Hi jencor808,
I can only recommend using SRTM for subbasin delineations. We are using
it on a regular basis in our hydrological modelling working group.
You'll have to play around with thresholds a little. I use different
thresholds for different areas of my catchment (eg. in mountainous
regions I'd want smaller subbasins). By masking those areas and run
r.watershed several times, you can vary your thresholds and then patch
the different subbasin rasters back together. As the r.watershed
algorithm often leaves small areas at the edges uncovered, you'll have
to fill those before or after patching, otherwise you'll have holes in
your subbasin map. You can also get rid of small subbasins by converting
your subbasin raster into a vector map and then run
v.clean remove small areas (check manual)
Hope it helps. I have got a python/GRASS script that is station-based
that does the varying thresholds for you and all the cleaning etc. Let
me know if you'd want to give that a try.
Regards,
Michel
On 08/16/2013 06:51 PM, jencor808 wrote:
Hello all~
I'm working with SRTM data and trying to produce watershed maps in Honduras.
For most of the country, the threshold seems to work great at 100000, but
this is not the case on the shore - those watersheds are neglected likely
due to their smaller scale. Does anyone have experience merging multiple
scales? Does this make sense? I'd rather not reduce my threshold or the
whole country because those watersheds seem too small.
As an aside, what do people think about using SRTM for watershed mapping in
the first place - given it is a surface model and not a DEM.
--
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