@article{53f63c54c09d4042a63a8b067e2d2283,
title = "Influence of Dunes on Channel-Scale Flow and Sediment Transport in a Sand Bed Braided River",
abstract = "Current understanding of the role that dunes play in controlling bar and channel-scale processes and river morphodynamics is incomplete. We present results from a combined numerical modeling and field monitoring study that isolates the impact of dunes on depth-averaged and near-bed flow structure, with implications for morphodynamic modeling. Numerical simulations were conducted using the three-dimensional computational fluid dynamics code OpenFOAM to quantify the time-averaged flow structure within a 400 m × 100 m channel using digital elevation models (DEMs) for which (i) dunes and bars were present within the model and (ii) only bar-scale topographic features were resolved (dunes were removed). Comparison of these two simulations shows that dunes enhance lateral flows and reduce velocities over bar tops by as much as 30%. Dunes influence the direction of modeled sediment transport at spatial scales larger than individual bedforms due to their effect on topographic steering of the near-bed flow structure. We show that dunes can amplify, dampen, or even reverse the deflection of sediment down lateral bar slopes, and this is closely associated with 3-D and obliquely orientated dunes. Sediment transport patterns calculated using theory implemented in depth-averaged morphodynamic models suggest that gravitational deflection of sediment is still controlled by bar-scale topography, even in the presence of dunes. However, improved parameterizations of flow and sediment transport in depth-averaged morphodynamic models are needed that account for the effects of both dune- and bar-scale morphology on near-bed flow and sediment transport.",
keywords = "2-D, 3-D, OpenFOAM, dune, river, sediment transport",
author = "Unsworth, {Christopher A.} and Nicholas, {Andrew P.} and Ashworth, {Philip J.} and Best, {James L.} and Lane, {Stuart N.} and Parsons, {Daniel R.} and {Sambrook Smith}, {Gregory H.} and Simpson, {Christopher J.} and Strick, {Robert J.P.}",
note = "Funding Information: P. J. A., A. P. N., D. R. P., and G. S. S. thank the UK Natural Environment Research Council (NERC) for grants NE/L00738X/1, NE/L005662/1, NE/L00450X/1, and NE/L005441/1 that funded this work. Vance and Janine Ylioja kindly gave us access to their land and boat launch, while Bill Vavra generously provided storage facilities and access to his land. Bob and Sandy Stephenson at the Irrigation Motel in Outlook provided invaluable assistance and logistical support. Image processing was performed using Pix4Dmapper software under an educational license (Pix4D SA, Switzerland). Simulations were run on the Exeter University High‐Performance Cluster ISCA. Professor Gavin Tabor and Dr. Recep Kahraman are thanked for their support with OpenFOAM. Dr. Tim Maddux is thanked for supplying his dune morphology and flow data for model validation. We thank the Editors, Dr. Alice Lefebvre, and two anonymous reviewers for very helpful and constructive reviews. Funding Information: P. J. A., A. P. N., D. R. P., and G. S. S. thank the UK Natural Environment Research Council (NERC) for grants NE/L00738X/1, NE/L005662/1, NE/L00450X/1, and NE/L005441/1 that funded this work. Vance and Janine Ylioja kindly gave us access to their land and boat launch, while Bill Vavra generously provided storage facilities and access to his land. Bob and Sandy Stephenson at the Irrigation Motel in Outlook provided invaluable assistance and logistical support. Image processing was performed using Pix4Dmapper software under an educational license (Pix4D SA, Switzerland). Simulations were run on the Exeter University High-Performance Cluster ISCA. Professor Gavin Tabor and Dr. Recep Kahraman are thanked for their support with OpenFOAM. Dr. Tim Maddux is thanked for supplying his dune morphology and flow data for model validation. We thank the Editors, Dr. Alice Lefebvre, and two anonymous reviewers for very helpful and constructive reviews. Publisher Copyright: {\textcopyright}2020. The Authors.",
year = "2020",
month = nov,
doi = "10.1029/2020JF005571",
language = "English (US)",
volume = "125",
journal = "Journal of Geophysical Research: Earth Surface",
issn = "2169-9003",
number = "11",
}