I have a costumer who wants their backyard leveled out.. Problem is... one side is a good 6' higher then the next. There is a lot of run off water from winters and rain storms that flows right through the middle. The customer wants the backyard to be as level as possible. I was thinking we could put a drainage system through the low part u shaped part from high point all the way to the low point of the property.. How do I landscape this property without building up the one side to much?