The "Add Alignment as Outlets" menu option allows a vector layer containing a polyline to be used to define outlets. Catchment outlets will be added automatically along this alignment whenever the upstream flow accumulation (i.e., catchment area) exceeds a threshold value. A cluster tolerance can also be set to group pixels located within close proximity together as a single outlet instead of separate outlets.
This tool is useful for automatically mapping catchments for all stream crossings of a road or railway alignment.