Spatial join flowlines and catchments and avoidd non-overlapping flowlines and catchments in split.
Per #119 (closed) we should do a spatial join to see if flowlines and points of interest that are to be split are contained with the catchment boundary or not. If not, then we can't really do a split.
@abock do you think we should add a flag to the flowlines in nhd prep that indicates this or do it in navigate?
This can be closed once the issue identified in #119 (closed) is no longer present in the output.