[GRASS-user] r.stream.extract Montgomery

[stephen sefick]

What is good guidance for where to set the threshold?  I am in the
coastal plain, but In the very upper part ~10 miles from the piedmont,
so it is not terribly low gradient (I am going to quantify this "not
terribly low gradient" soon).  I don't see the -b flag for r.watershed
6.4svn checkout (probably a week ago) in the man pages.  I said
realistic because you can set the threshold to 1 for a 1m res dem.
There are lines that don't even look like streams all over the place.
Is it possible to extract streams with the landscape (Mongomery) as a
guide for the threshold?  I want to be able to do this so all of the
stream ordering is done on a consistent stream network among
watersheds.  If this is not possible then I will use a threshold and
use this for all stream network extraction on all of the other dems
that I need to process so they are all comparable.  I appologize if
this doesn't make sense, but I will explain in greater detail if I
need to.
kindest regards,

Stephen Sefick

On Thu, Aug 5, 2010 at 9:35 AM, Jarek Jasiewicz <jarekj at amu.edu.pl> wrote:
> stephen sefick pisze:
>>
>> I would like to use the Montgomery method to extract streams (exp~2
>> from the paper).  What should the threshold value be?  And in general
>> what should the threshold value be?  I am working in the southeastern
>> coastal plain (USA), which is characterized by low gradient (if this
>> helps).
>
> for flat areas Montgomery's method is not a good option. Generally that
> method was created and tested on areas with gradient > 5%.
>>
>>  I am using 1m resolution LIDAR data.  I would like to extract
>> the most realistic map of streams that I can.
>
> Chmmm... what you mean realistic? Maybe use existing stream network will be
> the best solution?
> For coastal plains where is no real vallyes the r.watershed's treeshold with
> -b option seems to be best option
>>
>>  I am also trying to
>> track down the inttermitance perminance threshold.  Any guidance would
>> be greatly appreciated.
>> kindest regards,
>>
>>
>
>



-- 
Stephen Sefick
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| Auburn University                                   |
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