[GRASS-user] watershed problem

[Charles Ehlschlaeger]

Here is the procedure I recommend (did this for a similar project many years
ago):
1) Rasterize river network to make RivNet.
2) Perform following r.mapcalc: newDEM = if(RivNet>0,DEM-10,DEM)
	This command ensures r.watershed uses RivNet to define basins.
3) Create basin map, Basin, using r.watershed with newDEM as input.
4) Use r.coin to determine which Basin values correspond to RivNet values.
5) Use r.reclass to create new basin map using RivNet values.

Chuck Ehlschlaeger, Associate Professor & GIS Center Director
Department  of  Geography,      Western  Illinois  University
215 Tillman Hall,   1 University Circle,  Macomb,  IL   61455
cre111 at wiu.edu,    phone: 309-298-1841,     fax: 309-298-3003


-----Original Message-----
From: grassuser-bounces at grass.itc.it [mailto:grassuser-bounces at grass.itc.it]
On Behalf Of ivan marchesini
Sent: Saturday, June 30, 2007 3:43 AM
To: grass user
Subject: [GRASS-user] watershed problem

Dear users...
I have this kind of problem to solve:

1)I have a point map (pointmap)
 
2)I have a vector river network (rivernetwork) of the main rivers of the
region (each segment has a code)

3) I have a DEM (DEM) of the area

I would like to assign to the pointmap the code of the firs river
segment on which each point of the pointmap hydrologically drain...

I need some suggestions on the process to create.... 
I can create a shell script ... but to do what?? 

I thougth to use r.drain into a shell script but I have two kind of
problems:
a) the elevations of the DEM are integer and r.drain stops when the flow
arrives to the alluvial plain, also after r.fill.dir is executed more
and more time...  
b) how can I find wich is the first segment of the rivernetwork wich is
crossed by the r.drain output???


I hope you can give me some hints!!!!!
thank you very much!!!!!

Ivan




-- 
Ti prego di cercare di non inviarmi files .doc, .xls, .ppt, .dwg.
Preferisco formati liberi.
Please try to avoid to send me  .doc, .xls, .ppt, .dwg files.
I prefer free formats.
http://it.wikipedia.org/wiki/Formato_aperto
http://en.wikipedia.org/wiki/Open_format

Ivan Marchesini
Department of Civil and Environmental Engineering
University of Perugia
Via G. Duranti 93/a 
06125
Perugia (Italy)
e-mail: marchesini at unipg.it
        ivan.marchesini at gmail.com
tel: +39(0)755853760
fax (university): +39(0)755853756
fax (home): +39(0)5782830887
jabber: geoivan73 at jabber.org

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