Our family was looking for a way to enjoy our backyard in the evenings. We had an empty spot and decided on a patio with a fire pit. The problem was it was not a level area. After some research and planning we decided to embark on the journey ourselves as that is the only way we could afford it. Design and planning took several weeks and the build lasted two additional weeks. In the end we ended up with a beautiful fire pit area that we can enjoy for many years.
That was a great debate combined with lots of research. There was a lot of conflicting suggestions. Since the wall is only 16 inches at its highest I did not install a specific drain. I dug a trench and buried a course of block on top of 2 to 3 inches of gravel. The ground was covered with landscape fabric that I wrapped up all the walls. I backfilled with mason sand and gravel. All hand tamped as we went. We will see how it holds up. We had a really heavy storm shortly after finishing and did not notice any run off coming through the lower blocks. Hope that answers the question.