Questions tagged [r.watershed]

r.watershed is an R module that calculates hydrological parameters and RUSLE factors.

Filter by
Sorted by
Tagged with
0
votes
0answers
26 views

GRASS r.viewshed Command Line Error: Raster map <rasterfile> not found

I'm struggling to make sense of the grass command line syntax for specifying a raster geotif as an input parameter for a watershed analysis using a DEM tif. I may also have the user folder setup, ...
0
votes
0answers
80 views

r.watershed stream/rivers pixel size

I am using r.watershed to get a stream map (which I assume is rivers). However the output rivers is always 1 pixel wide. I would've assumed that if I run this on say Iraq I would see the Tigris and ...
1
vote
1answer
41 views

GRASS GIS change raster output size?

I have a large inut raster geotiff map of size 12000x9000. I am running r.watershed to output a stream raster map. However it is much lower resolution, only about 960x711. How do I make GRASS GIS / r....
0
votes
2answers
51 views

Why no need for “fill-sinks” when using r.watershed in GRASS QGIS?

I've seen a few places that when using the r.watershed function in GRASS QGIS, you do not need to use the "fill-sinks" procedure on the DEM before running the function. According to the ...
2
votes
2answers
48 views

Obtain channel/stream network from a DEM in QGIS

This might sound like a basic question, but running SAGA's Strahler order won't do the job for me. The lengths of the streams look way too short and this is quite a mountainous area. The result makes ...
0
votes
1answer
30 views

GRASS 7.8.3 problem with r.watershed and r.water.outlet

I need to find the basin of a small river and this is what I did: I found the drainage direction with r.watershed I used r.water.outlet to find the basin for the coordinates of the water outlet point....
0
votes
1answer
69 views

Flow accumulation from r.watershed creates discontinuous stream network compared with ArcGIS

I am interested in using r.watershed as integrated in QGIS for a course I teach, but am noticing discrepancies in the flow accumulation (facc) rasters and resulting stream networks that I get from ...
0
votes
0answers
9 views

Hillslopes tool from Whitebox GAT stuck in loop

I need to derive sub-basins from left/right side of a stream within a watershed and was very happy when I saw the Hillslope tool in Whitebox GAT since I have been having trouble with implementing the ...
0
votes
1answer
101 views

how can interior basins be modified in the r.watershed GRASS function?

This is a follow up question to How does "Minimum Size of Exterior Watershed Basin" work in r.watershed command in qgis 2.18.12? I understood that the threshold parameter is used to ...
1
vote
0answers
145 views

GRASS GIS: Getting know about stream power index (SPI) computation by r.watershed function

I need to know exact way how stream power index (SPI) is computed by module r.watershed. On the help page is that SPI is α * tan(β), where: α is cumulative upslope area draining through a point per ...
2
votes
1answer
565 views

Watershed Delineation Loop - r.water.outlet resulting in NAN area while snapped

I am attempting to create multiple watershed delineations for stations within a CSV file. I have files for flow direction (raster with a cell size of 30m), flow accumulation(raster with a cell size of ...
2
votes
1answer
1k views

How does “Minimum Size of Exterior Watershed Basin” work in r.watershed command in qgis 2.18.12?

I have delineated the watersheds from DEM using r.watershed command. I have specified the Minimum Size of Exterior Watershed Basin as 1500. I have read the description of r.watershed as well. I am not ...
1
vote
1answer
252 views

Getting error while executing grass algorithms from PyQGIS

I am trying to run r.water.outlet by PyQGIS but getting grass folder not configured error I have QGIS 2.18 installed and Grass is not installed on windows 10 and I am able to use r.water.outlet from ...
0
votes
1answer
88 views

R.Watershed unable to process a large geotiff (dem) file

I have a large geotiff file (dem) that I am planning to use with r.watershed to delineate a very large drainage basin. The file is 142 GB. When I try to run r.watershed after a few second it gives me ...
3
votes
1answer
1k views

Can't get GRASS r.water.outlet to work

I'm new to GRASS. We want to delineate a watershed using the LIDAR data we have our hands on. I tried to follow several procedures to do so, but despite all my efforts, I can only get it to select a ...
1
vote
2answers
918 views

G_malloc error while running r.watershed in GRASS 7.0.4

I tried to use r.watershed function in GRASS GIS, and got an error message ERROR: G_malloc: unable to allocate 3837384596 bytes of memory at raster/r.watershed/ram/init_vars.c:146 before getting the ...