[GRASS-user] r.damflood question

[Moritz Lennert]

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