How can we improve drainage & prevent a bog (photos)
SandT
Posts: 70
We managed to level our garden which was previously covered in slate chippings.
But after recent rain, I can see that the clay soil is pooling water. How would you advise improving drainage today, before we arrange for topsoil and turf in the spring? Do we need to dig a trench and lay a French drain? If so, I would be very grateful if you can guide us through how to do this.
It's a 25 foot garden that faces NNE. thanks! Sorry, no idea why the photo keeps posting upside down.
Last edited: 28 January 2017 13:13:43
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Hi there
I can't help much with improving the soil but if you do end up putting in a french drain where do you plan on running it to? You have houses on three sides so you can't run it out those three ways. I don't know if you can run it into your drains some way without getting into trouble with the council.
All I can offer is make sure you don't end up like a neighbour of ours who as a result of ill considered drainage now have nowhere to drain to. Work out where you can drain to that is acceptable by the community and work back. Tip for the day- don't flood your neighbour!
That's right, we are in a skinny terraced house.
Our builder is going to put in channel drains along the patio which is just in front of this photo. The channel drains then soak to the regular drain I presume?
This is Zone 2 London so we can't drain out to a stream, storm drain or anything like that.
I would appreciate additional peoples' views on whether a French drain is too far. What if we just mixed some coarse gravel or sharp sand into the soil for example? I read somewhere that adding topsoil before your lawn will create a sponge effect. It's hard to know what to believe.
Last edited: 28 January 2017 19:56:11
SandT, do your neighbours have drainage problems in their gardens? If they don't, it could be just that your garden area is quite compacted. Did you use machinery to level it? If so, I'd say compaction is almost certainly the problem.
The soil in photo 2 looks nice and dark, not particularly full of clay, which is promising - and not waterlogged over much of its area. If it's been covered in chippings the soil may well be lacking in organic matter in addition to being compacted. Organic matter acts as a sponge, holding water in the structure of the soil instead of allowing it to "puddle"; you don't want to add a lot of organic matter before turfing or seeding a lawn, though it's a really good idea on borders, but I can't see why adding topsoil should be a bad idea. After all, topsoil is what is already in your garden...
You can dig in pea gravel to assist drainage, but not coarse gravel, which would work its way through your lawn. Once you have an established lawn you can spike it and top-dress with sharp sand to help drainage through the turf.
I suspect Clueless is right, and you're not allowed to drain your garden into the council's drainage network - and certainly not into your neighbours' gardens. But hopefully you'll find it's unnecessary to go to those lengths.
It is quite important to find out where the waterlogging is coming from before you decide how to manage it. Are you at the bottom of a hill or do you have natural springs or a water source draining into your garden? Is the water-table high? Do you have drainpipes in your property or your neighbours' that vent onto your garden? Dig a hole about 2 feet deep and leave it for several hours. If it has water in when you return, and how much water, will tell you a lot about the problem.
The reason for these investigations is that if the water is more than just rain and heavy soil you will not improve it with a bit of grit and some top soil and your builder may not have the expertise to deal with it. The slate chippings may have been a sort of solution. Talking to neighbours about their soil may bring further information, too. Depending on what you find out, you may need to consult an expert, especially with the issues already mentioned about where you can drain the water to. No one else will want it. Good luck!
Hi Posy
There are no natural springs, we are not at the bottom of the hill, and no neighbours' water is draining into ours. I can only assume that as we are in central London, the water table is high. I will dig the 2 foot hole today and test it.
I really don't want to spend a lot of money on correcting this. We both have busy full-time jobs, but would just love a lawn in the spring. I wish there was a medium – effort solution! Thanks all.
Hi
There are no natural springs, we are not at the bottom of the hill, and no neighbours' water is draining into ours. I can only assume that as we are in central London, the water table is high. We dug a two foot hole and it does fill with water and didn't drain well.
What if we created French ditches, I.e. dig a T-shaped ditch and fill it with pea or coarse gravel? There is so much conflicting advice around! Thank you and happy Sundays.
Hi SandT. I can understand very well that you don't want to spend a fortune on this: it all adds up so quickly. I know enough to appreciate your problem but not enough to solve it because it is not so much a gardening issue as an engineering one. You do need knowledgeable advice because draining land is complex and there are issues about where the water goes, too. Someone on this site will know how to find out about your problem. I wish you all the best and hope it goes well and inexpensively.
** Update **
Okay, sorry for the multiple posts. I don't know how to delete an erroneous post.
Here is a picture of the 40cm hole after the water had drained away. (Again, the picture always rotates itself sorry). The yellow layer appears to be sand – presumably from the previous owner's hard landscaping maybe? The soil at this depth is definitely clay, but not gloopy sticky stuff. When I tried to roll it into ball it wouldn't retain its shape. Good news I hope but advice on improving the drainage at the bottom is still much appreciated!
thanks
It could be that your soil is simply compacted and that's causing surface water to be slow to drain. Your soil doesn't look like particularly bad stuff to me. Rotovating it, especially if you add grit etc. will improve drainage and perhaps enough for your needs. Mixing in mushroom compost would also help with the soil structure and the lime helps break down clay. If it doesn't work, you have still improved your soil. Hard work but not too expensive to try. Alternatively, consider building raised beds around some or all of the perimeter and fill with those with soil extracted from the centre. You could then lay a thick layer of hardcore or gravel for lawn drainage and cover with 15cm of topsoil to lay the turf on.
I know people who would kill for that soil, Bob is correct it has been compacted by the slate or whatever it was topped with. You cannot do very much before Spring and that hole looks dry to me if it was high water table it would have water in it so leave the hole for now and keep checking it until the weather warms up enough to do some serious work. A perfect lawn is built up in layers of hardcore for drainage then six inches with plenty of grit, ten inches of topsoil then seeded. That of course after raking in some washed sand and doing the gardeners soft shoe shuffle to create a pan for the seed.
A quicker and cheaper method is keep an eye on that hole for a while see what happens in heavy rain then do what I did, dig a sump at one end lay in rubble, old broken brick and gravel about 18 inches to 24 inches deep then fill in with soil. I double dug my patch although a hired rotavator would do a reasonable job, rake and level then compact it with your feet (gardeners shuffle) buy and roll out a medium turf plenty of GC's or Nurseries sell good quality turf rolls then water it every day for a couple of weeks and that means water it well, use a sprinkler ten minutes with a hose is not enough. You should have a manageable lawn you can sit out on in no time. This is of course my opinion after years of lawns plus helping maintain a bowling green, it is up to you although the more work you put into it the less you need do later.
Frank.