Autogenic Formation of Bimodal Grain Size Distributions in Rivers and Its Contribution to Gravel‐Sand Transitions
Abstract Riverbeds often fine downstream, with a gravel‐bedded reach, a relatively abrupt gravel‐sand transition (GST), and a sand‐bedded reach. Underlying this behavior, bed grain size distributions are often bimodal, with a relative paucity (gap) around the range 1–5 mm. There is no general morpho...
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| Format: | Article |
| Language: | English |
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Wiley
2024-09-01
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| Series: | Geophysical Research Letters |
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| Online Access: | https://doi.org/10.1029/2024GL109109 |
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| author | Chenge An Gary Parker Jeremy G. Venditti Michael P. Lamb Marwan A. Hassan Hiroshi Miwa Xudong Fu |
| author_facet | Chenge An Gary Parker Jeremy G. Venditti Michael P. Lamb Marwan A. Hassan Hiroshi Miwa Xudong Fu |
| author_sort | Chenge An |
| collection | DOAJ |
| description | Abstract Riverbeds often fine downstream, with a gravel‐bedded reach, a relatively abrupt gravel‐sand transition (GST), and a sand‐bedded reach. Underlying this behavior, bed grain size distributions are often bimodal, with a relative paucity (gap) around the range 1–5 mm. There is no general morphodynamic model capable of producing the grain size gap and gravel‐sand transition autogenically from a unimodal sediment supply. Here we use a one‐dimensional morphodynamic model including size‐specific bedload and suspended load transport, to show that bimodality readily evolves autogenically even under unimodal sediment feed. A GST forms when we include a floodplain width that abruptly increases at some point. Upstream of the transition, non‐gap gravel ceases to move and gap sediment is preferentially transported. At the transition, non‐gap sand rapidly deposits from suspension, enhancing gap sediment mobility and diluting its presence on the bed. |
| format | Article |
| id | doaj-art-0f2fc175a40b41dfb739cdcd98d1301f |
| institution | OA Journals |
| issn | 0094-8276 1944-8007 |
| language | English |
| publishDate | 2024-09-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geophysical Research Letters |
| spelling | doaj-art-0f2fc175a40b41dfb739cdcd98d1301f2025-08-20T02:10:39ZengWileyGeophysical Research Letters0094-82761944-80072024-09-015117n/an/a10.1029/2024GL109109Autogenic Formation of Bimodal Grain Size Distributions in Rivers and Its Contribution to Gravel‐Sand TransitionsChenge An0Gary Parker1Jeremy G. Venditti2Michael P. Lamb3Marwan A. Hassan4Hiroshi Miwa5Xudong Fu6State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin China Institute of Water Resources and Hydropower Research Beijing ChinaDepartment of Civil and Environmental Engineering Department of Earth Science and Environmental Change University of Illinois at Urbana‐Champaign Urbana IL USASchool of Environmental Science Simon Fraser University Burnaby BC CanadaDivision of Geological and Planetary Sciences California Institute of Technology Pasadena CA USADepartment of Geography The University of British Columbia Vancouver BC CanadaDepartment of Social Systems and Civil Engineering Tottori University Tottori JapanDepartment of Hydraulic Engineering State Key Laboratory of Hydroscience and Engineering Tsinghua University Beijing ChinaAbstract Riverbeds often fine downstream, with a gravel‐bedded reach, a relatively abrupt gravel‐sand transition (GST), and a sand‐bedded reach. Underlying this behavior, bed grain size distributions are often bimodal, with a relative paucity (gap) around the range 1–5 mm. There is no general morphodynamic model capable of producing the grain size gap and gravel‐sand transition autogenically from a unimodal sediment supply. Here we use a one‐dimensional morphodynamic model including size‐specific bedload and suspended load transport, to show that bimodality readily evolves autogenically even under unimodal sediment feed. A GST forms when we include a floodplain width that abruptly increases at some point. Upstream of the transition, non‐gap gravel ceases to move and gap sediment is preferentially transported. At the transition, non‐gap sand rapidly deposits from suspension, enhancing gap sediment mobility and diluting its presence on the bed.https://doi.org/10.1029/2024GL109109bimodalitygravel‐sand transitionbedloadsuspended loadgrain size distribution |
| spellingShingle | Chenge An Gary Parker Jeremy G. Venditti Michael P. Lamb Marwan A. Hassan Hiroshi Miwa Xudong Fu Autogenic Formation of Bimodal Grain Size Distributions in Rivers and Its Contribution to Gravel‐Sand Transitions Geophysical Research Letters bimodality gravel‐sand transition bedload suspended load grain size distribution |
| title | Autogenic Formation of Bimodal Grain Size Distributions in Rivers and Its Contribution to Gravel‐Sand Transitions |
| title_full | Autogenic Formation of Bimodal Grain Size Distributions in Rivers and Its Contribution to Gravel‐Sand Transitions |
| title_fullStr | Autogenic Formation of Bimodal Grain Size Distributions in Rivers and Its Contribution to Gravel‐Sand Transitions |
| title_full_unstemmed | Autogenic Formation of Bimodal Grain Size Distributions in Rivers and Its Contribution to Gravel‐Sand Transitions |
| title_short | Autogenic Formation of Bimodal Grain Size Distributions in Rivers and Its Contribution to Gravel‐Sand Transitions |
| title_sort | autogenic formation of bimodal grain size distributions in rivers and its contribution to gravel sand transitions |
| topic | bimodality gravel‐sand transition bedload suspended load grain size distribution |
| url | https://doi.org/10.1029/2024GL109109 |
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