Hello,
I would like to waterproof the retaining wall in the photo. Around 10m long. Do I need to dig out all the dirt until I reach the footing? I'm aware this is the proper way but there is a garden I don't want to disturb and the area in the photo is already raised on a 1m wide, 1m high retaining. I wouldn't be able to dig out much. The plants have also grown twice in size.

Is there a product to use where I could dig out just a little (30cm max?) and apply the product to stop moisture from raising?
Thank you !