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Water 2018, 10(2), 223; https://doi.org/10.3390/w10020223

Responses of Bed Morphology to Vegetation Growth and Flood Discharge at a Sharp River Bend

Hydraulic Research Laboratory, Hokkaido University, Hokkaido 060-8628, Japan
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Received: 14 November 2017 / Revised: 12 February 2018 / Accepted: 16 February 2018 / Published: 22 February 2018
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Abstract

In this study, we conducted simulations using a two-dimensional, depth-averaged river flow and river morphology model to investigate the effect of vegetation growth and degree of flow discharge on a shallow meandering channel. To consider the effects of these factors, it was assumed that vegetation growth stage is changed by water flow and bed erosion. The non-uniformity of the vegetation growth was induced by the non-uniform and unsteady profile of the water depth due to the irregular shape of the bed elevation and the unsteady flow model reliant on hydrographs to evaluate three types of peak discharges: moderate flow, annual average maximum flow, and extreme flow. To compare the effects of non-uniform growing vegetation, the change in channel patterns was quantified using the Active Braiding Index (ABI), which indicates the average number of channels with flowing water at a cross section and the Bed Relief Index (BRI), which quantifies the degree of irregularity of the cross-sectional shape. Two types of erosion were identified: local erosion (due to increased flow velocity near a vegetation area) and global erosion (due to the discharge approaching peak and the large depth of the channel). This paper demonstrated that the growth of vegetation increases both the ABI and BRI when the peak discharge is lower than the annual average discharge, whereas the growth of vegetation reduces the BRI when the peak discharge is extreme. However, under extreme discharge, the ABI decreases because global erosion is dominant. The conclusions from this study help to deepen the understanding of the interactions between curved river channels and vegetation. View Full-Text
Keywords: river bed morphology; sharp river bend; vegetation; 2-D shallow flow model; computational hydrodynamics river bed morphology; sharp river bend; vegetation; 2-D shallow flow model; computational hydrodynamics
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Kang, T.; Kimura, I.; Shimizu, Y. Responses of Bed Morphology to Vegetation Growth and Flood Discharge at a Sharp River Bend. Water 2018, 10, 223.

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