[GRASS-user] SRTM r.watershed at multiple scales

[Jennifer Corcoran]

Michel~

Thank you for your response, though I have taken a long time to say so.  I
am coming back to this now, and would like to take you up on your offer to
look at your script. I am familiar with python, but I am inexperienced with
implementing it within GRASS, so that will be a good challenge.

Please let me know what you think about it,

~Jennifer



On Wed, Aug 21, 2013 at 4:18 AM, Michel Wortmann <wortmann at pik-potsdam.de>wrote:

> 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.
>>
>>
>>
>>
>>
>> --
>> View this message in context: http://osgeo-org.1560.x6.
>> nabble.com/SRTM-r-watershed-at-multiple-scales-tp5072884.html
>> Sent from the Grass - Users mailing list archive at Nabble.com.
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>
>
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