[GRASS-user] minimum basin size for output from r.terraflow

[Dylan Beaudette]

On the topic of watershed basin delineation...

In preparing a small demo for my labmates, I was asked about the best way to 
delineate watershed basins at various scales with an algorithm like 
r.terraflow. With r.watershed, it is possible to define a minimum basin size, 
which can act as a scaling parameter. As a quick hack, I attempted to 
replicate this by vectorizing the output from r.terraflow and then using 
v.clean to remove basins smaller than some threshold. The results were 
largely similar to the basins produced by r.watershed, but in some cases the 
purely vector-based approach to "scaling" the basins resulted in questionable 
output (not surprisingly). 

So is there any logical way to define a minimum basin size for modules like 
r.terraflow - or does that construct even make sense for such algorithms [1].

1. noting that the concept of a watershed basin actually occurs at all scales, 
and is most likely fractal in nature.

Cheers, 


-- 
Dylan Beaudette
Soils and Biogeochemistry Graduate Group
University of California at Davis
530.754.7341