I have an XPSWMM model of a neighborhood storm drainage system. Nearly all of the drainage is above ground through a network of ditches and culverts.

I still need to create catchments for the upstream points for each culvert so I can route runoff through the network. There are around 150 culverts, and the topography is quite complex, and doing this manually is quite time-consuming and complicated.

Is it possible to create somewhat of a network of subcatchments to snap to these points in QGIS?

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  • Perhaps you could divide the drainage network into subwatersheds (like how each HUC-10 is divided into HUC-12s), add subwatershed IDs to the culvert layer, and only query the network within the relevant subwatershed for each culvert. – csk Aug 6 '19 at 21:00
  • Please decide which of the software products you mention you wish to ask about in this particular question. By doing that you can tell us more about where you got stuck testing/researching it to address a particular requirement to make a sufficiently focused question. – PolyGeo Aug 6 '19 at 21:16
  • ArcGIS has a watershed tool which you can input your pour points. That should work, but I do not have the license to use that tool (or any Spatial Analyst tools). I was wondering if there is a free or cheap alternative that I can use in either ArcGIS or QGIS. – Lauren Alivia Morgan Aug 6 '19 at 21:22
  • You could have a look into the r.watershed and r.water.outlet and available in qgis. They will not produce automatically your expected output, but it will certainly speed up the production of the subcatchments of each culvert – Marco Oct 2 '19 at 7:36

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