & Boguchwal, L. A. Bed configuration in steady unidirectional water flows. Part 2: synthesis of flume data. J. Sediment. Res. 60, 658–679 (1990).

  12. 12.

    Van Den Berg, J. I. & Van Gelder, A. in Alluvial Sedimentation Special Publication 17 (eds Marzo, M. & Puigdefábregas, C.) 11–21 (International Association of Sedimentologists, 1993).

  13. 13.

    Yalin, M. S. Geometrical properties of sand wave. J. Hydraul. Div. 90, 105–119 (1964).

  14. 14.

    Guy, H. P., Simons, D. B. & Richardson, E. V. Summary of Alluvial Channel Data from Flume Experiments, 1956-61 Geological Survey Professional Paper 462-I (United States Department of the Interior, Geological Survey, 1966).

  15. 15.

    Roden, J. E. The Sedimentology and Dynamics of Mega-dunes, Jamuna River, Bangladesh. PhD thesis, Univ. Leeds (1998).

  16. 16.

    Kostaschuk, R. & Villard, P. Flow and sediment transport over large subaqueous dunes: Fraser River, Canada. Sedimentology 43, 849–863 (1996).

  17. 17.

    Kostaschuk, R. A field study of turbulence and sediment dynamics over subaqueous dunes with flow separation. Sedimentology 47, 519–531 (2000).

  18. 18.

    Best, J. L. & Kostaschuk, R. An experimental study of turbulent flow over a low-angle dune. J. Geophys. Res. Oceans https://doi.org/10.1029/2000JC000294 (2002).

  19. 19.

    Shugar, D. H. et al. On the relationship between flow and suspended sediment transport over the crest of a sand dune, Río Paraná, Argentina. Sedimentology 57, 252–272 (2010).

  20. 20.

    Kostaschuk, R. A. & Venditti, J. G. Why do large, deep rivers have low-angle dune beds? Geology 47, 919–922 (2019).

  21. 21.

    Allen, J. R. L. & Collinson, J. D. The superimposition and classification of dunes formed by unidirectional aqueous flows. Sediment. Geol. 12, 169–178 (1974).

  22. 22.

    Allen, J. R. L. Polymodal dune assemblages: an interpretation in terms of dune creation-destruction in periodic flows. Sediment. Geol. 20, 17–28 (1978).

  23. 23.

    Reesink, A. J. & Bridge, J. Influence of bedform superimposition and flow unsteadiness on the formation of cross strata in dunes and unit bars-Part 2, further experiments. Sediment. Geol. 222, 274–300 (2009).

  24. 24.

    Galeazzi, C. P. et al. The significance of superimposed dunes in the Amazon River: implications for how large rivers are identified in the rock record. Sedimentology 65, 2388–2403 (2018).

  25. 25.

    Lefebvre, A., Paarlberg, A. J. & Winter, C. Characterising natural bedform morphology and its influence on flow. Geo-Mar. Lett. 36, 379–393 (2016).

  26. 26.

    Motamedi, A., Afzalimehr, H., Gallichand, J. & Abadi, E. F. N. Lee angle effects in near bed turbulence: an experimental study on low and sharp angle dunes. Int. J. Hydraul. Eng. 1, 68–74 (2012).

  27. 27.

    Motamedi., A., Afzalimehr, H., Zenz, G. & Galoie, M. in Advances in Hydroinformatics (eds Gourbesville, P. et al.) 525–533 (Springer, 2014).

  28. 28.

    Lefebvre, A. & Winter, C. Predicting bed form roughness: the influence of lee side angle. Geo-Mar. Lett. 36, 121–133 (2016).

  29. 29.

    Kwoll, E., Venditti, J. G., Bradley, R. W. & Winter, C. Flow structure and resistance over subaquaeous high-and low-angle dunes. J. Geophys. Res. Earth Surf. 121, 545–564 (2016).

  30. 30.

    Ashley, G. M. Classification of large-scale subaqueous bedforms: a new look at an old problem. J. Sediment. Res. 60, 160–172 (1990).

  31. 31.

    Paola, C. & Borgman, L. Reconstructing random topography from preserved stratification. Sedimentology 38, 553–565 (1991).

  32. 32.

    Bridge, J. S. & Tye, R. S. Interpreting the dimensions of ancient fluvial channel bars, channels, and channel belts from wireline-logs and cores. AAPG Bull. 84, 1205–1228 (2000).

  33. 33.

    Bradley, R. W. & Venditti, J. G. Reevaluating dune scaling relations. Earth-Sci. Revi. 165, 356–376 (2017).

