Yanis
The crash is logical.
You uncheck the "tidal flat" option and when the water level decrease downstream, some lateral nodes becomes dry !!!
The help for the keyword is clear:
When no, the specific treatments for tidal flats are by-passed.
This spares time, but of course you must be sure that you have no
tidal flats
Change this parameter and your computation will run.
One more remark, on the solid boundaries, Telemac-2d consider that there is a vertical wall, so it's not necessary to create lateral wall with the bathymetry...