Flow direction when there are cells with the same change in z in multiple directions?

Discussion created by miewinstrup on Mar 18, 2013
Latest reply on Mar 19, 2013 by miewinstrup
I have a DTM that I have filled with the Fill-tool (The depression is filled up to 9,90 m) and then used to calculate flow directions with spatial analyst, ArcMap 10.0.

In the DTM there are cells with same change in z-value in multiple directions and these are not part of a sink. According to ArcMap 10.0 help "the flow direction is assigned with a lookup table defining the most likely direction. See Greenlee (1987)", but unfortunately I don't have access to Greenlee 1987 (Greenlee, D. D. 1987. "Raster and Vector Processing for Scanned Linework." Photogrammetric Engineering and Remote Sensing 53 (10): 1383???1387).

I have attached a picture of my DTM with elevation and the derived flow direction, I would like to know if anyone know why the directions are assigned how the are for the red arrows???

Thanks in advance,
University of Copenhagen