[Qgis-user] Calculate upslope catchment areas for multiple points?

Mon Jan 15 00:52:50 PST 2024

If the outlet points are correctly positioned on the stream network (i.e.
you don't need to "snap" them to the streams) and you're able to install
and run GRASS addons, you should be able to just use r.accumulate with the
outlet= option to specify the layer of outlet points, and the subwatershed=
option to tell it to calculate watersheds.
If you want to run it as a QGIS processing algorithm, you'll need to create
a description file.  This is mine, but you don't need most of it if you're
not wanting to use other features of r.accumulate.:

On Mon, 15 Jan 2024 at 09:01, <qgis-user-request at lists.osgeo.org> wrote:

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>    1. Calculate upslope catchment areas for multiple points? (Ben Jones)
>    2. Re: Calculate upslope catchment areas for multiple points? (kirk)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sun, 14 Jan 2024 17:15:58 +1100
> From: Ben Jones <bmjones at iprimus.com.au>
> To: Qgis <qgis-user at lists.osgeo.org>
> Subject: [Qgis-user] Calculate upslope catchment areas for multiple
>         points?
> Message-ID: <0734D400-0095-4DAB-8C53-853157B5552F at iprimus.com.au>
> Content-Type: text/plain;       charset=utf-8
>
> Hello All,
>
> I have used SAGA to generate channel networks and r.watershed to generate
> catchment sub-basins from Copernicus 30 m DEM data to assist with planning
> a stream sediment sampling program. Once samples are collected I would like
> to generate polygons that define the upslope area for each sample point.
>
> I understand that this can be done using SAGA Terrain Analysis ?Upslope
> area? tool that requires manually copying and pasting the X and Y
> coordinates for each sample point (one point at a time which works but is
> not practical for 100?s of samples, or in batches which is still not ideal
> and doesn?t appear to work?).
>
> Is there an easy way to import a point file with multiple points (100?s of
> points) to SAGA or another tool to automatically calculate upslope
> catchment areas for each of the points?
>
> I have come across two potential solutions:
>
> 1) ?Qgis SAGA Upslope Area for several points automation?:
>
> https://gis.stackexchange.com/questions/342333/qgis-saga-upslope-area-for-several-points-automation
> 2) ?Snap pour points and delineate multiple catchments in QGIS?:
> https://www.youtube.com/watch?v=Hqc_1CMadhA
>
> However, both are three years old and it appears there are complications
> using both these methods in newer versions of QGIS3. Are there alternative
> methods?
>
> I am using QGIS 3.28.11a on macOS Monterey.
>
> Thanks,
>
> Ben
>
> ------------------------------
>
> Message: 2
> Date: Sun, 14 Jan 2024 09:48:54 -0400
> From: kirk <kirk at nortekresources.com>
> To: Ben Jones <bmjones at iprimus.com.au>, Qgis
>         <qgis-user at lists.osgeo.org>
> Subject: Re: [Qgis-user] Calculate upslope catchment areas for
>         multiple points?
> Message-ID: <1705240136977.2864c2306c2b3915 at nortekresources.com>
> Content-Type: text/plain; charset="utf-8"
>
> Hi Ben.The python script should work in your version since it is written
> in python 3.? It us,a relatively simple routine which iterates over each
> sample point and rund the saga tool.? It nay take a while to run 100s of
> points but it should finish.Saga is a third party, open source software
> suite that is developed independantly of QGIS.? It is very powerful and
> fast for most raster processing.? Saga also has native batch or scripting
> capability which may be an option for you.? Just a note that the module
> syntax can change? with versions. So and older script may not complete on a
> new release.Kirk SchmidtSent from my Galaxy
> -------- Original message --------From: Ben Jones via QGIS-User <
> qgis-user at lists.osgeo.org> Date: 2024-01-14  2:23?a.m.  (GMT-04:00) To:
> Qgis <qgis-user at lists.osgeo.org> Subject: [Qgis-user] Calculate upslope
> catchment areas for multiple points? Hello All,I have used SAGA to generate
> channel networks and r.watershed to generate catchment sub-basins from
> Copernicus 30 m DEM data to assist with planning a stream sediment sampling
> program. Once samples are collected I would like to generate polygons that
> define the upslope area for each sample point.I understand that this can be
> done using SAGA Terrain Analysis ?Upslope area? tool that requires manually
> copying and pasting the X and Y coordinates for each sample point (one
> point at a time which works but is not practical for 100?s of samples, or
> in batches which is still not ideal and doesn?t appear to work?).Is there
> an easy way to import a point file with multiple points (100?s of points)
> to SAGA or another tool to automatically calcu
>  late upslope catchment areas for each of the points?I have come across
> two potential solutions:1) ?Qgis SAGA Upslope Area for several points
> automation?:
> https://gis.stackexchange.com/questions/342333/qgis-saga-upslope-area-for-several-points-automation2)
> ?Snap pour points and delineate multiple catchments in QGIS?:
> https://www.youtube.com/watch?v=Hqc_1CMadhAHowever, both are three years
> old and it appears there are complications using both these methods in
> newer versions of QGIS3. Are there alternative methods?I am using QGIS
> 3.28.11a on macOS
> Monterey.Thanks,Ben_______________________________________________QGIS-User
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