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Momentum and Energy Predict the Backwater Rise Generated by a Large Wood Jam

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Follett E., Schalko I., Nepf H.,
Project Hydrodynamic and morphological processes associated with wood accumulation patches
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Original article (peer-reviewed)

Journal Geophysical Research Letters
Volume (Issue) 47(17)
Page(s) 1 - 10
Title of proceedings Geophysical Research Letters
DOI 10.1029/2020gl089346

Open Access

URL http://doi.org/10.1029/2020GL089346
Type of Open Access Publisher (Gold Open Access)

Abstract

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 momentum constraints 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.
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