  34. 34.

    Bradley, R. W. & Venditti, J. G. Transport scaling of dune dimensions in shallow flows. J. Geophys. Res. Earth Surf. 124, 526–547 (2019).

  35. 35.

    Van der Mark, C. F., Blom, A. & Hulscher, S. J. Quantification of variability in bedform geometry. J. Geophys. Res. Earth Surf. 113, F03020 (2008).

  36. 36.

    Fielding, C. R. in Large Rivers: Geomorphology and Management (ed. Gupta, A) 97–113 (John Wiley & Sons, 2008).

  37. 37.

    Costello, W. R. & Southard, J. B. Flume experiments on lower-flow-regime bed forms in coarse sand. J. Sediment. Res. 51, 849–864 (1981).

  38. 38.

    Ditchfield, R. & Best, J. Discussion of “Development of Bed Features" by Arved J. Raudkivi and Hans-H. Witte (September, 1990, Vol. 116, No. 9). J. Hydraul. Eng. 118, 647–650 (1992).

  39. 39.

    Best, J. in Advances in Fluvial Dynamics and Stratigraphy (eds Carling, P. A. & Dawson, M. R.) 67–125 (John Wiley & Sons, 1996).

  40. 40.

    Amsler, M. & Schreider, M. Aspectos hidráulicos de la superposición de formas de fondo en el Río Paraná (Argentina). In Proc. XV Congreso Latinoamericano de Hidráulica, X Seminario Nacional de Hidráulica e Hidrología 3, 8–12 (IAHR, 1992).

  41. 41.

    de Almeida, R. P. et al. Large barchanoid dunes in the Amazon River and the rock record: implications for interpreting large river systems. Earth and Planetary Science Letters 454, 92–102 (2016).

  42. 42.

    Hendershot, M. L. et al. Response of low-angle dunes to variable flow. Sedimentology 63, 743–760 (2016).

  43. 43.

    Baas, J. H. & Best, J. L. The dynamics of turbulent, transitional and laminar clay-laden flow over a fixed current ripple. Sedimentology 55, 635–666 (2008).

  44. 44.

    Baas, J. H., Best, J. L. & Peakall, J. Predicting bedforms and primary current stratification in cohesive mixtures of mud and sand. J. Geol. Soc. 173, 12–45 (2016).

  45. 45.

    Amsler, M. L. & Schreider, M. I. in River Sedimentation: Theory and Applications (eds Jayewardena, A. et al.) 615–620 (1999).

  46. 46.

    Ma, H. et al. The exceptional sediment load of fine-grained dispersal systems: example of the Yellow River, China. Sci. Adv. 3, e1603114 (2017).

  47. 47.

    Bridge, J. S. & Best, J. L. Flow, sediment transport and bedform dynamics over the transition from dunes to upper-stage plane beds: implications for the formation of planar laminae. Sedimentology 35, 753–763 (1988).

  48. 48.

    Saunderson, H. C. & Lockett, F. P. in Modern and Ancient Fluvial Systems (eds Collinson, J. & Lewin, J.) 49–58 (Wiley, 1983).

  49. 49.

    Naqshband, S., Ribberink, J. S. & Hulscher, S. J. Using both free surface effect and sediment transport mode parameters in defining the morphology of river dunes and their evolution to upper stage plane beds. J. Hydraul. Eng. 140, 06014010 (2014).

  50. 50.

    Martin, R. L. & Jerolmack, D. J. Origin of hysteresis in bed form response to unsteady flows. Water Resour. Res. 49, 1314–1333 (2013).

  51. 51.

    Reesink, A. J. et al. The adaptation of dunes to changes in river flow. Earth-Sci. Rev. 185, 1065–1087 (2018).

  52. 52.

    Wright, S. & Parker, G. Flow Resistance and suspended load in sand-bed rivers: simplified stratification model. J. Hydraul. Eng. 130, 796–805 (2004).

  53. 53.

    Latrubesse, E. M. Patterns of anabranching channels: the ultimate end-member adjustment of mega rivers. Geomorphology 101, 130–145 (2008).

  54. 54.

    Getirana, A. C. & Paiva, R. C. Mapping large-scale river flow hydraulics in the Amazon Basin. Water Resour. Res. 49, 2437–2445 (2013).

  55. 55.

    Ten Brinke, W. B., Wilbers, A. W. & Wesseling, C. Dune growth, decay and migration rates during a large-magnitude flood at a sand and mixed sand–gravel bed in the Dutch Rhine River System in Fluvial Sedimentology VI (eds Smith, N. & Rogers, J.) 15–32 (Wiley Blackwell, 1999).

