Any Gardeners or Landscapers on the forum?

[NickBW]

Hi all

I recently levelled my garden and in the last 3 or 4 months of heavy rain, i have noticed some flooding areas on the lawn around the wall i had built.

 

To solve this I plan to rent a trencher to dig the required trench to lay a land drain.

This is my plan to run my perforated drainage pipes, 900mm deep, on a bed of shingle then topped up with shingle, wrapped in geotextile as documented here on Paving Expert
https://www.pavingexpert.com/drain16

 

I am worried if running the pipe across the middle is a good idea or not.   Will it discolour the grass?

 

 

 

[Richard (OldStager)]

I did this in a previous house, pretty much what you are proposing.

As long as you take the turf out carefully it won't cause issues, domestic type grasses are pretty resilient. What I would suggest is to leave the pipe/shingle to settle for a while before covering with soil , this allows the whole thing to settle. May be worth tamping down the shingle too, as long as it does damage the pipes. Once settled place the turf back over.

I did mine all a bit too quick, and ended with dips where the pipes were, which needed further soil over the top to fill them.

Richard.

 

ETA.

I also in the end , had to add a sump pump as although the pipes quickened the drainage it still took far too long to clear ( it was a clay based soil), a bit more work and expense but never had a flooded lawn again after that.

[NickBW]

11 hours ago, OldStager said:

I did this in a previous house, pretty much what you are proposing.

As long as you take the turf out carefully it won't cause issues, domestic type grasses are pretty resilient. What I would suggest is to leave the pipe/shingle to settle for a while before covering with soil , this allows the whole thing to settle. May be worth tamping down the shingle too, as long as it does damage the pipes. Once settled place the turf back over.

I did mine all a bit too quick, and ended with dips where the pipes were, which needed further soil over the top to fill them.

Richard.

 

ETA.

I also in the end , had to add a sump pump as although the pipes quickened the drainage it still took far too long to clear ( it was a clay based soil), a bit more work and expense but never had a flooded lawn again after that.

Thanks for the reply!  Sounds like I am on the right track then. 

[Richard (OldStager)]

You're not alone, a lot of my neighbours have said the last few years that their gardens now flood where once they did not, this isn't an increase in rain fall, but the fact that many properties get rid of the front garden ( to park cars on it) and either concrete over it or pave it. Subsequently the surface water then has no where else to go other than the lawned areas. If it rains for more than a day , even my front garden gets about half an inch in places, and mine is all gravel, nothing sealed at all.

[SootySport]

If you have a clay subsoil, it won’t allow water to drain down deep into the ground. Dig down in the centre of the lawn to find the ballast layer and if it’s not too deep, dig a trench across the lawn or a few squares where the water collects. Fill the trench or squares with coarse shingle or ballast and top off with Top Soil.   Essex is known to have a clay layer sub soil and I have a small garden that flooded in winter. Had the boys round to dig out 1metre in the two lowest parts of my lawn through the clay layer to the ballast layer.  I’ve had no garden flooding since 2006. With a large garden it would be worth hiring a mini digger.  

[dombanks]

the comment about clay is a good one, Back in leicester the drive was a gravel thing which would puddle up a lot. I wanted to level it and install one of those cage soak away things and was told by a few neighbours that we weren't allowed to as the clay would just hold it. might be complete BS but worth checking. 

on a different note my parents have had a cage soakaway under their lawn for over 30 yrs to take their flat roof water and there was never any issue with the grass being a different colour

[Mark Stanton]

Soakaways do not work efficiently (if at all) in strata of low permeability i.e. clay, installing a crate attenuation/soakaway system may simply mean you will be storing water or even attract it, due to creating a void, in clay soils.

 

Crated attenuation/soakaway systems work really well in more granular strata, with a higher permeability.

 

Try not to use shingle in land drains, rounded single size pea gravel is self compacting and provides a better void ratio for the water run-off.

[Rhett Turner - Black Country AO]

Another general thought, Lawns, especially when the contain good high quality and dense grass can act like other hard surfaces and should therefore be treated in a similar way.  ie if this were a block paved, slabbed or decked area what would you do, make sure there is a degree of fall, make sure there is somewhere for the water to run off to etc. You should not have a perfectly flat paved area neither should you have a wall at the lowest end of a run, without a gully or similar.

If it is flat then you may need to regularly aerate the lawn, ie make lots of small holes in the top layer, if fact thinking about the Golf course aerating is something that is done regularly to help with drainage. 

A nice looking garden by the way