Experimental Investigation of Physical Leaky Barrier Design Implications on Juvenile Rainbow Trout (Oncorhynchus mykiss) Movement

Stephanie Müller,Joanne Cable,Catherine A M E Wilson,Pablo Ouro

doi:10.1029/2021wr030111

Stephanie Müller, Joanne Cable + Show 2 more

Open Access

https://doi.org/10.1029/2021wr030111

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Abstract

AbstractRivers have been subject to the construction of numerous small‐scale anthropogenic structures, causing the alteration and fragmentation of habitats. Despite their impact on fish habitat selection, migration, and swimming performance, more hydraulic structures are being added to riverine systems. These mainly have the purpose of harnessing renewable energy or mitigating the impact of flooding, as in the case of leaky barriers that are widely used for natural flood management. By providing a sustainable and cost‐effective supplement to traditional hard engineering flood risk management methods, these channel‐spanning wooden barriers are constructed using sustainable, local materials, intended to slow down surface water and groundwater flow, reduce flood peaks, and attenuate the flow reaching downstream communities. Despite their increasing popularity, little is known about the design implications on fish movement or hydrodynamics. Using scaled laboratory flume experiments we investigate how the physical design of four leaky barriers varying in porosity, length, provision of overhead cover, and color, impact on fish movement and spatial usage, and the channel hydrodynamics. Our fish behavioral analysis reveals that juvenile rainbow trout (Oncorhynchus mykiss) movement reduces with barrier presence. Upstream passage increases with barrier color but not cover, for shorter rather than longer leaky barriers, and for a non‐porous barrier compared to its porous counterpart. Barrier‐specific flow alterations appear to play a secondary role compared to barrier color. Our study showed that physical barrier design and leaky barrier presence alter fish movement, and therefore care needs to be taken during the design of such natural flood management structures.

Highlights

Rivers are subject to the wide-scale construction of anthropogenic structures, ranging from large hydropower and reservoir dams to low-to-zero head structures such as weirs, culverts, sluices, water intakes and outtakes, and riverine turbines
Our study showed that physical barrier design and leaky barrier presence alter fish movement, and care needs to be taken during the design of such natural flood management structures
Leaky barriers were installed in the flume under the same flowrate and downstream control conditions (Table 1), which resulted in a significant change in the channel hydrodynamics and water surface profile due to their presence obstructing the flow (Figures 5b–5i)

Summary

Introduction

Rivers are subject to the wide-scale construction of anthropogenic structures, ranging from large hydropower and reservoir dams to low-to-zero head structures such as weirs, culverts, sluices, water intakes and outtakes, and riverine turbines. The resulting river fragmentation poses a threat to biodiversity and in particular to fish movement (Jones et al, 2019; Reid et al, 2019) by presenting physical, chemical, thermal, and hydraulic barriers (Silva et al, 2018). This can result in movement delay (Silva et al, 2018) and increased energetic swimming costs (Enders et al, 2003). Great effort has been undertaken in retrofitting (e.g., weirs [Amaral et al, 2019], culverts [Goodrich et al, 2018]) and partially removing existing barriers (e.g., Sullivan et al, 2019), and developing fishways (Silva et al, 2018) to restore longitudinal river connectivity by enabling upstream and downstream movement of target species

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