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A Nonlinear state shift: Morphodynamic reconfiguration under progressive vegetation uprooting on alternate bars
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DOI：10.1007/s42241-026-0049-2.png)
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Abstract
En 中文
Vegetation fundamentally regulates river-bar morphology. However, the morphodynamic response of bars to the progressive removal of vegetation remains insufficiently characterized. Flume experiments with two steady flows were conducted using a two-stage uprooting protocol: Stage 1 trimmed about 30% from the leading edge of an apex patch; Stage 2 cleared the remainder. Bed evolution was analyzed using depth-normalized relief, areal aggradation-degradation fractions, lateral mass-balance metrics, and thalweg-based wavelength. Partial removal of 30% of the vegetation (Stage 1) produced a sharp morphodynamic shift: The area experiencing net aggradation increased from roughly 20%–25% to 56%–77% of the bar surface. This indicates a transition from scour-dominated to deposition-dominated adjustment and a reorganization of the bar-wake system. In contrast, complete removal (Stage 2) stabilized the deposition-dominated bar configuration established by Stage 1, with deposition remaining dominant and the flow wake lengthening and reattaching farther downstream. At higher discharge (Q2 = 0.003 m3/s), bar wavelength expanded by ∼10%–59%, reflecting longer wakes and reduced roughness, while the lower discharge (Q1 = 0.002 5 m3/s) mainly deepened local relief without major re-spacing. Morphodynamically, Stage 1 drives the reconfiguration, converting a forced, asymmetric deflector bar into a diffusively depositional form. Subsequently, Stage 2 acts as the stabilizer, allowing the reach to relax toward a free-bar template governed by intrinsic flow-sediment dynamics. Practically, these findings highlight that partial vegetation loss can induce instability, initially producing a localized scour hotspot at the patch’s new leading edge, even as it drives the bar into an overall deposition-dominated state. In contrast, complete clearing tends to redistribute sediment more evenly and stabilize bar spacing, offering direct guidance for river restoration and vegetation-management design.
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