[GRASS-user] footprint of a given volume of water.

GRASS GRASS user
1

Hi all,

I've used r.lake to answer the question "What land is inundated given
a X meter high dam?". In this case however, X is the unknown so I'm
trying to answer the question "How high does the dam have to be in
order to hold Y cubic meters of water?" as well as to determine the
"inundation footprint".

I'm familiar with some engineering models that require much more
detailed cross-sectional information than we have available...
currently we have a high-res DEM as our sole source. Are there any
GRASS modules or scripts that I should take a look at?

Thanks for the input,

--
Matthew T. Perry
http://www.perrygeo.net

2

Hi Matthew,

I would use r.mapcalc and calculate water volume slices from the deepest point of your basin in, say, 1 meter steps. As the resulting volume exceeds Y cubic meters of water (your threshold), you know how high your dam should be. This can be easily scripted. You can adjust the step size (1 meter) according to your accuracy needs.

-Jeroen.

On Fri, 2007-11-30 at 19:14 -0800, Matthew Perry wrote:

Hi all,

I've used r.lake to answer the question "What land is inundated given
a X meter high dam?". In this case however, X is the unknown so I'm
trying to answer the question "How high does the dam have to be in
order to hold Y cubic meters of water?"  as well as to determine the
"inundation footprint".

I'm familiar with some engineering models that require much more
detailed cross-sectional information than we have available...
currently we have a high-res DEM as our sole source. Are there any
GRASS modules or scripts that I should take a look at?

Thanks for the input,
3

Jeroen Wortel wrote:

> I've used r.lake to answer the question "What land is inundated given
> a X meter high dam?". In this case however, X is the unknown so I'm
> trying to answer the question "How high does the dam have to be in
> order to hold Y cubic meters of water?" as well as to determine the
> "inundation footprint".
>
> I'm familiar with some engineering models that require much more
> detailed cross-sectional information than we have available...
> currently we have a high-res DEM as our sole source. Are there any
> GRASS modules or scripts that I should take a look at?

I would use r.mapcalc and calculate water volume slices from the deepest
point of your basin in, say, 1 meter steps. As the resulting volume
exceeds Y cubic meters of water (your threshold), you know how high your
dam should be. This can be easily scripted. You can adjust the step size
(1 meter) according to your accuracy needs.

As the relationship between height and volume is monotonic, you can
use bisection, which will be faster.

--
Glynn Clements <glynn@gclements.plus.com>