You can use the Create reaches tool to construct a polyline from a snapped site to the river mouth. The results could be used for spatial analysis or visualising the route from the site to the mouth of the river network.

Eaxmple of reaches to the mouth

Three sites (red points) and the routes to their river mouth.

Work flow

1.Snap your sites to the river network; you can use the RivEX snap sites tool if you have many sites to process or simply move the site manually whilst ensuring snap to edge has been turned on.

2.Add a numeric field (type long) to your site data, call it something like SiteID. Populate this field with a unique numeric ID.  As an example you could run the Field Calculate tool setting your SiteID to equal the ObjectID.

3.Add a numeric field (type double) to your site data, call it distance.

4.Set the distance field to be a large value so you know it will reach the mouth of the river. For example, using the measuring tool you estimate the distance from mouth to be approximately 30Km. Thus a 50Km distance would certainly reach the mouth and account for the sinuosity of the river. This value does not need to be perfect just long enough to reach the mouth of the river. Important: your distance value must be in the the units of the river network. An example of such a prepared site table using the data above (the 3 red sites) would look as such:


5.Ensure you network is attributed with the source ID, this is a requirement of the create reach tool.

6.Run the create sites reach tool for a downstream reach, an example of the completed tool is shown below:


7.The tool will create the routes for each site to their river mouth. As you have set the distance to be further than the actual distance to the river mouth the route gets truncated at the mouth thus creating the desired route from site to mouth.