We have a pool water-feature in front of the Timber fence. please refer to the photos attached. We built the water-feature box in block-wall and covered it with coping tiles and stone feature tiles...But in doing so we haven't built the back wall against the timber fence...which now needs to be taken care. We want to keep the timber fence and somehow protect the fence as we wanting to fill the box with soil to create a garden bed. I was considering putting builders plastic along the fence line in the hopes of stopping the wet soil from the garden bed coming into contact with the fence. Would that help or would it make it worse because water can not freely drain? What other options do we have to achieve the garden bed...we tried putting potted plants but they don't last long. so we wishing to plant Heliconia Tropicana's palms which would grow 2-3m tall as seen in photo.
(Heliconia Tropicana's ) 
Heliconia Tropicana's
(Water feature from outside) 
Pool Water feature front
Pool Water Feature from side
(Water feature from Inside)
Inside of the water feature
