intro story Coast / Estuary

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. 
 

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

 

 

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Help with Tidal Forces in Delft3D-Flow

RK
Rohit Kulkarni, modified 7 Years ago.

Help with Tidal Forces in Delft3D-Flow

Youngling Posts: 8 Join Date: 8/16/12 Recent Posts
Hi,

I had never activated the "Tidal Forces" before, and had to look into it for a project recently.

I couldn't get a clear view from the FLOW manual regarding this.

Chapter 9 of FLOW manual states:
Numerical models of tidal motion in coastal seas generally do not account for the direct local influence of the tide generating forces. The amount of water mass in these models is relatively small and the effect of these forces on the flow can be neglected. For coastal areas, the prescription of tidal forcing along open boundaries is sufficient in generating the appropriate and accurate tidal motion.
The need to model larger seashore areas with sections of the deep ocean or large closed basins has increased. In the numerical models of these areas the contribution of the gravitational forces on the water motion increases considerably and can no longer be neglected...

To check this I ran two simulations, with and without this process being activated. There was a negligible difference between the results. The model area is big enough (300 km X 250 km) to have significant tidal forces being active in the area. It also has a large variation between offshore and shallow area, with a large shallow basin.
Can someone please explain the exact difference between activating these forces and applying the astronomical tide at the boundaries only?