The World of Waterfalls has been to this waterfall, which you can read about here.

There is another way to witness Tarawera Waterfalls. By far the best way is via water taxi across Lake Tarawera. This deposits you at the lakes outflow where a good track broadly follows the river until the river begins to vanish. It is wonderfull geology and delightful native forest.

Eventually you descend the cliff face until you witness the river re-emerge half way down the rock face.

Everyone else takes the long drive route through the lower forest.