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I'd like to delineate the catchments upstream of the sampling points.

In order to do that, I have done the following:

  1. Burn the rivers into the DEM using ArcHydro>DEM Manipulation>DEM reconditioning;
  2. Flow direction;
  3. Flow accumulation;
  4. Snap pour points (my sampling sites); and
  5. Watershed (Spatial Analyst>Hydrology)

However, the catchments I have got, don't match the reality. Could you please check the data through this link?

Any recommendations to get better results would be much appreciated.

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  • 2
    Your flow accumulation grid looks all messed up. Did you run a fill sinks on the DEM as the very first step? – Hornbydd Feb 15 '14 at 12:52
  • @Hornbydd Thanks for your comment. I haven't filled the sinks using Fill under Hydrology (Spatial Analyst). I have used Optimized Pit Removal Tool. I think this tool is more robust than Fill. I'd like to let you know that I downloaded the DEM using Global Mapper (SRTM Worldwide Elevation Data "3arc second resolution"). Afterwards, I have resampled it to 10m cell size (I have used Bilinear technique following you earlier recommendation not to use nearest technique) – aelwan Feb 16 '14 at 3:30
  • The catchment I'm working on it is in Samoa. If anyone knows a website a website from which I can download a higher resolution DEM, it would be great to share this website with me. – aelwan Feb 16 '14 at 3:35
  • I've looked at your datasets and the flow direction grid is very odd. I ran your dem through fill sink > flow direction > flow accumulation and snapped a pour point which you were having problems with and I was able to create the expected catchment boundary. Advice? Scrap what you got and start again as it looks like you have introduced errors into the flow direction grid. Try doing it without stream burning. – Hornbydd Feb 16 '14 at 13:52
  • Why mixing the spatial analyst tools with ArcHydro? I'd suggest you stick to one of them (ArcHydro is my favourite, more parameters to play with). – Martin Feb 17 '14 at 8:24

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