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Article

Assessing Riverbed Surface Destabilization Risk Downstream Isolated Vegetation Elements

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School of Engineering, University of Glasgow, Glasgow G12 8LT, UK
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Department of Hydroscience and Engineering, Faculty of Civil Engineering, University of Zagreb, HR-10000 Zagreb, Croatia
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School of Civil Engineering, National Technical University of Athens, 15773 Athens, Greece
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Research and Innovation Department, INNOVATEQUE, 15561 Athens, Greece
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Civil Engineering Faculty, Division of Hydraulics, School of Engineering, Istanbul Technical University, Istanbul 34469, Turkey
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Institute of Geophysics, Polish Academy of Sciences, 01-452 Warsaw, Poland
*
Authors to whom correspondence should be addressed.
Academic Editor: Achim A. Beylich
Water 2022, 14(18), 2880; https://doi.org/10.3390/w14182880
Received: 27 July 2022 / Revised: 27 August 2022 / Accepted: 2 September 2022 / Published: 15 September 2022
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. View Full-Text
Keywords: instream vegetation; entrainment rate; coarse sediment; flow turbulence; impulse; sensors; instrumentation instream vegetation; entrainment rate; coarse sediment; flow turbulence; impulse; sensors; instrumentation
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MDPI and ACS Style

Xu, Y.; Valyrakis, M.; Gilja, G.; Michalis, P.; Yagci, O.; Przyborowski, Ł. Assessing Riverbed Surface Destabilization Risk Downstream Isolated Vegetation Elements. Water 2022, 14, 2880. https://doi.org/10.3390/w14182880

AMA Style

Xu Y, Valyrakis M, Gilja G, Michalis P, Yagci O, Przyborowski Ł. Assessing Riverbed Surface Destabilization Risk Downstream Isolated Vegetation Elements. Water. 2022; 14(18):2880. https://doi.org/10.3390/w14182880

Chicago/Turabian Style

Xu, Yi, Manousos Valyrakis, Gordon Gilja, Panagiotis Michalis, Oral Yagci, and Łukasz Przyborowski. 2022. "Assessing Riverbed Surface Destabilization Risk Downstream Isolated Vegetation Elements" Water 14, no. 18: 2880. https://doi.org/10.3390/w14182880

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