AnsweredAssumed Answered

An issue regarding Flow Direction from a PhD student

Question asked by redskies421 on Feb 19, 2016
Latest reply on Feb 24, 2016 by Playa



I am a PhD student in the UK and my project currently involves assessing how a certain species selects habitats. One variable of mine that is incredibly important (towards the species) regards water systems (mostly rivers and streams). So, I have a DEM (30 metre resolution) and from that, I was able to create a river and stream map for the area (as there is no available data on these variables for that region). Here is exactly what I did:


  1. got the DEM (30 m resolution and used fill)
  2. used the fill data to get flow direction
  3. flow direction to flow accumulation
  4. used raster calculator to assess accumulation grid (log10 ("accumulation grid data")
  5. took that log10 accumulation data (thus showing the smaller drainage areas)
  6. considered hill slope via raster calculator CON(log10data >=2, log10data)


So, that actually worked for the most part. I forgot to mention that there is an old map with river and stream systems and they match up very well. However! There is one huge issue. It turns out..the saltpans in the area (which I guess are very flat, although, I never visited them) have been completely distorted. When I complete the watershed analysis, it essentially, creates a huge (and weird) region where the saltpans are filled. I have asked a GIS specialist at my department and he was unsure how to fix this. my projections are correct, and in so far, I cannot think on how to fix this. I'v attached some photos (and links to photos) below that display my results. I have been pondering about this for quite some time and any suggestions would be incredibly appreciated.



these are the saltpans


[here is the flow direction pic][/img]