Your network contains multi-part polylines

• Multi-part polylines are often the result of data capture.

Example 1

• A classic situation is where digitising has captured the boundary of a lake along with the inflow and outflow.  The resulting feature is a multi-part polyline.  The image below shows a multi-part polyline "exploded" into its individual parts, as you can see the middle part (2) forms a loop.

Part 2 in the image above still needs to be converted to a single centre line for the lake to ensure correct network connectivity.  If the image above was a river braid instead of a lake boundary; the wrongly digitised multi-part polyline (part 2) would need to be split into 2 lines, left and right channel.  So what you do with a multi-part polyline depends upon what is was capturing.

Example 2

• A multi-part feature is shown below. The first image shows the polylines with their direction of flow, one polyline is not showing the expected logical direction of flow

• Selecting the polyline shows up an unusual selection.

• Entering edit mode and setting task to modify feature shows the vertices. You could then use the sketch properties () dialog to explore the order of the vertices.

• Click here to learn how to explode multipart shapes.

• Once you have edited your data you must rebuild the node ID values of the attribute table.  You will want to use the newly created node fields for stream ordering.