  56. 56.

    Wilbers, A. W. & Ten Brinke, W. B. The response of subaqueous dunes to floods in sand and gravel bed reaches of the Dutch Rhine. Sedimentology 50, 1013–1034 (2003).

  57. 57.

    Julien, P. Y., Klaassen, G. J., Ten Brinke, W. B. & Wilbers, A. W. Case study: bed resistance of Rhine River during 1998 flood. J. Hydraul. Eng. 128, 1042–1050 (2002).

  58. 58.

    Frings, R. M. & Kleinhans, M. G. Complex variations in sediment transport at three large river bifurcations during discharge waves in the river Rhine. Sedimentology 55, 1145–1171 (2008).

  59. 59.

    Paarlberg, A. J., Dohmen-Janssen, C., Hulscher, S., Termes, P. & Schielen, R. Modelling the effect of time-dependent river dune evolution on bed roughness and stage. Earth Surf. Proc. Land. 35, 1854–1866 (2010).

  60. 60.

    Warmink, J. J. Dune dynamics and roughness under gradually varying flood waves, comparing flume and field observations. Adv. Geosci. 39, 115–121 (2014).

  61. 61.

    Einstein, H. A. The Bed-Load Function for Sediment Transportation in Open Channel Flows Technical Bulletin No. 1026 (US Department of Agriculture, 1950).

  62. 62.

    van Rijn, L. C. Sediment transport. Part III: bed forms and alluvial roughness. J. Hydraul. Eng. 110, 1733–1754 (1984).

  63. 63.

    Ogink, H. Hydraulic Roughness of Single and Compound Bed Forms (Delft Hydraulics, 1989).

  64. 64.

    Paarlberg, A. J., Dohmen-Janssen, C., Hulscher, S. & Termes, P. A parameterization of flow separation over subaqueous dunes. Water Resour. Res. 43, W12417 (2007).

  65. 65.

    Paarlberg, A. J., Dohmen-Janssen, C., Hulscher, S. & Termes, P. Modeling river dune evolution using a parameterization of flow separation. J. Geophys. Res. Earth Surf. 114, F01014 (2009).

  66. 66.

    Kornman, B. The Effect of Changes in the Lee Shape of Dunes on the Flow Field, Turbulence, and Hydraulic Roughness Report R 95-1 (University of Utrecht, 1995).

  67. 67.

    User Manual Delft3D-Flow (Deltares, 2011).

  68. 68.

    Schreider, M. I. & Amsler, M. L. Bedforms steepness in alluvial streams. J. Hydraul. Res. 30, 725–743 (1992).

  69. 69.

    Wignall, P. B. & Best, J. L. The Western Irish Namurian Basin reassessed. Basin Res. 12, 59–78 (2000).

  70. 70.

    Sambrook Smith, G. H., Best, J. L., Orfeo, O., Vardy, M. E. & Zinger, J. A. Decimeter-scale in situ mapping of modern cross-bedded dune deposits using parametric echo sounding: A new method for linking river processes and their deposits. Geophys. Res. Lett. 40, 3883–3887 (2013).

  71. 71.

    Leeder, M. R. Fluviatile fining-upwards cycles and the magnitude of palaeochannels. Geol. Mag. 110, 265–276 (1973).

  72. 72.

    Sambrook Smith, G. H., Ashworth, P. J., Best, J. L., Woodward, J. & Simpson, C. J. The sedimentology and alluvial architecture of the sandy braided South Saskatchewan River, Canada. Sedimentology 53, 413–434 (2006).

  73. 73.

    Best, J. & Bridge, J. The morphology and dynamics of low-amplitude bedwaves upon upper stage plane beds and the preservation of planar laminae. Sedimentology 39, 737–752 (1992).

  74. 74.

    van Dijk, T. A., Lindenbergh, R. C. & Egberts, P. J. Separating bathymetric data representing multiscale rhythmic bed forms: a geostatistical and spectral method compared. J. Geophys. Res. Earth Surf. 113, F04017 (2008).

  75. 75.

    Gutierrez, R. R., Abad, J. D., Parsons, D. R. & Best, J. L. Discrimination of bed form scales using robust spline filters and wavelet transforms: methods and application to synthetic signals and bed forms of the Río Paraná, Argentina. J. Geophys. Res. Earth Surf. 118, 1400–1418 (2013).

  76. 76.

