.....I am in the process of replacing a retaining wall made from 3x4 rounded landscaping timbers. Its about 4ft high and 50ft long with a 4x4 dead-man structure built into the yard. We're replacing it because some of the facing landscaping timbers are rotted out.

.....The wall had no drainage system when it was built 15 or more years ago. I was going to simply install new facing timbers and put sheet plastic along the inside of the wall as a water barrier along with a drainage ditch at the top (12-18" deep & wide with leach-bed pipe and downspouts) to control run off.

.....Will this work or do I have to dig the entire structure out and put gravel and drainage behind the entire wall? Or should I just put it back the same way it was?