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Momentum and energy predict the Backwater rise generated by a large wood jam

Follett, E. ORCID:, Schalko, I. and Nepf, H. 2020. Momentum and energy predict the Backwater rise generated by a large wood jam. Geophysical Research Letters 47 (17) , e2020GL089346. 10.1029/2020GL089346

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Wood reintroduction is now considered an important aspect of stream restoration, due to ecohydraulic benefits associated with wood presence. Channel‐spanning wood jams create an upstream backwater, increasing flow heterogeneity, sediment deposition, and ecological productivity, but also flood risk. Backwater rise prediction is necessary to evaluate flood hazards in hydraulic models, improve design of engineered logjam projects, and compare jam effects across river systems. We present experimental results demonstrating that a jam can be modeled as a porous obstruction generating momentum loss proportional to the number, size, and packing density of the logs and the jam length. Energy and momentumconstraints are combined to predict backwater rise from unit discharge and a dimensionless structural parameter. This novel approach allows description of preexisting jams with a common metric. The model was used to demonstrate how backwater length, pool size, and upstream sediment deposition depend on jam structure and channel slope.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Engineering
Publisher: American Geophysical Union (AGU)
ISSN: 0094-8276
Date of First Compliant Deposit: 14 August 2020
Date of Acceptance: 10 August 2020
Last Modified: 11 May 2023 16:09

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