I used ArcHYDRO to prepare HydroDEM (5m) without sinks, Flow direction (FDR) raster, flow accumulation raster (FAC). As I understand FAC, value of pixel shows number of pixels that contribute to this pixel. Now, let say I derive drainage line from FAC (in raster form), I would like to link somehow all pixels that contribute to particular pixel in my drainage line, in way that I have separate contributing areas for each pixel in that drainage with clear relation to this pixel. How do I do that?

The main goal is to derive height difference between pixel in the drainge and any pixel that contribute to it and only to it.

1 Answer 1


Perhaps you are looking to calculate Melton Ratio.

If so, SAGA GIS has a tool to calculate it in the 2.1 Beta release.

If you've never used SAGA before, it can be a little intimidating, but the hydrology tools are well worth learning, and it's certainly easier than figuring out how to get ArcMap to do things it doesn't want to.

  • 1
    +1 for SAGA. I'm not looking for Melton Ratio, but I found an algrithm 'Vertical Distance to channel network', which suits my needs.
    – Tomek
    Commented Mar 30, 2013 at 22:47

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