Make Particles spawn and move on landscape

I’m currently trying to get a large crowd of animated skeletal meshes to walk using Niagara particles. The issue I’m having is finding a way to make the particles spawn on a landscape and then move along the landscape. At the moment they just phase through the hills of a landscape or hover over valleys.
I’ve tried Adding gravity and collision which just causes them to fall and stop moving once they hit the ground or finish sliding down a hill.
I’ve also tried exporting the landscape as a mesh and reimporting it to spawn the particles on a static mesh, but the filesize of the exported landscape is so huge that it crashes Unreal and Blender when I try to import it.

Because it’s niagara, you could try feeding it the heightmap of the landscape and having the particles change their Z manually based on the values from the heightmap multiplied by the same scale you set in the landscape…

Not necessarily the best way to go about anything really.

Do they give any better ideas in this one? Have yet to bother watching it.