[GRASS-user] Seed deposition along drainage lines

[Rainer M Krug]

Hi

I want to calculate the following:

1) I have a DEM
2) I have a raster layer of number of seeds
3) The seeds will be dispersed by water, i.e. following flowpaths calculated
by r.flow or r.drain (or similar)
4) depending on the slope, a certain percentage of the seeds are deposited.

I can create the flow lines using r.flow, calculate the cells through which
it would flow using r.drain (I can safely assume that all seeds do not
disperse further then 100 cells, so I can space the ones analysed in each
step to avoid overlap of the drainage lines), but what then?

I did it in R, but it was really slow, i.e. tracing from each cell
successivly the flowpath and depositing the seeds. So what I would need is
something like r.drain, where the value of each cell is calculated on an
underlying grid and the value of the cell "upriver", or, using r.flow, to
identify the initial cell, and, using the slope, to calculate from the
initial cell to the final cell the number of seeds deposited.

Is that possible, or is there a more efficient way of doing this? I have to
do this in a simulation for a rather large area, 50 to 100 times per
simulation and each simulation will be repeated several hundred / thousand
times (on a cluster, but anyway.).

Thanks,

Rainer
-- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation Biology,
UCT), Dipl. Phys. (Germany)

Centre of Excellence for Invasion Biology
Stellenbosch University
South Africa

Tel :       +33 - (0)9 53 10 27 44
Cell:       +33 - (0)6 85 62 59 98
Fax (F):       +33 - (0)9 58 10 27 44

Fax (D):    +49 - (0)3 21 21 25 22 44

email:      Rainer at krugs.de

Skype:      RMkrug
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