I have a customer who asked me to fix the water run-off problem in their backyard. There is a pretty good slope to the side yard and the water runs down into the backyard causing washouts. I was thinking the best way to remedy this problem would be to build at least one retaining wall to slow down the water about halfway down the backyard at the bottom of the hill, in effect tiering the backyard. This would hopefully fix this runoff problem and still keep the yard manageable for the customer to maintain. I figured with a drain behind the wall that could channel the water through the wall and kind of control the flow better than just allowing the water to run full speed down the hill and hit the backyard, hopefully the wall would kind of break up the flow of the water and slow it some. Thoughts?