Not sure what's going on since I've not seen this before. But have you tried different threshold values?
On Fri, Jul 13, 2018 at 2:06 PM Erin Hanan <ejha...@gmail.com> wrote: > Hello, > > I am new to the list; please let me know if my question should be > formatted differently. > > I have been running r.watershed on a large (>400 km2) basin using a 10 m > resolution dem. I am finding that it produces some half basins that are > either fragmented or very small (i.e., just a few pixels). This seems to > happen mostly in areas bordering the stream, though I do sometimes get half > basins that are also not connected to the stream. I'm attaching a zoomed in > screen shot that illustrates some very strange sliver and fragmented basins > that are bordering larger, more appropriately delineated half basins. In > this case, the inappropriate basins all border the stream. > > I have tried running r.watershed using GRASS6.4 and GRASS7. I have also > tried using SFD, MFD with a range of convergence values, and the -4 flag. > These options produced different half basin delineations, but the problem > with sliver basins and basin fragments has not gone away. > > I also checked the dem values for the inappropriate half basins, and they > are very similar to the values for neighboring normal basins. So at this > point, I'm not sure how to fix the problem. Any advice from the GRASS > community would be greatly appreciated. > > Thank you, > > Erin > _______________________________________________ > grass-user mailing list > grass-user@lists.osgeo.org > https://lists.osgeo.org/mailman/listinfo/grass-user
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