•The enforce route to source option changes the behaviour of the algorithm and will influence any linking.  You can use this option if your site dataset has the sourceID encoded into it. You can find out about this here.


•With this option enabled and the appropriate field selected RivEX will only consider TO sites on the same source ID as the FROM site. 


•This can affect the output differently in an upstream or downstream direction when attempting to link sites.


The influence of enforcing source ID when linking in an upstream direction


•The nearest site upstream may be on a tributary but this will be ignored if the route to source (the source ID) is different. In this case RivEX will continue traversing upstream along the route to source (always the same source ID) and may not even find a site upstream.


•If you want to find the next nearest upstream site on the same stem as you FROM site then turn on this option.


The influence of enforcing source ID when linking in an downstream direction


•The route to source ID will change as  RivEX traverses down stream as sub catchments feed into large catchments. If the source ID changes before the next nearest down stream site is found then no sites will be linked to as they are on a different route to source.


•If you want to find the next nearest downstream site then turn off this option.