Flow and sediment suspension events over low‐angle dunes: Fraser Estuary, Canada
Why this work is in the frame
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Bibliographic record
Abstract
Abstract The morphodynamics of large sand‐bedded rivers and estuaries are ultimately controlled by the way bed material is moved and the development of large, subaqueous sand dunes that control hydraulic flow resistance. It is widely thought that the primary mechanism for moving sandy bed material in these channels is large‐scale coherent flow structures that cause suspension events whose properties vary with flow, especially in tidally influenced environments. Here, we examine mean flow and sediment suspension events over low‐angle dunes (lee face angle <30°) in the unsteady flow of the Fraser Estuary, Canada. At high tide, flow nearly ceased and a salt wedge entered the channel, forcing salt water under the downstream‐moving fresh water. The salt wedge persisted in the channel until late in the falling tide, causing stratification in the water column and instabilities along the saline‐fresh water interface. At low tide, mean velocities peaked and forced the saline water out of the channel. Flow over the low‐angle dunes displayed topographically induced patterns previously observed over high‐angle dunes, but permanent flow separation was not observed. Large‐scale sediment suspension events dominated sediment flux during low tide and became larger scale, yet less frequent, as the tide began to rise. The suspension events appeared to form over the lower stoss of the dunes and grew up over the bed forms and, less commonly, emerged downstream of the crest. Suspension events move ~69% of the total sediment in the flow above low‐angle dunes when they are present.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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 it