How to design backyard drainage?

[lijithwv]

Hello members,

Need advice in managing drainage in the section of the backyard shown in the photos. The lot behind the fence is on the higher side (about 200mm at the higher side and around 100mm at the lower side) and the natural slope is from right to left. I have 600mm of gap between our concrete and the fence. I was initially planning to put up single sleeper retainers near to the concrete end. Then attach drainage mat on to the back of the sleeper and have 65mm socked agi pipe laid with gravel connected to stormwater system to manage water inflows from the lot behind. But that raises a question on how the water from our concrete path will be drained. Will the above plan work effectively for draining the water flowing out from our side? 

Another idea I was thinking was to push the sleeper retainers further towards the fence and have the agi drain built in between the retainer and concrete. So that the water from the concrete and subsurface water from the lot behind will be drained.

I also intend to have plants in containers along the fence. What is the best way to tackle this?

Thanks in advance.

[EricL]

Hello @lijithwv 

I was originally going to suggest installing a French drain, but the issue with that is it might soften the soil of the fence and will affect your timber posts foundation. Instead, I suggest installing an Everhard 3m EasyDRAIN Polymer Grate And Prejoined Channel right up to the edge of your concrete walkway. This will catch the water coming from your side. As for the water coming from the fence, I propose covering the soil with concrete and creating a slope that links right up to the neighbour's fence sleepers. 

Any water coming from their side will be guided by the concrete towards the drain channel. It's important that the concrete have a waterproof surface so that none of the rainwater goes down below it. The best part is that you can still put potted plants in that area.

Let me call on our experienced members @Dave-1 and @Nailbag for their recommendations.

If you need further assistance, please let us know.

Eric

[Dave-1]

Good Evening @lijithwv

The soil looks brand new as in it has no flow lines yet? Have you seen water come across from the high side of the fence yet?

If you hose the driveway, in which way does the water flow down the driveway, middle, to a side?

I like your idea of a socked ag pipe burried with say white bebbles along the side of your driveway with a sleeper edged garden bed behind it. It depends on the amount of water you have comeing down from the fenceline and off your driveway. If its a large amount then I would suggest to step up to the next level with @EricL 's Everhard drain. I have just installed three meters between my gabion wall, pavers and a concrete slab to take care of excessive inundation compared to just a rain event.

Oh I prefer 100mm socked pipe, if you are going to do a job of digging a trench then why not use a bigger pipe, less prone to filling up

Dave

[lijithwv]

Thanks @EricL and @Dave-1 for your response.

The soil looks brand new because we just finished concreting this section couple of weeks ago and so I haven't actually seen how much rain water will be coming from the lot behind the fence. Regarding the water from our concrete, it is sloped away from the house so water flows down into the 600mm section of clay soil. We have a drain point at the left end of the concrete (as the slope is from right to left) which I am planning to connect the agi pipe into. I don't expect to have excessive inundation but just want to manage rain water runoff from the concrete and from the lot behind.

I am leaning towards the idea of having a socked agi pipe buried with gravel along the side of the concrete with a sleeper edged garden bed behind it. What will be the best way to cover up the garden bed though given it will have a slope from the fence to the sleeper edge? or will it be any better to completely remove the sleeper edge and just have the agi pipe near the concrete and fill the entire section with gravel/pebbles?

[Dave-1]

Afternoon @lijithwv 

Either a garden bed behind the sleeper or have it sloped with pebbles, If its a slope you go for then I would suggest a shallow slope so it retains the pebbles. You could always go

-Driveway edge

-socked ag pipe

-Pebbles to cover the pipe

-Sleeper burried to give edge to sloped area

then cover the sloped area with pebbles. The edge will stop them cascading onto the driveway.

Both garen bed or sloped area with pebbles work. depends on personal preference and also how much maintenance of the area you want

Dave

[EricL]

Hi @lijithwv 

I've done a quick render of your sleeper garden, please have a look and tell me what you think. The sleepers have been buried down to 100mm and the ends covered up.

Please let me know if you wish to move things around, I'm more than happy to redraw the sleepers for you.

Eric

 

[lijithwv]

Thanks @Dave-1 

Looks like this is the way to go.

Also, I would like to lay 2 sections of weed mat or permeable drainage mat. 1 - under the agi drain section and 2 - under the pebbles in sloped area. What will be more suitable for my use case - weed mat or permeable drainage mat? I assume permeable one under the agi drain and just weed mat under the pebbles. What is the best way to attach either of them on to the concrete end?

For the pebbles on the slope, is there any product recommendations that I can use to hold them in place at the higher end?

[EricL]

Hello @lijithwv 

I propose using Everhard 600mm x 6m Drain Matting or Geotextile instead. These are designed to work underground and last much longer than ordinary weed mat. In regards to holding the pebbles on a slope, there is currently no product that can hold the pebbles in a permanent sloped position.

If you need further assistance, please let me know.

Eric

[lijithwv]

Thanks @EricL for the render and the drainage mat suggestion.

With the rendered plan, only problem is that I wont be able to build a full rectangle garden bed as shown in the render as there will be fence footing in between where the back sleepers will go, so it has to be either U shaped or just the front sleepers. Also I was planning to use a single sleeper high retainer with a sloped garden bed. 

Btw what software do you use for these renders if you dont mind me asking. 

[EricL]

Hi @lijithwv 

I use Sketchup for all my renders. If you are using the full height of the sleeper, I suggest buying another length of sleeper and cutting it down to be used as feet or posts for the other one. 

I suggest having a quick look at this guide - How To Build Retaining Wall. Even if it is a single level, you'll still need proper footing to prevent it from leaning over.

If you need further assistance, please let us know.

Eric