[GRASS-user] r.basins.fill usage

[Jarosław Jasiewicz]

Hi
try r.stream.basins from grass add-ons it has options (-c and -l flags) 
to generate subbasin without any manual work. Look also into tutorial on 
grass wiki about it (wiki -> dokuments ->r.stream.*

Jarek
Achim Kisseler pisze:
>> Based on this excerpt from the manual, it seems the main
>> external/perimeter watershed boundary, as well as the internal ridges
>> need inputted?  "The raster map layer depicting ridges should include
>> the ridge which defines the perimeter of the watershed. The coded
>> stream network can be generated as part of the r.watershed program,
>> but the map layer of ridges will need to be created by hand"
>>
>> My question is really about the need to manually digitize ridges
>> inside the watershed boundary delineated by r.watershed.  As opposed
>> to running r.watershed with a smaller threshold to get these smaller
>> basin delineations within a given study area.
>>
>> If one has to manually digitize the internal ridges in a watershed, I
>> wondered what the point of the module was.  It obviously has
>> application, but it seems I am missing something obvious.
>>
>> Hope that is more clear.
>>     
>
> Now its much clearer to me. Thanks.
>
> In my opinion the description ao r.basins.fill is now very detailed. I
> don't really understand it. So maybe someone else can help and maybe we
> could find out and enhance the description:
>
>
> I think this one:
> "r.basins.fill generates a raster map layer depicting subbasins, based
> on input raster map layers for the coded stream network (where each
> channel segment has been "coded" with a unique category value).."
> is clear.
> Input is: raster map X from "r.watershed stream=X"
>
> Not clear to me is:
> "...and for the ridges within a given watershed."
> which is explained as:
> "The raster map layer depicting ridges should include the ridge which
> defines the perimeter of the watershed."
> What should the parameter mean? How should that be stored in a raster-map?
> So try out:
> -> take the stream-network and run r.mapcalc:
>  r.mapcalc "perimeter=if(X,5,null)"
> Resulting map is a rastermap with value 5, where stream-network is not
> null. The five is raster-cells or map units or what else?
> -> run r.basins.fill with that and see what happens.
>
> I guess: from each network-segment the subbasin is created which has a
> minimum distance of 5 (cells?) to the stream. So its something like a
> buffer.
>
> ...in contrast to:
> "...but the map layer of ridges will need to be created by hand (for
> example, through digitizing done in v.digit)"
> => the ridges-map here is a vector-file!
>
>
> Achim
>
>
> PS:
> --%<--
> DESCRIPTION
> r.basins.fill generates a raster map layer depicting subbasins, based on
> input raster map layers for the coded stream network (where each channel
> segment has been "coded" with a unique category value) and for the
> ridges within a given watershed. The raster map layer depicting ridges
> should include the ridge which defines the perimeter of the watershed.
> The coded stream network can be generated as part of the r.watershed
> program, but the map layer of ridges will need to be created by hand
> (for example, through digitizing done in v.digit).
>
> The resulting output raster map layer will code the subbasins with
> category values matching those of the channel segments passing through
> them. A user-supplied number of passes through the data is made in an
> attempt to fill in these subbasins. If the resulting map layer from this
> program appears to have holes within a subbasin, the program should be
> rerun with a higher number of passes.
> --%<--
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