Effect of Rigid Vegetation on Velocity Distribution and Bed Topography in a Meandering River with a Sloping Bank
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RESEARCH ARTICLE-CIVIL ENGINEERING
Effect of Rigid Vegetation on Velocity Distribution and Bed Topography in a Meandering River with a Sloping Bank Amirhossein Azarisamani1 · Alireza Keshavarzi1,2 · Hossein Hamidifar1 · Mahmoud Javan1 Received: 11 December 2019 / Accepted: 21 July 2020 © King Fahd University of Petroleum & Minerals 2020
Abstract In the present study, a physical model of a meandering river with the sloping bank was used to assess the effects of rigid vegetation on flow velocity distribution and bed scouring at the toe and bank slope of a meandering river. The experimental tests were carried out under non-vegetated condition as a reference and vegetated conditions with six different patterns. The results revealed that the flow velocity distribution and bed topography at each cross-section were considerably affected by vegetation density and planting patterns. For the vegetated condition, the longitudinal flow velocity component increased in the main channel, while it decreased in the bank zone when compared to the non-vegetated conditions. Additionally, in the presence of vegetation, the core of maximum velocity diverts toward the centerline of the flume, which reduces erosion risk. Furthermore, a comparison of the longitudinal velocity profiles under vegetated and non-vegetated conditions showed that the area occupied by the core of maximum velocity at the bend apex decreases up to 26%, notably for the conditions with double rows and hybrid patterns. The results of this study showed that the use of vegetation can be recommended to stabilize rivers’ bed and banks a green and cost-effective alternative to hard-engineering methods. Keywords Vegetation · Meandering channel · Bank slope · Flow velocity · Bed topography · Bank stability
1 Introduction The rivers are not always straight, and because of their intrinsic dynamics, frequently change from straight to meandering form. This deformation changes the pattern of flow and consequently scouring and deposition [1]. Meandering deformations has a significant impact on urban areas and farmlands located adjacent to the river. It is due to the erosion of the lands and consequently affect river water quality, as it is one of the most important sources of freshwater [2, 3]. Hence, an understanding of flow characteristics is quite vital for meandering river restoration and stabilization projects. There are a variety of methods to prevent or reduce riverbank erosion, among which the methods that restore the environment are also more relevant. In most recent studies * Hossein Hamidifar [email protected] 1
Water Engineering Department, Shiraz University, Shiraz, Iran
Centre for Infrastructure Engineering, School of Engineering, Western Sydney University, Penrith, Australia
2
(for example by [1, 4–11], it is highlighted that the selection of river restoration methods is crucial in river management plans. According to several studies (for example, [12–14]), one of the fundamental methods in river restoration projects is the use of natural trees
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