I have a 3-level terrace in deep shade under mature oak and pine. The terraces are each appx. 45 feet long and 8 feet wide. When building each terrace using landscape ties, we inserted a drain along the length of each wall that exits at the ends of each terrace. (The top terrace exits into the middle terrace, the middle into the bottom, the bottom into the sloping yard.) The drain was covered with gravel, then 10 ton of topsoil was added to the terraces.

I haven't added plants yet because....

During a heavy rain, the terraces puddled up badly, becoming swampy, and even after three days the soil is still very wet and muddy. I don't understand why the drains aren't carrying the water away.

I'm planning to build up the topsoil with mulch and manure. Will that help? Any other suggestions?