Parameters controlling the erosion in the morphodynamic model. - Forum - Riverlab
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- Parameters controlling the erosion in the morphodynamic model.
Parameters controlling the erosion in the morphodynamic model.
Niraj Bal Tamang, 3 Jaren geleden aangepast.
Parameters controlling the erosion in the morphodynamic model.
Advanced Augur Berichten: 34 Aanmelddatum: 26-4-21 Recente berichten
My morphodynamic model is of a mountain river reach so the erosion rate is really high. I tried feeding more sediment to make it aggrade but it is still flushing all the sediment in the upstream section (no bed change after certain timesteps) and depositing in the downstream boundary (changes occur throughout the timestep). I think the previous warning (not errors) saying "Bed change exceeds 5% of waterdepth" and "Sediment erosion shortage at.." are also caused due to this issue. This is not the field scenario as I am expecting some aggradation in the upstream section as well and along the reach too in some parts. I tried using ThetSD=0 and ThetSD=0.25 and Morfac=1 (for both) values to see if the bank erosion can bring any change. It did but my problem wasn't solved. Shall i just keep on adding the sediments until I see some aggradation in the upstream section or are there any other parameters which I can change to solve this. Thank you
Victor Chavarrias, 3 Jaren geleden aangepast.
RE: Parameters controlling the erosion in the morphodynamic model.
Famous Fortune teller Berichten: 97 Aanmelddatum: 24-4-20 Recente berichten
Before crashing numbers in a morphodynamic simulation I would first try to estimate the river's behaviour analytically. Based on the slope, discharge, friction, and width, one can estimate the flow depth and velocity. This can be compared to the hydrodynamic results. With this and the sediment transport relation you are using, you can estimate the sediment transport rate. You would expect overall aggradation when feeding more than this value and vice versa.
It is maybe interesting to start simple and increase in complexity. COnsdier first all the transport to be bedload and fix the upstream boundary condition. In this way you obtain a stable run and an estimation of the sediment transport rate that yields such a stable situation.
It is maybe interesting to start simple and increase in complexity. COnsdier first all the transport to be bedload and fix the upstream boundary condition. In this way you obtain a stable run and an estimation of the sediment transport rate that yields such a stable situation.
Niraj Bal Tamang, 3 Jaren geleden aangepast.
RE: Parameters controlling the erosion in the morphodynamic model.
Advanced Augur Berichten: 34 Aanmelddatum: 26-4-21 Recente berichten
Thanks a lot. I will try that way now. Previously, I took the results from the hydrodynamic run to get the maximum water depth at the uppermost cross-section at each timestep. Then I calculated the transport rate for that depth and river width at that cross-section using Wilcock and Crowe (2003) equation. Then I multiplied the sediment rate for each fraction such that they coincide with the water discharge hydrograph. Then I fed them in the morphodynamic model. The sediment erosion warning got less this time but the warning related to bedlevel exceeding 5% of water depth was still as before. I read your 2017 JGR paper on the equilibrium alluvial river under variable flow. My work seems somehow more related to this paper. Hopefully I can combine the ideas from here and your advice to feed in my model and make it work. Thanks once again.