[GRASS-dev] [GRASS GIS] #2981: r.watershed & blocking

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1

#2981: r.watershed & blocking
---------------------+-------------------------
Reporter: mankoff | Owner: grass-dev@…
     Type: defect | Status: new
Priority: normal | Milestone: 7.0.4
Component: Raster | Version: 7.0.1
Keywords: | CPU: OSX/Intel
Platform: MacOSX |
---------------------+-------------------------
I'm not sure if this is a bug, but I think so. When I set the
{{{blocking}} option to {{{r.watershed}}}, I see no difference in the
accumulation map.

The example below, which should work on the NC data set, creates a
"blockage" at 30 m, runs {{{r.watershed}}} with and without the blockage,
and compares results.

{{{
r.contour input=elev_srtm_30m@PERMANENT output=z_30_v levels=30
v.to.rast --overwrite --verbose input=z_30_v type=line output=z_30_r use=z
--overwrite
r.mapcalc "rain = 1"
r.watershed -s -a --v elevation=elev_srtm_30m accumulation=acc
drainage=fdir flow=rain
r.watershed -s -a --v elevation=elev_srtm_30m accumulation=acc.block
drainage=fdir.block flow=rain blocking=z_30_r
g.gui.mapswipe first=acc second=acc.block
}}}

Also discussed at https://www.mail-archive.com/grass-
user@lists.osgeo.org/msg31665.html and
https://gis.stackexchange.com/questions/187310/what-does-the-blocking-
option-do-in-grass-r-watershed

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Ticket URL: <https://trac.osgeo.org/grass/ticket/2981&gt;
GRASS GIS <https://grass.osgeo.org>

2

#2981: r.watershed & blocking
------------------------+-------------------------
  Reporter: mankoff | Owner: grass-dev@…
      Type: defect | Status: new
  Priority: normal | Milestone: 7.0.4
Component: Raster | Version: 7.0.1
Resolution: | Keywords: r.watershed
       CPU: OSX/Intel | Platform: MacOSX
------------------------+-------------------------
Changes (by martinl):

* keywords: => r.watershed

--
Ticket URL: <https://trac.osgeo.org/grass/ticket/2981#comment:1&gt;
GRASS GIS <https://grass.osgeo.org>

3

#2981: r.watershed & blocking
------------------------+-------------------------
  Reporter: mankoff | Owner: grass-dev@…
      Type: defect | Status: new
  Priority: normal | Milestone: 7.0.4
Component: Raster | Version: 7.0.1
Resolution: | Keywords: r.watershed
       CPU: OSX/Intel | Platform: MacOSX
------------------------+-------------------------

Comment (by mmetz):

Replying to [ticket:2981 mankoff]:
> I'm not sure if this is a bug, but I think so. When I set the
{{{blocking}} option to {{{r.watershed}}}, I see no difference in the
accumulation map.

The `blocking` option only affects RUSLE-related outputs `length_slope`
and `slope_steepness`. Slope lengths are calculated from drainage paths
through the terrain. Path tracing stops as soon as a blocking cell or a
stream cell is encountered.

--
Ticket URL: <https://trac.osgeo.org/grass/ticket/2981#comment:2&gt;
GRASS GIS <https://grass.osgeo.org>

4

#2981: r.watershed & blocking
------------------------+-------------------------
  Reporter: mankoff | Owner: grass-dev@…
      Type: defect | Status: new
  Priority: normal | Milestone: 7.0.5
Component: Raster | Version: 7.0.1
Resolution: | Keywords: r.watershed
       CPU: OSX/Intel | Platform: MacOSX
------------------------+-------------------------

Comment (by martinl):

Can we close, update manual, or?

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Ticket URL: <https://trac.osgeo.org/grass/ticket/2981#comment:4&gt;
GRASS GIS <https://grass.osgeo.org>

5

#2981: r.watershed & blocking
------------------------+-------------------------
  Reporter: mankoff | Owner: grass-dev@…
      Type: defect | Status: closed
  Priority: normal | Milestone: 7.0.5
Component: Raster | Version: 7.0.1
Resolution: invalid | Keywords: r.watershed
       CPU: OSX/Intel | Platform: MacOSX
------------------------+-------------------------
Changes (by mmetz):

* status: new => closed
* resolution: => invalid

Comment:

Replying to [comment:4 martinl]:
> Can we close, update manual, or?

It is already mentioned in the manual.

--
Ticket URL: <https://trac.osgeo.org/grass/ticket/2981#comment:5&gt;
GRASS GIS <https://grass.osgeo.org>