Mesh to surface - terrain (relatively large size)

[AndersDeleuran]

You could also implement the GHPython script I link to here:

Water Flow on Surface

Not sure if this is helpful, but might inspire some ideas: I recently re-wrote a simple “particle descending down a surface/mesh drainage”-type script (that looks like a similar approach to your first example) for use on a project, and extended it with what is essentially a heat map visualisation of the drain polylines density (second image in the Instagram post): I basically snap the drainage polyline vertices to the nearest face center in the heat map mesh, and then count how many points a…

Or the terrain analysis components from Gismo:

GitHub - stgeorges/gismo: Gismo is a free Grasshopper plugin for GIS...

These both work with meshes.