Hello,
You should study first a few test cases among those provided. There are several strange parameters in your case:
Coupling with Sisyphe for sediment (is it really what you want to do ?)
Period for drogues : do you have floating bodies ? This is dubious as you have no specific Fortran file.
Regarding the rainfall, I would try first the finite element option, I do not see any rain in the Finite volume part, maybe my colleagues could confirm that it is not yet implemented.
All in all I would suggest that you take an existing test case and just add rain into it.
With best regards,
Jean-Michel Hervouet