Dear Abin Philip :

I think that you would need to model this by defining sufficient cross sections that define the barrage. If the barrage is acting as another dam, downstream of the initial (upstream) dam, then you will need to model it as two dams in series.

If you have any additional questions or need any further information, please contact me again.

Sincerely,

Chris E. Maeder, M.S., P.E.
Senior Technical Engineer
chris.maeder@bossintl.com