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Modeling Tidal Circulation and Stratification in an Intertidal Estuary with
an Unstructured Coastal Ocean Model and High Resolution Lidar Data
Zhaoqing Yang1 and Tarang Khangaonkar
Battelle Marine Sciences Laboratory
1100 Dexter Avenue North, Suite 400, Seattle, WA 98109, USA
Abstract
Tidal circulation and fresh water plume dynamics in shallow water
estuarine systems with large intertidal zones are complex. Wetting and drying
processing in intertidal zone and relatively large changes of water depth in tidal
channels over a tidal cycle results in strong asymmetries in tidal currents and
stratification during flood and ebb tidal phases. The Skagit River estuary is one
of several complex intertidal estuaries in the Puget Sound, Washington. It
consists of a large intertidal zone with multiple tidal channels. The Skagit River
is the largest river to flow into the Puget Sound estuarine system. It discharges
about 39% of total sediment and more than 20% of freshwater into Puget Sound.
To simulate the tidal circulation and stratification accurately in Skagit River
estuary, a numerical model with unstructured frame work and wetting-drying
capability is required. In addition, high resolution bathymetry data is also
required to correctly represent the network of tidal channels with a relatively
small scale. In this paper, a three-dimensional hydrodynamic model was
developed for the Skagit River Estuary using an unstructured finite volume
coastal ocean model FVCOM and high resolution lidar data in the study area.
The hydrodynamic model was calibrated using observed tidal elevation, velocity,
and salinity data over a spring and neap tidal cycle. Wetting and drying process
in the intertidal zone and strong variations of tidal currents and stratification in
subtidal channels were predicted successfully in the model with agreement to the
field observation.
Model results demonstrated that the dynamics of tidal
circulation and salinity stratification in the intertidal zone and subtidal channels in
the Skagit River estuary can be simulated well with a combination of an
unstructured coastal ocean model and high resolution bathymetry lidar data.
Key words: Unstructured Model, Intertidal Zone, Tidal Circulation, Stratification
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Corresponding author: email: zhaoqing.yang@pnl.gov; phone: 206-528-3057
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