I have attached a picture of my vector stream layer in green and my watershed subbasin boundary in yellow.
What I have done up to this point is:
Buildwalls with watershed boundary as outside and subbasin boundary as inside walls(I set inner wall height to 500 and left inner wall buffer and breach line buffer as 0)
flow direction with streams (I have tried to run this function but am only getting error)
By looking at my stream layer and how it exits my subbasin in two places instead of one I am unsure of how to treat this. Any ideas? I thought flow direction with streams was my best option but it is not functioning.