Description
Name of the addon
r.traveltime
Describe the bug
When using r.traveltime one would expect that every pixel in subbasin, created with r.watershed, flows to the outlet point, which is defined by the cell with the maximum flow accumulation value within the respective subbasin. Unfortunately this does not always work and the resulting traveltime-raster is often smaller than the the subbasin (see attached screenshot where the yellow part is not included in the traveltime rarster). What is the reason that some cells apparently never arrive at the outlet, although r.traveltime and r.watershed use the same input grids (filled DEM (r.fill.dir), flow direction and flow accumulation)?
To Reproduce
Steps to reproduce the behavior:
- Open the North Carolina dataset nc_basinc_spm_grass7
- Run following commands in the console (the outlet coordinates where derived manually):
g.region raster=elevation@PERMANENT
r.fill.dir --overwrite input=elevation@PERMANENT output=filled_dem direction=flowdir format=agnps
r.fill.dir --overwrite input=filled_dem@PERMANENT output=filled_dem2 direction=flowdir2 format=agnps
r.watershed -s -a --overwrite elevation=filled_dem2@PERMANENT accumulation=accu basin=subbasins threshold=10000
r.mapcalc "n = 0.035f" --overwrite
r.traveltime --overwrite dir=flowdir2@PERMANENT accu=accu@PERMANENT dtm=filled_dem2@PERMANENT manningsn=n@PERMANENT out_x=637757.00 out_y=218794.34 threshold=3000 b=1 nchannel=0.03 dis=1000 out=traveltime_99
Expected behavior
In a subbasin created with r.watershed every cell should eventually flow to the outlet and the traveltime raster, created with r.traveltime, should have the same size as the subbasin.
Screenshots
Screenshot is attached
System description (please complete the following information):
- Operating System: Linux Ubuntu 20.4
- GRASS GIS version 7.8.6
