Impact of leaky barriers and hydrokinetic turbines on channel hydrodynamics and fish movement

Muller, Stephanie 2021. Impact of leaky barriers and hydrokinetic turbines on channel hydrodynamics and fish movement. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

Rivers have been subject to the construction of numerous small and large-scale an-thropogenic structures, causing the alteration and fragmentation of aquatic habitats. Despite the tremendous impact of these structures on fish movement and the aquatic environment, more obstructions are added to riverine systems, mainly for flood mitigation or harnessing renewable energy. As little is known about the ecological impacts of these structures, further research is required to minimise the risk of these obstructions presenting a barrier to fish movement. By the means of two case studies, this thesis aims to quantify the effects of two emerging in-stream obstructions, namely leaky barriers used for natural flood management (Chapter 2) and vertical axis hydrokinetic turbines (Chapter 3). Using scaled laboratory experiments, changes in channel hydrodynamics and fish movement were determined for each of the two barriers. Leaky barrier hydrodynamics were characterised by flow diversion upstream of all structures, the formation of a modified wall jet underneath the barrier, and a structure-dependent upper wake. Juvenile Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) movement was not prevented by barrier presence but resulted in decreased upstream passage and proportion of time spent upstream. The wake of a vertical axis turbine was asymmetric about the turbine’s centreline and shifted towards the upstroke side. Due to this wake asymmetry, the individual wakes of twin-turbines either moved alongside each other, converged, or diverged depending on the turbine rotational direction. Juvenile rainbow trout avoided the near turbine region and remained in the free-stream area under unconfined conditions. Small groups of fish were more explorative compared to individuals. This thesis expands our current knowledge on these two emerging barriers, supporting their delivery as environmental-friendly, anthropogenic in-stream obstructions while ensuring flood mitigation, sustainable energy generation, and habitat connectivity.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Engineering
Uncontrolled Keywords:	Ecohydraulics, Fish behaviour , Renewable energy , Hydrokinetic vertical axis turbine , Leaky barrier , Natural flood management
Date of First Compliant Deposit:	19 July 2022
Last Modified:	19 Jul 2022 11:14
URI:	https://orca.cardiff.ac.uk/id/eprint/151365

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