[GRASS-user] Trento3D screenshots redone

[Jeroen Wortel]

Hi Markus,

Is the r.lake routine available?
We are doing some (simple) river inundation analysis as well;

we create a raster map of our vector river model with value 1, 
multiply this by the desired water (flood) height, add this to our 
DEM and use r.mapcalc to extract all cells lower or equal to the 
flood level. Then we convert this to a vector file, and extract the 
polygon containing the main stream and the connected flooded areas 
(which is one class as created by r.mapcalc).

This works quite ok, but tends to be slow when there are lots of 
islands (eg buildings) in the inundated area.

How does r.lake work? I couldn't find anything in the docs.

Thanks,

-Jeroen.


At 16:26 19-5-2006, you wrote:
>Tom,
>
>I didn't intend to make some real hydrological modeling. r.lake
>isn't written for that.
>
>In fact, it will be a good idea to connect to external models.
>E.g. the SWIG interface could be of help here.
>
>Markus
>
>On Fri, May 19, 2006 at 09:49:41AM -0400, Thomas Adams wrote:
> > Paulo,
> >
> > You're right about the need for modeling. Actually, the modeling would
> > be done outside of GRASS and then have the appropriate water surface
> > elevation data imported into GRASS to show the inundated areas. The
> > hydraulic modeling *could* be done withing GRASS, but a better first
> > step probably would be to do the modeling outside of GRASS and then
> > import the data. An additional advantage to this is that there are many
> > hydraulic models and one may have a preference as to which to use or,
> > not be restricted to a particular model, thereby retaining more 
> flexibility.
> >
> > Tom
> >
> >
> > pmarc wrote:
> > >2006/5/19, Thomas Adams <Thomas.Adams at noaa.gov>:
> > >>Hamish & Markus,
> > >>
> > >>How did you do the inundation? With r.lake; does this use a level
> > >>surface? If so, this is not correct for a river, due to the downstream
> > >>slope of the topography and the hydrodynamics of the flow. The resulting
> > >>water surface elevations would be less than a level surface. Channel &
> > >>overbank cross-sections are needed (corresponding to those used in a
> > >>dynamic flow model) which then need to be intersected with the
> > >>topography. The US Army Corps of Engineers HEC-RAS & HEC-GeoRAS software
> > >>that is integrated with ArcGIS does this correctly.
> > >
> > >Well, that was just to showcase possibilities and then you come with a
> > >class on hidrology!!
> > >
> > >Thanks!
> > >
> > >I think it should be easy to add a slope to that flood surface, but
> > >that would be still incorrect.
> > >The solution would be to implement a flood modelling routine, but
> > >then, this is the beauty of free software! However, with all my
> > >excitement about all this, I am not the person to implement it... I'm
> > >still lacking some work on the localization of GRASS....
> > >
> > >I think I speak for the whole community when I say we are glad to see
> > >GRASS being used is such hi-profile tasks.
> >
> >
> > --
> > Thomas E Adams
> > National Weather Service
> > Ohio River Forecast Center
> > 1901 South State Route 134
> > Wilmington, OH 45177
> >
> > EMAIL:        thomas.adams at noaa.gov
> >
> > VOICE:        937-383-0528
> > FAX:  937-383-0033
>
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