how to analysis watersheds of terrain?

Do someone know that how to analysis watershed or catchment of terrain using grasshopper?

for example, input a terrain(or mesh） and divide it to some watersheds or catchments, then

calculate the area of every watershed. Thanx!

Replies to This Discussion

Permalink Reply by Daniel Piker on January 11, 2015 at 7:26am

Perhaps this old forum thread might be of use:

http://www.grasshopper3d.com/forum/topics/drainage-direction-script

Permalink Reply by oldstory on January 11, 2015 at 9:05am

thank you for your reply. I searched the forum many times:) There are some threads about drainage direction or rain runoff, but no one thread about Watershed area.

Permalink Reply by Riccardo Majewski on January 11, 2015 at 9:16am

Try to find something about 3D derives....

In 2D functions when the derived intersect with x axis (y=o) it means the original function have a mountain or a valley...

To subdivide your surface you need to find mountains...

Permalink Reply by oldstory on January 11, 2015 at 9:58am

in large scale, the watershed is enclosured with ridges of moutains. but I don't know how to find the ridge, maybe using the apect of terrain? in site scale, the variation of height is less, catchment is the area that the runoff have a single outlet. how to find a catchment associate with a specific outlet?

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