Morphological evolution and pattern identification of weakly tidal river channels: A case study of lower reaches of Yellow River

Abstract

[Objective] The morphological evolution mechanism of weakly tidal estuarine channels is complex. Clarifying its response to runoff and sediment dynamics is crucial for river channel regulation and flood control. [Methods] Systematic physical model experiments were conducted to observe the complete dynamic evolution process of meandering channels under different runoff and sediment conditions. Based on the mechanisms revealed by the tests, and combined with river resistance theory, parameters including channel slope, Froude number, and bed sediment size were introduced to construct characteristic morphological parameters. Historical hydrological cross-sectional data from the lower reaches of the Yellow River were classified using support vector machine(SVM), and quantitative criteria for river pattern identification were established. [Results] The experimental result indicated that river channel evolution exhibited a typical three-stage pattern: stable, slight change, and strong change. Runoff and sediment conditions dominated the evolution mode, where high flow triggered intense erosion and channel avulsion, while high sediment concentration led to deposition and channel widening. Based on this, quantitative thresholds for identifying wandering, braided, and meandering river patterns were established. Validation using recent river channel data confirmed the effectiveness of these criteria in identifying pattern transitions. For instance, the Sunkou-Aishan section was identified as transitioning towards a braided pattern, which was consistent with interpretations from remote sensing imagery. [Conclusion] Physical modeling is an effective approach for revealing river channel evolution mechanisms. The constructed morphological parameter model facilitates the transition from qualitative description to quantitative discrimination, offering theoretical guidance for river channel management.

Keywords

physical test / resistance pattern / river morphology / relative roughness / morphological parameters / support vector machine / sediment / remote sensing