[MikeL]

You have three options to control the gates. Time series, elevation controlled, and navigation dams (I have never used this one).

You set these by going to your unsteady flow editor.

Then set a boundary condition by selecting the river and reach, and then the inline structure xs number. (I am assuming this is an inline structure)

Then click "add a boundary condition location"

Hopefully the location comes up farther down the window, then highlight the cell next to that location. Now the three options I talked about previously should be available under "boundary condition types". Select whichever one you want. There should be some guidance for these in the manual.

Hope this helps, and if I am unclear just reply back.