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

 

 

Message Boards

Water level error

NB
Nophi Biton, modified 7 Years ago.

Water level error

Padawan Posts: 38 Join Date: 8/1/13 Recent Posts
I am trying to simulate a storm surge along a coast.
I have a bathymetry of the domain that ranges from 0 - 150 meters of depth (there are also some negative values for above mean sea level elevation near the coast)
My question is that what appropriate initial condition for water level should I use as an error saying "ERROR Water level change too high > 25.00 m (per 0.5 DT) after 30 timesteps in the following points:" ( the points mentioned are the leftmost column of the rectangular domain)

Also is 25 meter an upper limit boundary for difference of the initial and the computed?? What does the initial water level condition really for? Is this the water level along the coast or the average for all depth along the domain??

Can anybody help me in this forum as I am still learning this software for my research.

best regards,
Nophi
U
Arnold van Rooijen, modified 7 Years ago.

RE: Water level error

Hi Nophi,

The initial water level is the water level that you apply throughout your domain before you run your simulation. So when you start your simulations this initial water level will be influenced by water motions at your model boundary (water level variations, currents), wind and/or waves.

The error that you got means that the water level difference between two computational timesteps is unrealistically high (so it is not with respect to your initial water level). There can be several reasons for this error, e.g,. it might be something in your boundary condition, or it could be that your computational time step is too large for the processes you are modeling.

Cheers,
Arnold
Qinghua Ye, modified 7 Years ago.

RE: Water level error

Jedi Council Member Posts: 610 Join Date: 3/2/11 Recent Posts
Hi Nophi,

Also check your bathymetry as well. If there are strange deep points, the model might also be not stable.

Greetings,

Qinghua
NB
Nophi Biton, modified 7 Years ago.

RE: Water level error

Padawan Posts: 38 Join Date: 8/1/13 Recent Posts
Thanks a lot for the suggestion, you're right I observed the points mentioned in the error and indeed those are with abrupt change in depth.

Thanks a lot this forum is really giving me a lot of help learning delft3D

Nophi
NB
Nophi Biton, modified 7 Years ago.

RE: Water level error

Padawan Posts: 38 Join Date: 8/1/13 Recent Posts
Arnold van Rooijen:

The initial water level is the water level that you apply throughout your domain before you run your simulation. So when you start your simulations this initial water level will be influenced by water motions at your model boundary (water level variations, currents), wind and/or waves.


Thanks for answering my question, now you say its the water level throughout the domain, water level in reference to what (mean sea level)? so does it mean I can use an initial water level condition equal to zero (assuming the water level is the mean sea level)? Am I getting it right? then if not what is the basis of inputting an initial water level condition?

thanks a lot for answering my question, I appreciate your help.

thanks
Nophi
U
Arnold van Rooijen, modified 7 Years ago.

RE: Water level error (Answer)

Hi Nophi,

The reference level is something you can choose yourself, as long as all your model input (initial conditions, boundary conditions, bathymetry) is given with respect to the same reference level.

If mean sea level is your reference level (which in most cases it is) you can definitely set the initial water level to zero (so you're right). Just make sure that the water levels at your boundary conditions are also relative to MSL, and of course your bathymetry should be too.

Cheers,
Arnold