[GRASS-user] r.watershed

[Shane Carey]

Yep, I like that also - for me though - you can see the big rivers in the
hillshade but it is clearly not picking them out! Any ideas why this is? Is
the threshold value very important do you know?

Thanks

On Wed, Dec 6, 2017 at 1:11 PM, Mark Seibel <mseibel at gmail.com> wrote:

> Hi.
>
> I just used the tutorials from this page https://grasswiki.osgeo.org/wi
>> ki/Creating_watersheds to extract the stream network - however it could
>> be more accurate so was wondering is r.terraflow a better option for me. I
>> was using r.watershed originally
>>
>
> I've found r.watershed to be the most accurate, for our work. We've field
> verified the streams and its really solid data. I like that r.watershed
> doesnt alter the terrain since the LiDAR point data captures terrain
> nuances so well.
>
> Mark
>
>
>
>
>> Do you know why sink filling is needed for r.terraflow and not for
>> r.watershed?
>>
>> Thanks.
>>
>> On Wed, Dec 6, 2017 at 11:42 AM, Marco Alicera <marco.alicera at gmail.com>
>> wrote:
>>
>>> How did you add culverts?!
>>> Such a great question and I also wonder how you did. Short ago I knew
>>> about Itzï and its ability to do it with SWMM
>>> http://itzi.readthedocs.io/en/latest/tutorial.html#culvert-modelling.
>>> Looking forward to testing it
>>> --
>>> Marco
>>>
>>> 2017-12-06 9:24 GMT+01:00 Shane Carey <careyshan at gmail.com>:
>>>
>>>> Hi Mark,
>>>>
>>>> Thanks for your reply! Sounds great.
>>>> How did you add culverts or other artificial flow control features to
>>>> achieve water flowing through roads?
>>>>
>>>> I have a rivers layer and I compared it the streams I've obtained from
>>>> r.watershed and r.watershed appears to not match these streams (which were
>>>> accurately digitised) and I was wondering if I had a better resolution DTM
>>>> would it solve this problem?
>>>>
>>>> Also, why is sink filling needed for terraflow and not watershed?
>>>>
>>>> Thanks for your help :-)
>>>>
>>>> On Máirt 5 Noll 2017 at 23:43, Mark Seibel <mseibel at gmail.com> wrote:
>>>>
>>>>> Hi Shane.
>>>>>
>>>>> I'm happy to report that I've modeled overland water flow with
>>>>> r.watershed for over a quarter million acres, consisting of several large
>>>>> project sites, at 1 meter DEM resolution. The data source was LiDAR
>>>>> points to make the DEMs.
>>>>>
>>>>> At this resolution, it becomes necessary to add culverts, or other
>>>>> artificial flow control features, to achieve water flowing through a road.
>>>>> Otherwise, water is routed along roads until a lowest point is reached for
>>>>> crossing.
>>>>>
>>>>> I also use r.terraflow outputs as ancillary data to help drop in
>>>>> culvert locations and help provide guidance in problem areas.
>>>>>
>>>>> My geographic area is central Florida, which is very flat and full of
>>>>> topographic depressions known as wetlands. These depressions interrupt the
>>>>> stream network continuity in reality, but r.watershed does a fantastic job
>>>>> making a continuous drainage network model, especially in these difficult
>>>>> areas.
>>>>>
>>>>> Happy Modeling!
>>>>>
>>>>> Mark
>>>>>
>>>>> On Tue, Dec 5, 2017, 3:49 PM Shane Carey <careyshan at gmail.com> wrote:
>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> I am trying to extract river network from a 5m DEM with some success
>>>>>> using r.watershed. Has anyone tested this algorithm on high resolution
>>>>>> LiDAR data for example - 1meter DTM and what kind of results have they
>>>>>> obtained?
>>>>>>
>>>>>> Thanks
>>>>>>
>>>>>> --
>>>>>> Le gach dea ghui,
>>>>>> *Shane Carey*
>>>>>> *GIS and Data Solutions Consultant*
>>>>>>
>>>>> _______________________________________________
>>>>>> grass-user mailing list
>>>>>> grass-user at lists.osgeo.org
>>>>>> https://lists.osgeo.org/mailman/listinfo/grass-user
>>>>>
>>>>> --
>>>> Le gach dea ghui,
>>>> *Shane Carey*
>>>> *GIS and Data Solutions Consultant*
>>>>
>>>> _______________________________________________
>>>> grass-user mailing list
>>>> grass-user at lists.osgeo.org
>>>> https://lists.osgeo.org/mailman/listinfo/grass-user
>>>>
>>>
>>>
>>
>>
>> --
>> Le gach dea ghui,
>> *Shane Carey*
>> *GIS and Data Solutions Consultant*
>>
>
>


-- 
Le gach dea ghui,
*Shane Carey*
*GIS and Data Solutions Consultant*
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