A great diorama of a Buffalo Jump. I had the great pleasure of visting 'Head-Smashed-In' buffalo jump near Calgary when I lived in Canada and they had a full scale reproduction of the event.
The only difference as I understood it, was that most of the Buffalo Jumps were used before the natives had access to horses. They waited until the herd was in the right position and a few hardy souls crept up to the herd using used buffalo skins as disguise before jumping out and making enough noise to stampede the herd. The herd was funnelled into the jump by the rest of the tribe using screens of grass, smoke from fires and making a lot of noise to keep the buffalo heading towards the cliff.
However, your use of mounted figures to stampede the herd works and creates a much more dramatic effect.