I am trying to simulate tidegates with SWMM EXTRAN. I am using the I2 card to specify an outfall with a tide gate. I am also using the J cards to input tide stages and times at the outfalls with tidegates. I have a few questions on how the tidegate option works.

1. The tidegate prevents backflow, does this mean that flow is discharged only when the tide is below the level of the tidegate?
2. What controls the opening and closing of the tidegate?
3. Should head losses due to the tidegate be included or are the minimal?

Any other ideas on using a tidegate would be appreciated.