I believe landslide is the correct term. ("Dispatched" is only used when a group of things, or people, are sent to do something). Landslide is still a newer word, so it's still thought of as two words, unlike a word like disdain (Which I recently realized comes from dis- and deign, a word 100% unused today). You might even see someone write "land slide" with a space. When I hear the word, I think more of a steep hill, where the top layer of sediment/rock gets loosened and rolls down. If that happened right under a road, that's probably what you'd get.