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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shall i use transport conditions per cell as I am using discharge per cell

Jakia Akter, modified 1 Year ago.

shall i use transport conditions per cell as I am using discharge per cell

Youngling Posts: 10 Join Date: 4/6/14 Recent Posts
Hi,
In my open boundary (river) of a delta system, I am using discharge per cell for flow conditions. For example, if I have 1000 cumec discharge in total, I am distributing it to 10 grid cells with 100 cumec. Now I am confused with my transport conditions at the same boundary. Shall I also distribute here the sediment transport? Or I have to give total sediment transport?
Thanks and kind regards
Jakia
Adri Mourits, modified 1 Year ago.

RE: shall i use transport conditions per cell as I am using discharge per c (Answer)

Yoda Posts: 1221 Join Date: 1/3/11 Recent Posts
Hi Jakia,

It depends on the level of detail needed in the area close to this boundary: If it's only needed for a correct water/sediment concentration far away then it doesn't matter. If more precision is needed, I advise you to use a boundary of type "Total Discharge" over the full width of the river being modelled. Then Delft3D-FLOW will take care of the distibution of water/sediment over the related cells. See section "9.4.1.2 Open boundary conditions" in the manual.

Regards,

Adri
Jakia Akter, modified 1 Year ago.

RE: shall i use transport conditions per cell as I am using discharge per c

Youngling Posts: 10 Join Date: 4/6/14 Recent Posts
Dear Adri,
Thanks for your reply. I got it. I think as long as I am using sediment concentration (kg/m3), so it should not impact the total transport load within the system.

May I ask you to refer me something where I will find how to calculate total load (million tonnes)? I wrote a code in Matlab for getting yearly total into cubic-meter from the trim file. By the way, I am using two types of sediments: noncohesive silty sand (200 micrometers) and cohesive mud (800 kg/m3 dry bed density with 0.5 mm of settling velocity). WOuld you please give me a simple calculation for 1000,000 m3 of sediment? I want to convert the amount into million ton.

I much appreciate your support.
Thanks and best regards
Jakia
Qinghua Ye, modified 1 Year ago.

RE: shall i use transport conditions per cell as I am using discharge per c

Jedi Council Member Posts: 612 Join Date: 3/2/11 Recent Posts
HI Jakia,

For sand, you may compute the total mass by: thickness*area of cells*density of sand(2650kg/m3 by default), or cumulative bed level change* area*density, while for mud, more or less the same, but you should make sure to use the correct dry density.

For sand, the diameter is not relevant and for mud, the settling velocity is also not relevant to compute mass.

Hope this is a little bit helpful,

Greetings,

Qinghua
Jakia Akter, modified 1 Year ago.

RE: shall i use transport conditions per cell as I am using discharge per c

Youngling Posts: 10 Join Date: 4/6/14 Recent Posts
Dear Qinghua,

It was helpful indeed. Thanks a lot.

Best regards
Jakia
Jakia Akter, modified 1 Year ago.

RE: shall i use transport conditions per cell as I am using discharge per c

Youngling Posts: 10 Join Date: 4/6/14 Recent Posts
Dear Qinghua,

I am confused with porosity and MorFac for calculating total sediment load. For my research work, I used sand with density 2650 kg/m3 and mud with dry density 800 kg/m3 over a 350kmX300km domain. My grid size is 500mx500m. So, first I calculated Mass of Sand/Mud per cell and then summed up all individual mass per cell according to the system polygon to calculate mass over an area (or system).
Mass of Sand per cell= T (thickness in m) * 500m *500m (area per cell which is fixed) * 2650 kg/m3 = 6.63*10^8 T kg = 0.663 T million tonnes; and
Mass of Mud per cell= 0.2 T million tonnes;
Now how to include MorFac and porosity in these calculations? Any suggestion is appreciated.

Thanks in advance.
Best regards
Jakia