Drainage Tools toolbar, click the 
Auto Gullies properties button.
This option has settings for the general properties of a road.
On the Drainage Tools toolbar, click the Auto Gullies properties button.
The Auto Gullies properties window is shown.
Tick this option to show the gullies in the plan and 3D views, or untick to hide the gullies. This option is the same as toggling the DRAINAGE_GULLIES layer in the Layers Window.
This is the horizontal distance between consecutive gullies along a channel line and stops gullies being automatically placed too close to another.
Auto gullies will by default put double gullies at low points. Unticking this option will change all low points to a singular gully.
This is the subtended angle in degrees between the gully conduit and the sewer pipe it connects to. The default is 45 degrees but if you wanted the gullies to connect at right angles then you would change this angle to 90 degrees. This value is ignored if the gully conduit connects to a manhole.
Auto gullies will only connect to the sewer network if the point it would connect to is within this distance of the gully. This distance defaults to 15m and it sets the threshold at which it will not look any further to connect.
The outgoing conduit from the gully pot is not at the invert of the gully but at a specific level under the road surface to maintain reasonable structural cover above the pipe. The values defaults to 0.6m (600mm) and changing this value will either make the head of the gully conduit shallower or deeper under the road.
When a gully connects to the sewer system, the gully conduit will check to see if the gradient of the gully conduit is steep enough so as not to silt up or even flow in the wrong direction. The value defaults to 1 in 100 gradient, but please note the gully conduit will likely be much steeper than this gradient as it simply denotes the slackest gradient that is allowed before the gully will fail to connect to the sewer system.
This is the diameter in meters of the conduit that connects a gully to the sewer system and defaults to a 0.15m (150mm) diameter pipe.