Accepted Solutions
So, assuming I had a waterway feature like this:
I might create a line feature class like this:
Then distribute that feature class to all users, either via file or through a published feature service.
Each user can then work in their given segment, and as long as they make sure that their edits snap to the dashed line, they'll know that their work will not overlap with other users' edits.
Taking this a step further, you could create polygons of each segment. The polygon features would represent each user's assigned area, and could even be attributed as such.
It's at this point I realize I've only drawn 8 segments, not 9, but you get the idea.
Other thoughts
Now, I don't really know what work your team will be doing, or what your layers look like. If you were digitizing the waterway itself, that's where reference points would come in.
Adding a point on those "cut lines" where the bank is can give your users precise points to start and stop banklines so that the final merged product appears seamless. But again, that's if you were digitizing the bank lines and needed them to match up. Are you able to elaborate on the specific tasks users will be doing?
It's also possible that some segments prove easier or harder than others. It may be preferable to divide the work area into many segments, then use an external task managing tool for users to "grab" open tasks. When the first user finishes their initial segment, rather than waiting for the rest of the team to wrap things up, they would be able to take on the next open segment and continue working. Additionally, each individual segment feels shorter and more manageable.
