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

spatially non-uniform cohesive sediment settling velocity

IS
ILGAR SAFAK, modified 7 Years ago.

spatially non-uniform cohesive sediment settling velocity

Youngling Posts: 4 Join Date: 5/9/11 Recent Posts
I am working on calculating transport of cohesive sediment with size varying throughout my domain. This can be achieved by defining spatially non-uniform settling velocity for cohesive sediment in the model. Is this possible to do?

The interface allows to select files for non-uniform erosion rate, initial sediment layer thickness, critical stresses for erosion and sedimentation of cohesive sediment (and the manual discusses these, too), but not for its settling velocity. The manual does not say anything about the non-uniform settling velocity for cohesive sediments, it says "spatially varying d50 is possible for sand" (Table B.6, page 542), but the only property the interface allows to select files for non-uniform non-cohesive sand is initial sediment layer thickness. I can define the sediment in my domain as non-cohesive, and try to generate a spatially varying d50, but the code is giving the error below when I have my d50 (63 microns), i.e., the code wants the sediment to be defined as cohesive for d50<100 microns.


*** ERROR d50 < 0.0001 not allowed
*** ERROR Flow exited abnormally


Could you let me know whether settling velocity for cohesive sediment can be defined spatially non-uniform?
Roderik Hoekstra, modified 7 Years ago.

RE: spatially non-uniform cohesive sediment settling velocity (Answer)

Youngling Posts: 22 Join Date: 2/22/11 Recent Posts
Hi Ilgar,

If you want to apply spatially varying settling velocities, define different cohesive sediment fractions, each with its own settling velocity. Subsequently you can define the initial conditions (concentration or availability at the bottom) for each fraction seperately. This allows you to set-up a simulation with spatially varying settling velocities.

You can use this approach to define spatial variability of non-cohesive fractions as well, but in terms of the d50 parameter instead of the settling velocity for cohesive fractions.

Good luck!

Regards,

Roderik
Kyssyanne Oliveira, modified 2 Years ago.

RE: spatially non-uniform cohesive sediment settling velocity

Youngling Posts: 13 Join Date: 9/4/13 Recent Posts
Hi All,
I'm trying to model the resuspension of mixed (cohesive plus noncohesive) sediment in a continental shelf that has carbonate and terrigenous sediment. Basically, I have to vary spatially four classes of sediment: terrigenous mud, terrigenous sand, carbonate sand and carbonate gravel.

I saw that spatial varying D50 (SedDia file) can only be used with one sediment fraction in the model. So my doubt is how I can set all these sediments in my model. I also saw that the .sdb file would be used, but I'm a little confused on how to do this.

Thank you for your attention.
Cheers,
Kyssyanne Samihra