In order to ensure that you are able to accurately represent the stream network, you must ensure that the linework extends high enough in the watershed. In some cases, you may find that you want to extend the network beyond what is produced in the initial flow network.

If so, you have two options:

You can start over and re-delineate your flow network using a lower area threshold. But if you rerun that tool, everything you originally coded to a 1 is going to go back to a 0.
You could create another area threshold network, giving it a different name. Select the section that you want to add to your current flow network, and, using the append tool, add it to your original area flow network. This option will usually be the faster method.

Do not digitize what is missing. Never manually draw a line to add to your flow network. It won’t align to your LiDAR-derived flow direction and therefore you will not be able to run future tools to get your stream reach.

Stream Networks.JPG

While it is a time-consuming process, it’s very important that you do take your time through this process and make sure that you have every segment that you think could be part of the perennial network.