[GRASS-user] Define breaklines in DEM creation - r.surf.nnbathy

[Luís Ferreira]

At page 235 from book "OPEN SOURCE GIS - A GRASS GIS Approach" 3rd
edition:

"Natural neighbor interpolation is implemented in addon module
r.surf.nnbathy. It uses “nn” – a natural neighbor interpolation library
and allows the user to define breaklines such as stream lines or ridges
as 2D lines without the need to define their elevation"

http://www.sieczka.org/prog/grass/r.surf.nnbathy.html 

I searched for more information on how to implement 2D stream breaklines
in a DEM creation but I haven't found anything relevant.

Can someone help me?

Thank you

Luís Ferreira