An invasive species has been introduced into the catchment at a known location. This species is capable of moving in an upstream direction a maximum of 1km per week. Where could it have reached in 1 month?

WarningThe following guide is using a fictitious location and species...



Processing Task


You have prepared your river network and created a snapped point location where the invasive species was introduced into the river.

Invasive location


You could run the Create upstream nearby network tool 4 times incrementing the network length by 1000m to see the expansion of the invasive species over a month but such a task could be easily automated in model builder.



The create upstream nearby network was completed as shown below, note distance is an inline variable substitution from the FOR iterator.  Output is also being dissolved into a multi-part feature. Output is written to the Sites Geodatabase.

Create upstream nearby network tool


Although you never set the output name the tool does not overwrite an existing output it simply tags a numeric suffix. You can then add these layers back to the map and symbolise as needed.

 Week 1 - 1Km

Week 2 - 2Km

Week 3 - 3Km

Week 4 - 4Km

Week 1

Week 2

Week 3

Week 4


You could continue model logic and include downstream nearby network to see where the species could potentially invade in a downstream direction.  With the nearby network extracted as a spatial object you could involve it in further spatial analysis such as intersecting it with riparian data.

Return to top of page