[GRASSLIST:6201] Water basin filling w Grass

Hi all,

I'm doing research - a water body simulation with Grass. I
successfully created DTM w Grass (Hooray!) and now need to do more
specific things.

I need to find maximum possible water level for lake. I have place
where must be a lake and I need to know what water level is maximal
until it starts to spill out. And I need to find those spill out
points and levels (height).
I know it is possible, because I saw a demo on web but w/o HOWTO.
http://skagit.meas.ncsu.edu/~helena/gmslab/viz/erosion.html

Any help, ideas welcome :slight_smile:

And another question - I was following Grass tutorial (
http://www.ing.unitn.it/~grass/docs/tutorial/english/index_en.htm )
and creating basins with r.watershed but on low land it produced
thousands of small and narrow, parallel basins and result was not even
close looking to sample shown on tutorial
(http://www.ing.unitn.it/~grass/docs/tutorial/english/dtm4_en.htm). I
understand, that different data give different results, but not so
different!
Or its OK and I was just confused by beautiful results shown in this tutorial?
(See attachment.)
Grass 6.0.0 b2

TNX for reading,
Maris.

(attachments)

rst_test1_16.jpg

Hi,
tnx for idea about teraflow. I will try it. I'm newbie - so its hard
to find best tools for doing jobs :slight_smile:

But second idea would not fit to my needs - I don't have any border
polylines for lakes - I need to find out possible lake locations,
maximum possible water levels and potential spill out points. All I
have is DTM and notes on some areas where possibly where lakes.

Yeah, I know it sounds crazy, but I have only some month to write
paper for my MSc :wink:

Maris.

On Thu, 17 Mar 2005 17:19:38 +0100, Massimiliano Cannata
<massimiliano.cannata@supsi.ch> wrote:

For flat areas you can give a try to r.terraflow that manage this situation
with a different approach.
For find the maximum heigth to have a spill maybe you have to find the
lowest point around the border of the lake,
just an idea (probably stupid!): you can convert the border polyline to
raster, with r.mapcalc get the heigth of the dem in the corrispondence cell
and then with r.stats see the lower heigth in the map.
v.to.rast ....input=lake_border_polyline output=border
r.mapcalc 'dem_border=if(border,dem)'
r.stats dem_border

Hello!
Max

Māris Nartišs wrote:
Hi all, I'm doing research - a water body simulation with Grass. I
successfully created DTM w Grass (Hooray!) and now need to do more specific
things. I need to find maximum possible water level for lake. I have place
where must be a lake and I need to know what water level is maximal until it
starts to spill out. And I need to find those spill out points and levels
(height). I know it is possible, because I saw a demo on web but w/o HOWTO.
http://skagit.meas.ncsu.edu/~helena/gmslab/viz/erosion.html Any help,
ideas welcome :slight_smile:

And another question - I was following Grass tutorial (
http://www.ing.unitn.it/~grass/docs/tutorial/english/index_en.htm ) and
creating basins with r.watershed but on low land it produced thousands of
small and narrow, parallel basins and result was not even close looking to
sample shown on tutorial
(http://www.ing.unitn.it/~grass/docs/tutorial/english/dtm4_en.htm). I
understand, that different data give different results, but not so
different! Or its OK and I was just confused by beautiful results shown in
this tutorial? (See attachment.) Grass 6.0.0 b2 TNX for reading, Maris.

--
_____________________________________________________

Ing. Massimiliano Cannata

SUPSI - Istituto Scienze della Terra
C.P. 72 - CH-6952 Canobbio (Ticino, Switzerland)
Tel +41 (0)91 935 12 25 - Fax +41 (0)91 935 12 09
mailto:massimiliano.cannata@supsi.ch
http://www.ist.supsi.ch

Hi, In that case you may extract isoline from dem, get area and and then select the ones with a quota attribute lower than a value....
that will be the area filled by water at the select value level.....
Or r.mapcalc can do the trick.... r.mapcalc 'areafilled=if(dem<100)' a map of 0-1 where quota is lower or higher then 100m.

Hi,
Maxi

Māris Nartišs wrote:

Hi,
tnx for idea about teraflow. I will try it. I'm newbie - so its hard
to find best tools for doing jobs :slight_smile:

But second idea would not fit to my needs - I don't have any border
polylines for lakes - I need to find out possible lake locations,
maximum possible water levels and potential spill out points. All I
have is DTM and notes on some areas where possibly where lakes.

Yeah, I know it sounds crazy, but I have only some month to write
paper for my MSc :wink:

Maris.

On Thu, 17 Mar 2005 17:19:38 +0100, Massimiliano Cannata
<massimiliano.cannata@supsi.ch> wrote:

For flat areas you can give a try to r.terraflow that manage this situation
with a different approach.
For find the maximum heigth to have a spill maybe you have to find the
lowest point around the border of the lake,
just an idea (probably stupid!): you can convert the border polyline to
raster, with r.mapcalc get the heigth of the dem in the corrispondence cell
and then with r.stats see the lower heigth in the map.
v.to.rast ....input=lake_border_polyline output=border
r.mapcalc 'dem_border=if(border,dem)'
r.stats dem_border

Hello!
Max

Māris Nartišs wrote: Hi all, I'm doing research - a water body simulation with Grass. I
successfully created DTM w Grass (Hooray!) and now need to do more specific
things. I need to find maximum possible water level for lake. I have place
where must be a lake and I need to know what water level is maximal until it
starts to spill out. And I need to find those spill out points and levels
(height). I know it is possible, because I saw a demo on web but w/o HOWTO.
http://skagit.meas.ncsu.edu/~helena/gmslab/viz/erosion.html Any help,
ideas welcome :slight_smile:

And another question - I was following Grass tutorial (
http://www.ing.unitn.it/~grass/docs/tutorial/english/index_en.htm ) and
creating basins with r.watershed but on low land it produced thousands of
small and narrow, parallel basins and result was not even close looking to
sample shown on tutorial
(http://www.ing.unitn.it/~grass/docs/tutorial/english/dtm4_en.htm). I
understand, that different data give different results, but not so
different! Or its OK and I was just confused by beautiful results shown in
this tutorial? (See attachment.) Grass 6.0.0 b2 TNX for reading, Maris.

--
_____________________________________________________

Ing. Massimiliano Cannata

SUPSI - Istituto Scienze della Terra C.P. 72 - CH-6952 Canobbio (Ticino, Switzerland) Tel +41 (0)91 935 12 25 - Fax +41 (0)91 935 12 09 mailto:massimiliano.cannata@supsi.ch http://www.ist.supsi.ch

--
_____________________________________________________

Ing. Massimiliano Cannata

SUPSI - Istituto Scienze della Terra
C.P. 72 - CH-6952 Canobbio (Ticino, Switzerland)
Tel +41 (0)91 935 12 25 - Fax +41 (0)91 935 12 09
mailto:massimiliano.cannata@supsi.ch
http://www.ist.supsi.ch