Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Long-term Trend Evaluation of Meandering Channel Planform at Mean Annual Subcritical Flow to Support Riparian Management

Version 1 : Received: 8 February 2023 / Approved: 9 February 2023 / Online: 9 February 2023 (03:58:56 CET)

A peer-reviewed article of this Preprint also exists.

Song, X., Xu, H., & Bai, Y. (2023). Long-term Trend Evaluation of Meandering Channel Planform at Mean Annual Subcritical Flow to Support Riparian Management. International Journal of Sediment Research. Song, X., Xu, H., & Bai, Y. (2023). Long-term Trend Evaluation of Meandering Channel Planform at Mean Annual Subcritical Flow to Support Riparian Management. International Journal of Sediment Research.

Abstract

This study numerically evaluated the long-term and stable trends of meandering channel planform at different mean annual subcritical flows based on a depth-averaged linearized meander evolution model. The calculation cases included an idealized sine-generated meander with moderate max-deflection angle and a typical natural meander - Jiyun River (in China). Within the increase of the selection of the mean annual width-depth ratio in a certain scope, the results showed some specific phase characteristics of channel centerline evolution: (1) the meander straightening trend became weaker in phase 1 (B/H ≤ 16.5) and gradually turned into the meander developing trend in phase 2 (B/H ≤ 27) with the overall immunity to flow magnitude; (2) the symmetric development form along the transverse direction perpendicular to the flow average direction was broken starting from the downstream tail in phase 3 (B/H ≤ 28.9), meantime accompanied by the highlight of flow effects when the mean annual B/H exceeded 28; (3) in phase 4 (B/H ≤ 29.5), there occurred obvious incipience and jump process of the channel sensitivity responding to flow when the selected B/H crossed 29.3, which were very similar to the transition process from the laminar flow to turbulent flow. Besides, the initial sinuosity and curvature-ratio indicator could contribute much to the channel evolutionary state, as demonstrated in the comparison between natural Jiyun River case and the correspondingly idealized sine-generated meander case with the same level of mean annual B/H. This research provides innovation spaces for deeper meander mechanism exploration and effective riparian management.

Keywords

long-term trend; meander planform; subcritical flow; width-depth ratio; riparian management

Subject

Environmental and Earth Sciences, Environmental Science

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