Inquiry regarding stratigraphic modeling and sediment transport in the Zhe-Min Muddy Coastal Area

[22320241151530]

I am currently working on a numerical simulation focused on the evolution of sedimentary strata in the Zhe-Min Muddy Coastal Area (East China Sea) during typhoon events. I would like to seek your professional advice regarding some technical configurations of my model:

Regarding Bedload Transport: Given that my study area is dominated by fine-grained cohesive sediments, is it acceptable to neglect bedload transport in this simulation? Or should it be included to account for extreme hydrodynamic conditions during typhoons?

Regarding Bed Layering Structure: To capture stratigraphic changes, I have configured a 30-layer bed structure as follows: 1 layer of 5 m, 4 layers of 1 m, 5 layers of 0.1 m, and 20 layers of 0.05 m. Based on your experience, is this vertical discretization reasonable for resolving event-driven deposition and erosion?

Regarding CPP Options: To effectively simulate stratigraphic evolution, which specific settings in the .h file (CPP options) should be prioritized?

Regarding Output Variables: For a detailed analysis of strata changes, what specific variables should be included in the model output (e.g., in the .nc history files)?

I would be extremely grateful for any insights or suggestions you could provide. Thank you very much for your time and expertise.

[jcwarner]

Glad to see you are using the sediment module. There are lots of options, and you may have to run several configurations to see what works best for your application.

-bedload: if your study is mostly cohesive material, then you can ignore this. It will also happen automatically because the bedload loop only works on the non-cohesive sediments (NNS), it does not work on the cohesive sediment (NCS). So when you list the sediment types, just use cohesive types.

-bedlayers: 30 layers seems like a lot. I am not sure exactly what you are trying to capture, such as river plume or remobilization of seafloor. But is suggest you try a smaller number, maybe 10, or 5 layers (?) just to see what happens. How much erosion do you expect?

cpp options:
you can start with what you have. the MIXED_BED and COHESIVE_BED are options for cohesive layers. If you only have cohesive, then just use the COHESIVE_BED, you wouldnt need the mixed bed.
Here is a link to a ppt on the sediment:
https://docs.google.com/presentation/d/ ... ide=id.p10

you can get to that same ppt with these steps:
https://github.com/DOI-USGS/COAWST/wiki ... -Trainings
click on 2021 Training
click on Thursday
Sediment_coawst_workshop is the ppt.

Output: you definitely want
Hout(ithck) == T ! bed_thickness sediment layer thickness

Hout(idmud) == T ! mud_01, ... suspended concentration
Hout(iMfrac) == T ! mudfrac_01, ... bed layer fraction
Hout(iMmass) == T ! mudmass_01, ... bed layer mass

and probably a few others. you will have to see what you are interested in.
-j

[ckharris]

HI

I agree with John's advice: I'd start with fewer layers; and you are probably going to need to do a few trial runs to see what works.

I'd set up the initial bed to have a big layer at the bottom with thinner layers on top; which it seems like you are doing.

Your header file says you will use the "mixed bed" which means you'll have some cohesive and some noncohesive sediment.

Another parameter that you might want to play with is "NEWLAYER_THICK" in the sediment.in file. Making this smaller (or bigger) will set the size of new sediment bed layers when your model needs to create them. I'd start with the default, do a trial run, and then decide whether it is a good value for the application.

Best wishes, Courtney