Height Map: how to deleted unwanted faces? SupFolks!

I applied a height map to a plane and was wondering if there's an easier way that I can delete faces circle in red w/o doing it by hand.

Thanks in advance.


Heightmap

Unwanted faces circled in red
for 2.79 :in Edit Mode, hit numpad 5 to go to ortho view and hit either numpad 1 or 3 to get to perfect sideview then hit CTRL+tab and hit E to make Edge Selection then hit B to start the box selection tool hit X and select faces to deleted unwanted faces