    Burrough, P. A., McDonnell, R. A. & Lloyd, C. D. Principles of Geographical Information Systems 3rd edn (Oxford Univ. Press, 2015).

  77. 77.

    Dietsch, B. J., Densmore, B. K. & Wilson, R. C. Hydrographic Survey of Chaktomuk, the Confluence of the Mekong, Tonlé Sap, and Bassac Rivers Near Pnom Penh, Cambodia, 2012 Technical Report No. 2014-5227 (United States Geological Survey, 2014).

  78. 78.

    Nittrouer, J. A., Allison, M. A. & Campanella, R. Bedform transport rates for the lowermost Mississippi River. J. Geophys. Res. Earth Surf. 113, JF000795 (2008).

  79. 79.

    Huizinga, R. J. Results of Repeat Bathymetric and Velocimetric Surveys at the Amelia Earhart Bridge on US Highway 59 over the Missouri River at Atchison, Kansas, 2009–2013 Technical Report No. 2013-5177 (US Geological Survey, 2013).

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Acknowledgements

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.

Author information

J.C. and J.B. conceived the study and identified the potential datasets to be analysed. J.C. developed the BAMBI code from initial conceptual ideas on utilizing slope and aspect maps by J.B., and conducted the analysis and data plotting. All authors provided bathymetric data. J.C., J.B. and T.v.D. wrote the manuscript, which was then reviewed and edited by all authors.

Correspondence to Julia Cisneros or Jim Best.

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Peer review information Primary Handling Editors: Xujia Jiang, Melissa Plail.

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Extended data

Extended Data Fig. 1

Flow chart illustrating the BAMBI methodology.

Extended Data Fig. 2 River conditions and dune morphology statistics.

Statistics of flow discharge, Froude number (Fr, Eq. 1a), grain size, H/Y, dune height (H), dune wavelength (\(\it \lambda\)), H/\(\it \lambda\), superimposed dune height (Hs), Hs/\(\it {\lambda }_{{\rm{s}}}\), and Hs/Hmean. xEstimated mean discharge during survey. *Discharge range for multiple surveys. +N total is not same for superimposed dunes and large dunes. Mean values are found from first calculating the value of each individual dune then averaging.

Extended Data Fig. 3 Dune schematic showing the morphologic parameters measured in BAMBI.

Values measured are dune height (H), wavelength (\(\lambda\)), mean lee-side angle, maximum lee-side slope, height of the maximum lee-side slope (h), and flow depth (Y).

Extended Data Fig. 4 Lee-side angle statistics.

Statistics for mean and maximum lee-side angles in each river and for all rivers compiled. +N total is not same for superimposed dunes and large dunes.

Extended Data Fig. 5 Distribution of mean and maximum dune lee-side angles in the Huang He (Yellow) River.

Lee-side measurements were acquired using the BAMBI method from single echosounder lines.

Extended Data Fig. 6

Distribution of mean dune lee-side angles in the Jamuna (Brahmaputra) River (data from15).

Extended Data Fig. 7 Distribution of dune aspect ratio (\(\it \lambda\)/H) for all rivers and dunes with different lee-side angles.

Statistics given for the mean and standard deviation (std dev.) for all rivers and dunes with lee-side angles \(<1{0}^{\circ }\), \(10-2{4}^{\circ }\) and \(>2{4}^{\circ }\), which are related to zones of no flow separation, developing flow separation, and permanent, fully developed flow separation. N represents the number of data points that fall within each category.

Extended Data Fig. 8

Flow depth vs mean lee-side angle for all rivers.

Extended Data Fig. 9 Dune height vs lee-side angle.

a) mean and b) maximum lee-side angle for all rivers, and c) mean and d) maximum lee-side angle for the: i) Amazon, ii) Mekong, iii) Paraná, iv) Mississippi, v) Missouri, and vi) Waal rivers. As examples, grey arrows in part c), panels i) and iv) for the Amazon and Mississippi rivers, highlight the trends of increasing minimum mean angle (solid line) and decreasing maximum mean angle (dashed line) for dunes.

Supplementary information

Supplementary Information

Supplementary Fig.1.

Source data

Source Data Extended Data Fig. 1

Excel table of Extended Data Fig. 4

Source Data Extended Data Fig. 2

Excel table of Extended Data Fig. 2

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Cisneros, J., Best, J., van Dijk, T. et al. Dunes in the world’s big rivers are characterized by low-angle lee-side slopes and a complex shape. Nat. Geosci. 13, 156–162 (2020). https://doi.org/10.1038/s41561-019-0511-7

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