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Hi Gareth,
In my experience, using two different BC files Telemac2D and Sisyphe, is often necessary. For example, in hydrodynamics you need to define water level and velocities (ie LIHBOR, LIUBOR, LIVBOR: 5 6 6), whereas the respective LIEBOR, LICBOR, LIQBOR in SISYPHE have no prescription, thus are left free (4 4 4). However, as Michiel pointed out, it is pretty much critical to prescribe zero bed evolution at the boundaries (EBOR) so as to ensure your hydrodynamic boundary conditions remain within the defined scope.
In your case, having too much evolution at the boundary nodes is messing with your computation, hence fixing EBOR would do good. However you still need investigate the cause of the large evolution, which, given its extent, will inevitably cause problems downstream of the boundary.
Best Regards,
Costas

Hi cyamin

Thanks to your reply.
I saw in the forum earlier that it was suggested to use one BC file for Sisyphe and Telemac2D, this made me confused. I have conducted some cases to compare (using one BC file or two different BC files for Sisyphe and Telemac2D), and the results were similar.I think using different BC files is the right way to set up, so I am debugging based on this setting.
I am currently using 5 6 6 4 for Telemac2D and 5 4 4 4 for Sisyphe, which can't give a good result. I wiil try Michiel and your suggestion to fix the bed evolution to zero at the boundary (5 4 4 5 for Sisyphe) later.

Kind Regards
Gareth

Hello! I have the same problem with a simulation of sisyphe. I wanted to ask you if you could solve it with the boundary conditions? How could you solve it?

Thank you!

Hello! I use 5664 for Telemac2D and 5445 for sisyphe finally. The simulation result looks good.

Best wishes！