Journal Article

River Meander Development by Bar‐Push and Bank‐Pull During Cyclic Hydrographs in a Field‐Scale Experimental Channel

Trudel, Mélanie, Biron, Pascale M, Sklar, Leonard S, Mahmoud, Basem M. M, Lacey, Jay

2026

Overview

Gravel‐bed rivers widen and narrow as bar‐push and bank‐pull wax and wane through individual floods, yet over decades the channel often holds near constant width, evidence of coupling between inner‐bank deposition and outer‐bank erosion. Because large, event‐scale data sets are scarce and most field rivers have mixed grain‐size beds, the physics of this coupling remains uncertain. Here we use a unique Outdoor Experimental River Facility (OERF) with sediment recirculation to investigate this coupling in 50 m‐long, 3 m‐wide sine‐generated gravel‐bed channel using four identical seven‐stage flood hydrographs (129‐hr total duration). In an unvegetated experimental gravel‐bed channel with erodible banks (50% gravel; median size of 16 mm), twenty‐nine drone photogrammetry surveys (i.e., 2mm$2\\ \\mathrm{m}\\mathrm{m}$Digital Elevation Models) and bedload samples were collected to determine a novel thalweg‐centered volumetric framework and analysis that partitions every survey into inner‐bank and outer‐bank contributions. Flood peaks, though only 3% of the experiment duration, produced 83% of the 52% increase in planform area relative to the initial condition: centroid migration reached 1.3 m (27% of width), with the widening varying from one bend to the other. At peaks, bank‐pull dominated 50% of events and bar‐push 40%, whereas during rising and falling limbs symmetric widening prevailed (41%) with bar‐push still active (31%). Local context modulated these stage effects: under identical forcing, one bend damped toward a medium‐stability balance that approached a steady but non‐zero bar‐push/bank‐pull imbalance, a mid‐reach bend reached high stability with near‐balanced inner and outer bank volumetric changes, and an outlet‐proximal bend diverged into low‐stability widening. We conclude that in gravel channels the bar‐push/bank‐pull is both stage‐dependent and bend‐specific; short peaks set the morphodynamic trajectory, but sub‐bankfull limbs are responsible for most of the in‐channel geomorphic work.

• Publisher: John Wiley & Sons, Inc
• Subject: Bank erosion / Bed load / Centroids / Coupling / Digital Elevation Models / Flood hydrographs / Floods / Geomorphology / Gravel / Hydrographs / Outlets / Photogrammetry / Physics / River channels / River meanders / Rivers / Sediment transport / Soil erosion / Stability / Surveys / Thalweg / Widening