Putting gravel in is one thing, but at the bottom of this trench is there a french drain? Or rather where does the water go?
If you have compacted top soil up to the wall itself water may drain over the top. If you dig out a trench, the trench will fill up like a pond. If you've got thirsty plants on the top, moisture may not be so much an issue... until winter. Many ifs and buts.
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If you have compacted top soil up to the wall itself water may drain over the top. If you dig out a trench, the trench will fill up like a pond. If you've got thirsty plants on the top, moisture may not be so much an issue... until winter. Many ifs and buts.