Yes, tidal barrage is possible. I'm surprised this is not already on the forum.
As for the methodology, I've listed a few references:
Xia, J., Falconer, R. A., and Lin, B. 2010. Hydrodynamic impact of a tidal barrage in the Severn Estuary, UK. Renewable Energy, 35:1455-1468.
Xia, J., Falconer, R. A., and Lin, B. 2010. Impact of different operating modes for a Severn Barrage on the tidal power and flood inundation in the Severn Estuary, UK. Applied Energy, 87:2374-2391.
This should guide you in the right direction.
For Telemac, using Fortran would be your best solution. I've done this a while back: I've modified SOURCE_TELEMAC2D,PROXIM,UTIMP_TELEMAC2D and DEBSCE.
I've attached a fortran file however I don't have a simple example right now. I might have time this week to create and share a simple example. Hope this help...for now.
Kind regards,
Julien