Assessing riverbed surface destabilization risk downstream isolated vegetation elements

Xu, Y., Valyrakis, M. , Gilja, G., Michalis, P., Yagci, O. and Przyborowski, Ł. (2022) Assessing riverbed surface destabilization risk downstream isolated vegetation elements. Water, 14(18), 2880. (doi: 10.3390/w14182880)

Abstract

A few decades ago, river erosion protective approaches were widely implemented, such as straightening the river course, enhancing riverbed/bank stability with layers of concrete or riprap, and increasing channel conveyance capacity (i.e., overwidening). However, recent research has established that such practices can be tremendously costly and adversely affect the rivers’ ecological health. To alleviate these effects, green river restoration has emerged as a sustainable and environmentally friendly approach that can reduce the negative impact of the riverbed and bank destabilization and flooding. One of the typical green restoration measures, especially for instream habitat improvement, is the establishment of instream vegetation, which leads to a more diversified flow regime, increasing habitat availability and serving as refugia for aquatic species. Within the perspective presented above, flow–vegetation interaction problems for several decades received significant attention. In these studies, rigid rods have commonly been used to simulate these vegetative roughness elements without directly assessing the riverbed destabilization potential. Here, an experimental study is carried out to investigate the effect of different instream vegetation porosity on the near-bed flow hydrodynamics and riverbed destabilization potential for a range of simulated vegetation species. Specifically, the flow field downstream, four distinct simulated vegetation elements is recorded using an acoustic Doppler velocimetry (ADV), assuming about the same solid volume fraction for the different vegetation elements. In addition, bed destabilization potential is assessed by recording with optical means (a He-Ne laser with a camera system) the entrainment rate of a 15 mm particle resting on the uniform bed surface and the number of impulses above a critical value. Results revealed that the number of impulses above a critical value at the normalized distance equal to two is a good indicator for cylinder and five for other vegetation to assess the riverbed destabilization potential. The experimental findings from this study have interesting geomorphological implications regarding the destabilization of the riverbed surface (removal of coarse particles induced by high magnitude turbulent impulses) and the successful establishment of seedlings downstream of instream vegetation.

• Item Type: Articles
• Additional Information: This work has been supported in part by the Royal Society (Research Grant RG2015 R1 68793/1), the Royal Society of Edinburg (Crucible Award), the Carnegie Trust for the Universities of Scotland (project 7066215), the Croatian Science Foundation under the project R3PEAT (UIP-2019-04- 4046) and the Polish Ministry of Education and Science.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Michalis, Dr Panagiotis and Valyrakis, Dr Manousos and Przyborowski, Mr Lukasz and Xu, Yi

Creator Roles

Xu, Y.: Methodology, Software, Validation, Formal analysis, Investigation, Resources, Data curation, Writing – original draft, Writing – review and editing, Visualization
Valyrakis, M.: Conceptualization, Methodology, Validation, Investigation, Resources, Data curation, Writing – review and editing, Visualization, Supervision, Project administration, Funding acquisition
Michalis, P.: Validation, Writing – review and editing
Przyborowski, Ł.: Methodology, Writing – review and editing

• Authors: Xu, Y., Valyrakis, M., Gilja, G., Michalis, P., Yagci, O., and Przyborowski, Ł.
• College/School: College of Science and Engineering > School of Engineering; College of Science and Engineering > School of Engineering > Infrastructure and Environment
• Journal Name: Water
• Publisher: MDPI
• ISSN: 2073-4441
• ISSN (Online): 2073-4441
• Published Online: 15 September 2022
• Copyright Holders: Copyright © 2022 The Authors
• First Published: First published in Water 14(18): 2880
• Publisher Policy: Reproduced under a Creative Commons License