Drainage from patio into retaining structure?

[drmrbrewer]

We are constructing a raised patio with retaining wall. There is a drop down to a lower bed (planting) and then down to ground level. This is illustrated in the section below.

In terms of discharging rainwater from the raised patio, would it make sense to have slots through the parapet in the first retaining wall so that rainwater can discharge into the bed below and then to ground level (as shown with solid arrows)?

Or more sensible (as shown in dotted line) to use a French drain and just allow the water to seep down into the retaining structure, and then through seep holes in the retaining walls and finally out to ground level? There is enough volume in the structure that I would imagine it wouldn't all flood down at once but would disperse and gradually seep out.

Another other ideas?

 

[Iwilldoit]

How about using connected pipe to take it through the bed wall at patio level and down through the bed soil to then exit at ground level.
I would be thinking that any plants will be getting too much water and the bottom of the ground level wall constantly wet may start to spall.

 

[drmrbrewer]

@lwilldoit might be tricky to do that without the pipes being visible? Is there anything fundamentally wrong with discharging rainwater into a retaining structure like this (I mean the main retaining structure under the patio, i.e. the dotted arrow approach... the retaining structure for the bed will always have rain falling into it so we can't really avoid that)? Is it asking for trouble?

 

[Iwilldoit]

Can you fill the bed a little more to hide the top of any elbow. Or have the drain on the face of the patio using a linier drain which has a exit on the bottom

 

[Iwilldoit]

I would be worrying about the build up of trapped water between the planter wall and your foundations of the house, so just as your dotted line but using a linier drain and pipes to send it to the lower ground level

 

[drmrbrewer]

Actually there is an existing drain on the house wall for the kitchen sink, which feeds to the mains drain. The patio level is being raised compared to where it is now, so I think there might be sufficient height drop to allow the patio to slope away from the house to the patio wall, then into a gravel french drain with a perforated pipe in the gravel drain, and then a solid pipe going back under the patio to the existing drain... any problems with this? See below.