Stream-barb installations for narrow channel bends — a laboratory study
Bibliographic record
Abstract
Phase 1 of an ongoing laboratory study of a novel form of stream-bank protection structure is described. "Barbs" are dike-like stone structures designed to protect the (usually unstable) outside-bank regions of channel bends. These low-profile structures point upstream into the flow and typically extend to about 1/4-way across the channel. By disrupting near-bank velocity gradients they promote sediment deposition along the eroding outside-bank region. Their presence also modifies the "helicoidal"-type flow pattern of the bend such that secondary currents, which would otherwise attack the outside-bank, are redirected towards the center of the channel. This novel form of bank protection structure is currently undergoing field tests on selected bends on a number of shallow "wide" streams in Illinois, USA. While initial results are encouraging, additional studies are necessary to develop design criteria for their wider application. In phase 1 of this study, the effectiveness of different arrangements of barb groups, in both 90° and 135° moveable-bed bend sections of a hydraulically "narrow" rectangular channel, are investigated. For each hydraulic condition considered, the channel-bed scour profiles generated by the different barb groups are compared to corresponding "reference" profiles generated in the absence of barbs. Judging the effectiveness of the different barb groups in promoting long-term stability of the outside-bank region is based on two criteria: (i) percent reduction achieved in scouring in the vicinity of the outside-bank and (ii) degree to which the channel thalweg (deepest portion) is moved from the outside-bank region towards the center of the channel.Key words: barb, channel bends, local scouring, bank erosion, bank protection, secondary currents.
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How this classification was reachedexpand
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 | 0.000 | 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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".