Hydrodynamic modelling in a micro-tidal salt wedge estuary: the Derwent River Estuary

Last week, MetOcean Solutions’ Senior Physical Oceanographer Remy Zyngfogel, presented his findings on hydrodynamic modelling in a micro-tidal salt wedge estuary at the Australasian Coasts & Ports 2019 conference in Hobart.


The research is a case study of the Derwent River Estuary, applying the Semi-implicit cross-scale Hydroscience Integrated System Model (SCHISM) to resolve the complex local-scale baroclinic hydrodynamics correctly. This modelling study enables a deeper understanding and description of the velocity structure within the Derwent estuary and will enable more current predictions to support vessel navigation within the estuary.


“The SCHISM model is an ideal tool for this type of cross-scale study,” says Remy. “The unstructured grids allow us to optimise model resolution to replicate salient hydrodynamic processes with approximately 300m resolution offshore, reduced to 20m in the nearshore and down to 2m under the Tasman Bridge.

Triangular elements of the model domain meshes.

Triangular elements of the model domain meshes.

“This approach allowed us to resolve key bathymetric features, including the individual bridge piles, which influence the hyper-local scale hydrodynamics, and provided greater resolution along the navigation channel.”

A nested modelling approach was applied, in which a high resolution SCHISM model domain was used to examine in detail the 3-dimensional velocities and water level elevations of the upper Derwent Estuary, with particular focus on the Tasman Bridge region. The model robustly reproduced tidal dynamics in the area, identifying water column stratification and the two-layered circulation near the Tasman Bridge, the southerly-directed surface fresh water and the northerly-directed near-bottom flow.

At the Australasian Coasts and Ports 2019, MetOcean Solutions’ consultancy team was also represented by Marine Project Consultancy Manager Dr Alexis Berthot and Senior Physical Oceanographers Simon Weppe and Dr Séverin Thiébaut. Find more about the studies presented at www.metocean.co.nz/news

The conference brings together engineers, planners, scientists and researchers to discuss multi-disciplinary issues related to coasts and ports. The 2019 Conference theme “Future directions from 40°S and beyond” reflects the increasing awareness about the need to find suitable means for adapting to change in the “right” direction. Visit coastsandports2019.com.au

The full abstract can be found here. For more information, contact us at enquires@metocean.co.nz

Surface current and surface salinity near Tasman Bridge. River flow from North to South.

Surface current and surface salinity near Tasman Bridge. River flow from North to South.