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Flow and wake characteristics associated with large wood to inform river restoration

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author SchalkoIsabella, NepfHeidi, WohlEllen,
Project Hydrodynamic and morphological processes associated with wood accumulation patches
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Original article (peer-reviewed)

Journal Scientific Reports
Volume (Issue) 11(8644 )
Page(s) 1 - 12
Title of proceedings Scientific Reports
DOI 10.1038/s41598-021-87892-7

Open Access

URL https://www.nature.com/articles/s41598-021-87892-7
Type of Open Access Publisher (Gold Open Access)

Abstract

Wood is an integral part of a river ecosystem and the number of restoration projects using log placements is increasing. Physical model tests were used to explore how the wood position and submergence level (discharge) affect wake structure, and hence the resulting habitat. We observed a von-Kármán vortex street (VS) for emergent logs placed at the channel center, while no VS formed for submerged logs, because the flow entering the wake from above the log (sweeping flow) inhibited VS formation. As a result, emergent logs placed at the channel center resulted in ten times higher turbulent kinetic energy compared to submerged logs. In addition, both spatial variation in time-mean velocity and turbulence level increased with increasing log length and decreasing submergence level. Submerged logs and logs placed at the channel side created a greater velocity deficit and a longer recirculation zone, both of which can increase the residence time in the wake and deposition of organic matter and nutrients. The results demonstrate that variation in log size and degree of submergence can be used as a tool to vary habitat suitability for different fish preferences. To maximize habitat diversity in rivers, we suggest a diverse large wood placement.
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