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Gardening on a slope...Ground water issues.

lesinnllesinnl Posts: 43
in Garden design
Hi good morning all.  I live on a dijk; sand at the top, clay at the bottom of the garden. I want to remodel this area of my garden that is not the lowest part of the garden but is very much affected by ground water.   From top to bottom the drop to this point is 2metre 10cm. Behind me I have a drainage put, which is currently not attracting any of the ground water that comes up over the boarder and over the tiles. As in the photo.  The benefit of this area is that I use the ground water in sumer to water the garden, however I do need to lay new tiles and need to manage the water and future proof this area against rising ground water that is currently about 30cm above the level of the tiles. I cannot raise the tile level. Any ideas you wonderful lot?

Regards Les
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  • Lizzie27Lizzie27 Posts: 12,494
    @lesinnl, I'm so sorry, that sounds far too complicated for me to understand.

    Do you live in Holland on a dyke where the water is higher than your garden and therefore it is seeping through at the bottom? Is it worse now than in previous years?
    How do you access the groundwater to water your garden in the summer?

    Sorry for all the questions! More photos of your garden would help us to better understand your problem.
    North East Somerset - Clay soil over limestone
  • FellsmanFellsman Posts: 15
    I'm also struggling to visualize the plot. Would your artistic skills extend to a hand-drawn, rough sketch showing a vertical cross-section (slice) through the garden along the slope (i.e. top to bottom)? If you could add what you think is below ground (as far as you know or guess) that would help too. E.g. if the clay actually extends under the whole plot (even if it is mostly buried) that will make a big difference. Showing what is beyond the garden top & bottom will help as well.
  • FellsmanFellsman Posts: 15
    Google returned this page which has a cartoon section through a dyke. Are you basically saying your garden is the on one of the slopes shown?

    https://www.angloinfo.com/blogs/netherlands/south-holland/hollywood-2-holland/how-dikes-work-to-keep-holland-from-flooding/
  • lesinnllesinnl Posts: 43
    edited October 2023
    Thank you both for taking on this puzzle....I have attached one more photo so you get a better aspect of the situation.  I live indeed, as indicated on your image Fellsman.  "Officially" we are not below the water table, eventhough the water table has been raised by 1M in the past year. The red line indicates the level of my neighbours garden.  You can see that there is "pressure" on the lower part of my garden. I am not allowed to remove excess water into the drainage system, but you see that only in October there is already standing water.  I want to plant a couple of almond trees in the newly grassed area more grapes along the back fence and along the front,  a line of something decidious that can take hot summer sun, yet cope with wet feet in winter. I want to lay new tiles then where you see them now. I have found a potential solution; a product that soaks up the water, holds it then releases it slowly over time, it say it acts as a buffer. Thanks for showing your interest.
  • DovefromaboveDovefromabove Posts: 88,147
    edited October 2023
    Sounds as if that might be useful in Suffolk at the moment 
    😢   

    Hope it works for you 🤞 

    Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.





  • LoxleyLoxley Posts: 5,698
    The water appears passing down through the terraces you have made, but when it gets to the bottom one the board and path are acting as a dam; water cannot get past so it goes over. So, you should lay a perforated pipe drain in the soil behind the 'dam', and then connect it to the drain behind you - or a lower part of the garden - via a trench under the path. The perforated pipe should be surrounded by free draining granular material e.g.pea shingle, and permeable geotextile.
    "What is hateful to you, do not do to your neighbour". 
  • LoxleyLoxley Posts: 5,698
    edited October 2023
    Alternatively you could make the lowest terrace a bit higher and ensure that there are weep holes right at the bottom. Fill the planting bed with free draining soil - I would mix half and half topsoil and sharp sand or grit. The plants will then be sitting with their roots well out of the wet zone, but will be able to get their roots down into it during dry spells.
    "What is hateful to you, do not do to your neighbour". 
  • lesinnllesinnl Posts: 43
    Loxley said:
    The water appears passing down through the terraces you have made, but when it gets to the bottom one the board and path are acting as a dam; water cannot get past so it goes over. So, you should lay a perforated pipe drain in the soil behind the 'dam', and then connect it to the drain behind you - or a lower part of the garden - via a trench under the path. The perforated pipe should be surrounded by free draining granular material e.g.pea shingle, and permeable geotextile.

    Thank you Loxly, is this procedure a "french drain?" I think a combination of solutions from both of your posts should indeed go some way to solving the problem.  I am not supposed to utilise drainage systems for ground water removal but I have no option I feel.  Thank you, now I have my winter project.
  • Lizzie27Lizzie27 Posts: 12,494
    Glad you have got that sorted @lesinnl, good luck with your project.
    North East Somerset - Clay soil over limestone
  • FellsmanFellsman Posts: 15
    It is indeed a French drain although i think the originals did not have the pipe, just rubble fill. There are other names (e.g. land drain) for basically the same system. To work properly it will need to be a certain depth below the surface (30cm minimum? to be any use at all, but probably more). Remember you can never drain the water below the depth of the bottom of the pipe (at best). Below that it will remain waterlogged if it is solid clay. At the same time the exit of the pipe needs to be above the local water table at the exit point.(and remember you need a 'fall' or slope on the pipe ~1in50). That means you need a discharge point where the natural water level is say 50cm-ish below the level of your tiles. Its not obvious you have (or can access) such a location.
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