Problem

Is there a way to model gutter flow that exits a system through a different outfall? In other words, the gutter flow would be diverted away from the downstream catch basin.

Solution

The gutter would need to be connected to a catch basin or an outfall. The screenshot below shows one possible configuration. 

The captured flow at the catch basin is directed through a conduit that eventually end at an outfall, called "Outlet" in the screenshot above. The bypass gutter flow, however, is directed in a different direction and out through a different outfall, here called "Outlet - Ditch". This is a valid configuration and would allow you to divert gutter flow to a different element.

See Also

How does StormCAD handle gutter flow from an active catch basin to an inactive catch basin?