@article{3cebeb9ffdf44b8197e1ee3cf4e7abe3,
title = "Hydrodynamic modelling of tidal-fluvial flows in a large river estuary",
abstract = "The transition between riverine and estuarine environments is characterised by a change from unidirectional to bidirectional flows, in a region referred to herein as the Tidally-Influenced Fluvial Zone (TIFZ). In order to improve our understanding of the hydrodynamics and morphodynamics of this zone, we present a combined field and numerical modelling study of the Columbia River Estuary (CRE), USA, tidally-influenced fluvial zone. The CRE is large measuring 40 km in length and between 5 and 10 km wide. A shallow water model (Delft3D) was applied in both 2D and 3D configurations and model sensitivity to the key process parameterizations was investigated. Our results indicate that a 2D model constrained within the estuary can sufficiently reproduce depth-averaged flow within the TIFZ of a stratified estuary. Model results highlight the interactions between tidal-, fluvial- and topographic-forcing that result in depth dependent tidal rectification, and thus zones of residual sediment transport that: i) may be flood-directed along shallow channel margins and in the lee of bars, and simultaneously ii) is ebb-directed within deeper channel thalwegs. This condition is enhanced at lower discharges, but increased fluvial discharge reduces the number and size of regions with net flood-directed sediment transport and flow. These sediment transport patterns provide a mechanism to extend the bar/island topography downstream, and generate flood-directed, ebb-directed, and symmetrical bedforms, all within the same channel. Analysis of the model data reveals flood-directed sediment transport is due to both tidal variability and mean flow. These results highlight the need to include the mean flow component (M0) when considering the long-term morphodynamic evolution in a TIFZ.",
keywords = "Columbia river estuary, Model parameterisation, Residual flow, Sediment transport, Tidal constituent, Tidal-fluvial interactions",
author = "Sandbach, {S. D.} and Nicholas, {A. P.} and Ashworth, {P. J.} and Best, {J. L.} and Keevil, {C. E.} and Parsons, {D. R.} and Prokocki, {E. W.} and Simpson, {C. J.}",
note = "We are grateful to CMOP , USGS , NOAA , USACE , LCREP and PSLC (all fully referenced within the paper) for supplying bathymetric and hydrological data critical to the model application. Calculations for this study were performed using the University of Exeter Supercomputer. This work was supported by the Natural Environment Research Council (NERC) on a split grant award [grant numbers: NE/H007954/1 , NE/H006524/1 , NE/H007261/1 and NE/H00582X/1] . Fieldwork was made possible by access to the extensive facilities at the Clatsop Community College Marine and Environmental Research and Training Station ; we thank in particular Ant{\'o}nio Baptista, Michael Wilkin and Katie Rathmell for their help in servicing equipment, providing access to machine workshops, training in marine health and safety and provision of a Humber Class RIB. Rob Strick and Greg Sambrook Smith helped obtain some of the field data. Finally, we thank Pat Killion for his navigation skills on the Tansy Point and essential local expertise in the ever-changing conditions in the Columbia River Estuary. We are grateful to CMOP, USGS, NOAA, USACE, LCREP and PSLC (all fully referenced within the paper) for supplying bathymetric and hydrological data critical to the model application. Calculations for this study were performed using the University of Exeter Supercomputer. This work was supported by the Natural Environment Research Council (NERC) on a split grant award [grant numbers: NE/H007954/1, NE/H006524/1, NE/H007261/1 and NE/H00582X/1]. Fieldwork was made possible by access to the extensive facilities at the Clatsop Community College Marine and Environmental Research and Training Station; we thank in particular Ant{\'o}nio Baptista, Michael Wilkin and Katie Rathmell for their help in servicing equipment, providing access to machine workshops, training in marine health and safety and provision of a Humber Class RIB. Rob Strick and Greg Sambrook Smith helped obtain some of the field data. Finally, we thank Pat Killion for his navigation skills on the Tansy Point and essential local expertise in the ever-changing conditions in the Columbia River Estuary.",
year = "2018",
month = nov,
day = "15",
doi = "10.1016/j.ecss.2018.06.023",
language = "English (US)",
volume = "212",
pages = "176--188",
journal = "Estuarine, Coastal and Shelf Science",
issn = "0272-7714",
publisher = "Academic Press",
}