[GRASSLIST:879] Re: Flow Accumulation

[Jaro Hofierka]

Hi,

I don't remember exactly the methodology of Tarboton, but I think 
r.flowmd might be quite close to it. It is similar to r.flow except that 
it divides the flow to two adjacent downslope cells. So it has a small 
diffussion effect. Both r.flow and r.flowmd use the D-infinity algorithm 
in terms of flow direction defined by aspect, but just r.flowmd uses 
multiple-flow distribution (disperses the flow to more just 1 cell).
The main advantage of r.terraflow is that it contains very fast and 
efficient algorithms including depression filling, etc. Maybe you can 
compare these modules to see differences. Any improvement is welcome.

Jaro

SWlab wrote:
> Hello,
> 
> I tried several of the commands to compute flow accumulations (r.flow, 
> r.watershed,r.terraflow). It seems that in all cases, the algorithms are 
> either D8 (steepest slope), or D-multi (flow weighted among the dowsnlope 
> neighbors).
> I wondered whether there was any GRASS implementation of the D-infinty 
> algorithm (flow routed to a cardinal and a diagonal cells, depending on the 
> aspect. Ref: Tarboton, D. G., (1997), "A New Method for the Determination of 
> Flow Directions and Contributing Areas in Grid Digital Elevation Models," 
> Water Resources Research, 33(2): 309-319). 
> If not, I'd welcome any suggestion. [Processing the 'direction' output of 
> r.terraflow to find the dominant direction, and linking the aspect map ?]
> Thanks a lot in advance
> P.