Cutting topographic data below a polyline

[SimonClark]

Context: I want to cut  *.xyz data for a river channel below the free surface. 

I assume I want to use ArcGIS to generate a polyline based on my free surface data, and to clip out all topographic data that exceeds it. However, this isn't a method I've used before and it's been a long time since I've used ArcGIS. I've not found a method online either. Does anyone know where I could start, or what tools would be applicable?

Thanks in advance!

[SimonClark]

Thanks Xander,

I've snapped the points to the centre-line, however I'm still at the early stages of learning python (I only recently started a course) so in terms of processing the data I'd be on unsteady ground.  What would I need to write to process the data?

[XanderBakker]

Sorry for the delay. We're having the Colombian User Conference at this momento that has consumed a lot of my time. 

If you could share a small part of you data (or some dummy data with the same schema) I could explain it a bit better and provide some example code. 

[SimonClark]

Not to worry, that's fine. Would you rather me email you or message you on here (if that's possible - looking at the DM it looks like you can only attach links and pictures?)

[XanderBakker]

If you attach it directly to this thread, you will enable other to collaborate too. I think that would be better.

[SimonClark]

Hi all,

Please find attached a sample of my data, zipped to *.rar

It contains 6 files:

- the *.xyz topography

- the channel polygon

- the channel centreline

- original free surface data

- free surface data snapped to the centre-line (for both top and bottom banks, separately)

Many thanks!