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

Boundary conditions do not reflect the forcing of my model

IP
Ivenis Pita, modified 1 Year ago.

Boundary conditions do not reflect the forcing of my model

Youngling Posts: 7 Join Date: 12/20/17 Recent Posts

I have a problem that I am not sure how to solve it.

i am modeling a coastal bay in the southeastern coast of Brazil.

At first, I ran a model only with tide. I used astronomical boundaries obtained from Dashboard, however I observed that the values on the bca was not even close to the values observed on the first cell after the open boundary. Therefore, I decided to apply a correction on the boundary conditions (.cor file).  

 

Afterwards, I decided to perform a run with Hycom forcing my open boundaries, therefore I used a Riemann .bct. I obtained my bct file based on makeBctBccIni.m routine. Than, I faced the same problem. The values of the first cell after the open boundaries is significantly different from the Hycom output (figure attached). In this case, i am not sure if the problem is the generation of the bct file, or the modeling process itself.

IP
Ivenis Pita, modified 1 Year ago.

RE: Boundary conditions do not reflect the forcing of my model

Youngling Posts: 7 Join Date: 12/20/17 Recent Posts
Phil Shepperd, modified 1 Year ago.

RE: Boundary conditions do not reflect the forcing of my model

Padawan Posts: 45 Join Date: 12/4/18 Recent Posts

Those forcings don't look very "tidal" to me ..... just sticking with the Dashboard boundaries for now, what is the amplitude of the M2 and S2 constituents? My feeling is that the values in the .bct file are so small that there is more noise than signal, if that makes sense?

By the way, I can't see what roughness you are using, but try starting with a uniform Manning of say 0.02, or Chezy of 60, rather than a spatially varying file, just to get things running .......

IP
Ivenis Pita, modified 1 Year ago.

RE: Boundary conditions do not reflect the forcing of my model

Youngling Posts: 7 Join Date: 12/20/17 Recent Posts

That true, I forgot to mention that I was using hycom with no tide. So it is just subinertial processes going on there.

My point is that I should expect the blue line (DELFT data) to be more related to the black line (Hycom data), because my Delft run was based on hycom data and I am comparing a cell that is nearest to my boundary.

In respect of the rgh file (find attached), I also tried a uniform value of manning == 0.02 when running my first trials (with only tide), but there where no significant differences. Anyhow, I'll do a run using Hycom and uniform manning to check it out.

Phil Shepperd, modified 1 Year ago.

RE: Boundary conditions do not reflect the forcing of my model

Padawan Posts: 45 Join Date: 12/4/18 Recent Posts

So if no tide, what is causing the water level variations in the boundary data you are giving Delft3D?  Meteorology? Do you have suitable wind and pressure data also forcing the model?   In which case the internal solution of the model may be sensible, but you will struggle with comparison close to the boundary.   

IP
Ivenis Pita, modified 1 Year ago.

RE: Boundary conditions do not reflect the forcing of my model

Youngling Posts: 7 Join Date: 12/20/17 Recent Posts

The water level variations are driven by atmospheric data (CFSR), and meso scale features such as eddies and meanders. Hycom was forced by wind and pressure data, but I plan to run D3D with atmospheric forcing as well. 

 

I just don't understand why this problem related to comparison close to the boundary also occurred when I tried D3D with just tide. Because the variations were much bigger and the diurnal components presented an error of 90 degrees in phase.