FAQ: When is the Set Flow Direction command enabled?
When is the Set Flow Direction command enabled?
Since flow direction cannot be set outside of an edit session, the Set Flow Direction command in ArcMap can only be enabled during an edit session. Also, if the current geometric network doesn't contain a junction feature class with a network AncillaryRole field, the Set Flow Direction command will not be enabled. You need to set the flow direction in a network after you create it, and again any time you change either the topology of the network or its sources and sinks. You can change the topology of the network by adding and deleting features, connecting and disconnecting features, or by enabling and disabling features.