I have a stream reach catchment raster and polygon layer generated via the archydro workflow with a user defined stream network. I would like to create a watershed hierarchy (levelled watersheds) from the catchments layer. It would be something like the HUC watershed hierarchy for the USA. How can I combine the reach catchments into hydrological units of increasing basin size? Is there some way to use stream order to assign pour points? Is there an archydro tool that can do this in an automated way. My area of analysis is very large, so manual placing pour points is not an option. I am using ArcGIS 10.4.