Coast / Estuary

Coastal systems are among the most dynamic physical systems on earth and are subject to a large variety of forces. The morphodynamic changes occurring to coastlines worldwide are of great interest and importance. These changes occur as a result of the erosion of sediments, its subsequent transport as bed load or suspended load, and eventual deposition. 
Estuaries are partly enclosed water bodies that have an open connection to the coast. Estuaries generally have one or more branching channels, intertidal mudflats and/or salt marshes. Intertidal areas are of high ecological importance and trap sediments (sands, silts, clays and organic matter).
Within the Delft3D modelling package a large variation of coastal and estuarine physical and chemical processes can be simulated. These include waves, tidal propagation, wind- or wave-induced water level setup, flow induced by salinity or temperature gradients, sand and mud transport, water quality and changing bathymetry (morphology). Delft3D can also be used operationally e.g. storm, surge and algal bloom forecasting. 
On this discussion page you can post questions, research discussions or just share your experience about modelling coastal and/or estuarine systems with Delft3D FM. 




Sub groups
D-Flow Flexible Mesh
Cohesive sediments & muddy systems


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Overestimation of tidal asymmetry

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Overestimation of tidal asymmetry
estuary tidal asymmetry
Answer (Unmark)
4/11/18 9:07 AM
Hi All,
I'm having a tenacious problem with a Delft3D-model of a well-mixed meso-tidal estuary. The model consistently overestimates the amount of flood asymmetry inside the estuary, quantified in the m4/m2-ratio of the vertical tide. The overestimation also shows in comparison between measured and modelled tidal discharge curves; the modelled flood period is shorter than the measured period, and has a higher maximum.

I've tried a lot of things to remedy it:
- double check the determination of tidal constituents (it checks out; both model and measurement span the exact same period for consideration)
- double check the bathymetry and geometry of the model (it checks out; M2-amplitudes, phases and tidal volumes are ok)
- vary the time step and spatial resolution (no effect)
- vary the bottom roughness over the domain (no effect on the asymmetry)

I'm running out of things to test and knobs to turn. Does anyone have any idea why a Delft3D-model might overestimate tidal asymmetry like this?

Thanks anyway,