OpenBridge does not seem to have a dedicated functionality for drainage system. I have seen solution in OpenBuildings, it looks quite decent. Just to clarify, when I refer to a drainage system, I mean elements like drip pipes, scuppers, vertical pipes attached to the abutment, horizontal pipes attached to the deck, and so on.

Functionality in OpenBuilding i refer to:

https://www.youtube.com/watch?v=-1qJYHeusO8