Now that you have a HydroNetwork you must assign the right flow directions to it to ensure consistent and complete connectivity.

The Flow Direction in a network is stored as an esriFlowDirection value for each Edge and may have the following values:

In the Arc Hydro data model the Flow Direction is assigned to each of the HydroEdges (in HydroEdge feature class) using the attribute value FlowDir. Thus, FlowDir may have any of the above values.

• FlowDir = 0 (Uninitialized flow direction)

• FlowDir = 1 (WithDigitized direction)

• FlowDir = 2 (AgainstDigitized direction)

• FlowDir = 3 (Indeterminate flow direction)

By using any predefined Flow table and/or doing some hand editing, the correct flow direction has to be defined for your network.

From experience we recommend the use of WithDigitized direction (=1)  for NHD or Terrain Analysis Derived Data or AgainstDigitized (=2) for the RF1 river network as a starting point and only to decide which direction captures most of the Flow Directions correctly so that you will minimize the hand editing work as much as possible.

Manually save flow direction in FlowDir Field in HydroEdge (Calculate value = 2 or 1 depending on the origin of your data)

Set Flow direction using the calculated FlowDir Field in HydroEdge

6.1-Place Flags and trace upstream

To make sure you have achieved complete connectivity perform some tracings on the HydroNetwork.

6.2-Make corrections on Flow directions (on FlowDir field) to get Complete Network Connectivity

Keep ALL the corrected ones SELECTED and Store Flow Direction

Set Flow Direction

6.3-Select Shorelines if any

If you have Shorelines, select ALL Shorelines and disabled them for computation purposes.

Assign FType = Shoreline

For the selected Shorelines set Enabled field = False

Go onto next phase