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Screen shotUsing a point layer of 8,375 inlets and a DEM, how do I create an inlet drainage basin layer with contiguous basins, each delineating water drainage for and into each inlet? I used an integer DEM, from which I used the Flow Direction tool to make an input flow direction raster. Then I used the Watershed tool which took the input flow direction raster and the feature pour points (from the inlets layer) to create an output raster which I thought would yield contiguous inlet drainage basins but there's a lot of blank space between the basins (see screen shot), much more than make up the basins themselves. I would think it would look like patchwork adjacent polygons (leaving no areas of the DEM blank) showing surface drainage into one of inlets at any given point.

  • Welcome to GIS SE! As a new user be sure to take the Tour to learn about our focussed Q&A format. Are you using ArcGIS Desktop or something else to do this? – PolyGeo Jun 18 '18 at 22:58
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    Can you edit your question to show what the results are and what you are wanting, a simple screen shot with a sketch should do. – Hornbydd Jun 19 '18 at 10:15
  • I'm using ArcGIS Desktop Advanced 10.5.1 in Windows 10 64-bit. In particular, I'm using Spatial Analyst Hydrology tools. I added a screen shot. – mclemons Jun 19 '18 at 23:27
  • If I am not misteken, that happens becuase your inlets are not on the streams, so you get the subcatchment areas of very tiny tributary surface, not the main ones. Could you plot your point over the accumulation raster? – Marco Jun 20 '18 at 12:53
  • Thanks, Marco. I want to get catchment basins from surface flow that flows into inlets only. That's why I didn't include streams or pipes. But maybe I'm looking at in incorrectly. You requested that I plot the inlets over the accumulation raster and I'm not sure what you meant. Do you want a screen shot? – mclemons Jun 21 '18 at 17:19

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