Change Terrain Height Mid-Game?

is it possible to change terrain height mid game?

you can use terrain deformations, but that's all.
and i had heard that it can make some lag

Also you have to be careful with your actions then.
When you're using deformations they can cause desync with the usage of GetLocationZ().

Only if a player has a low graphic resolution on his warcraft options.

oh, i meant like cliff heights. guess i should have clarified. can't make boxed in cliffs mid-game like you can in editor?

no.