Ok, iunderstand the need for the gravel base the gravel backfill and the lanscape fabric,..But what does the perforated pipe add ? my wall is 80 ft in lenght 3ft & under in ht,do i add just one pipe with no pitch or more than one?

Holes up or down? The slope runs north to south, south being the low point...How is running the pipe say west to east going to help?

I will be replacing the timbers with block wall.