[GRASS-user] r.damflood question

[Codrina Maria Ilie]

Hi Moritz,

We had no real data for the lake bathymetry so we built it by 
artificially lowering the DEM values with a constant value. This is also 
the reason why the water depth is constant.

Regards,
Codrina


On 29/08/2017 00:29, Moritz Lennert wrote:
> Le Mon, 28 Aug 2017 17:05:01 -0400,
> Anna Petrášová <kratochanna at gmail.com> a écrit :
> 
>> Hi,
>>
>> On Mon, Aug 28, 2017 at 4:53 PM, Codrina Maria Ilie
>> <codrina at geo-spatial.org> wrote:
>>> Hi all,
>>>
>>> I have been trying to run GRASS7 module r.damflood using the
>>> following datasets
>>> [https://drive.google.com/drive/folders/0B2Yx_1shUSx3VThlY3BrV1JyWjg?usp=sharing],
>>> with this command:
>>>
>>> r.damflood --overwrite --verbose elev=dem lake=water_depth
>>> dambreak=dam_breach manning=manning tstop=3 deltat=1 h=b_depth
>>> vel=b_vel hmax=b_mwd vmax=b_mwv imax=b_mi wavefront=b_wf
>>>
>>> To make it easier, the lake has a constant depth.
>>>
>>> As far as I can understand, the rasters should be correctly built,
>>> but the outputs of r.damflood are obviously wrong (rasters with
>>> nodata or one category = 0; at second 1 the depth raster is half
>>> the lake's size (s00.png, s01.png)and at second 2, it completely
>>> disappears).
>>>
>>> During the processing, I get the Courant-Friedrich-Lewy stability
>>> condition warning message.
>>>
>>> If I try to chose as computational method for initial velocity
>>> estimation, uniform drop in of lake or small dam breach, I get the
>>> following error "ERROR: Don't find the dambreak - Please select a
>>> correct map or adjust the computational region".
>>>
>>> Does anyone have an idea what could be the reason of these results,
>>> please? Any suggestion would be highly appreciated.
>>
>> Your water_depth should have 0 instead of nulls, I think that's the
>> problem in your case. The stability condition warning probably means
>> you should reduce your time step, on the other hand, it will take more
>> time.
>>
> 
> r.null null=0 gets rid of the stability condition warning as well.
> 
> However, I don't know much about this module, but I'm a bit surprised
> by your DEM: IIUC, it's level is lower in the entire dam lake area than
> in the valley below. Also: is it normal that your water depth is
> constant all over the lake ?
> 
> Moritz
>