Heightfield particle collision?

[Jyochi]

Hi, I'm extremely new to Houdini and I'm trying to create sand winds like in here: 

My approach is to create particles (sand grains) that spawn on the heightfield, before being blown by a wind simulation or something (or instead of individual grains, just a smoke simulation)

What I have so far is a Procedural desert heightfield. I followed a tutorial to set up a smoke simulation that advects to a pyro,, but I'm struggling with setting up collisions and figuring out how to spawn the smoke/sand procedurally on the heightfield.

My pyro sim:

My heightfield:

Any help would be much appreciated! I can elaborate on any part so I can get advice better.