Opposite hysteresis of sand and gravel transport upstream and downstream of a bifurcation during a flood in the River Rhine, the Netherlands
Bibliographic record
Abstract
Abstract At river bifurcations water and sediment is divided among the downstream branches. Prediction of the sediment transport rate and division thereof at bifurcations is of utmost importance for understanding the evolution of the bifurcates for short-term management purposes and for long-term fluvial plain development. However, measured sediment transports in rivers rarely show a uniquely determined relation with hydrodynamic parameters. Commonly a hysteresis is observed of transport rate as a function of discharge or shear stress which cannot be explained with the standard sediment transport predictor approach. The aim of this paper is to investigate the causes of hysteresis at a bifurcation of the lower Rhine river, a meandering river with stable banks, large dunes during flood, and poorly sorted bed sediment. The hydrodynamics and bed sediment transport were measured in detail during a discharge wave with a recurrence interval larger than 10 years. Surprisingly, the hysteresis in bedload against discharge was in the opposite direction upstream and downstream of the bifurcation. The upstream clockwise hysteresis is caused by the lagging development of dunes during the flood. The counter-clockwise hysteresis downstream of the bifurcation is caused by a combination of processes in addition to dune lagging, namely 1) formation of a scour zone upstream of the bifurcation, causing a migrating fine sediment wave, and 2) vertical bed sorting of the bed sediment by dunes with avalanching lee-sides, together leading to surface-sediment fining and increased transport during and after the flood. These findings lead to challenges for future morphological models, particularly for bifurcations, which will have to deal with varying discharge, sediment sorting in the channel bed, lagging dunes and related hydraulic roughness.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".