Opened 4 years ago

Closed 3 years ago

#2981 closed defect (invalid)

r.watershed & blocking

Reported by: mankoff Owned by: grass-dev@…
Priority: normal Milestone: 7.0.5
Component: Raster Version: 7.0.1
Keywords: r.watershed Cc: mankoff@…
CPU: OSX/Intel Platform: MacOSX

Description

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

Change History (5)

comment:1 Changed 4 years ago by martinl

Keywords: r.watershed added

comment:2 in reply to:  description Changed 3 years ago by mmetz

Replying to 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.

comment:3 Changed 3 years ago by martinl

Milestone: 7.0.47.0.5

comment:4 Changed 3 years ago by martinl

Can we close, update manual, or?

comment:5 in reply to:  4 Changed 3 years ago by mmetz

Resolution: invalid
Status: newclosed

Replying to martinl:

Can we close, update manual, or?

It is already mentioned in the manual.

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