In order to maximize the amount of play space in our backyard, we recently had many yards of soil brought in. We live on a slope. Our neighbors home behind our backyard is about 3 feet below our property, separated by an old retaining wall.

More recent picture with soil delivered:

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Prior to soil delivery, you can see the property line (fence) and neighbors home behind ours:

enter image description here

We are planning on shaping the soil, and then installing sod on top of all of it.

Previously, we had some large rhododendrons growing on that slope, but both the top and bottom tiers were pretty bare, with clay soil showing.

We’ve never heard about any issues with water running off of our property into our neighbors’ yards. Our neighbors are concerned about water runoff from this new soil hill (slope). They want to come by in a few days to see how the project is progressing.

I have been thinking, since we have the same surface area as before, plus this soil is more absorbent than the clay soil far below it, plus we’ll have healthy sod covering it, we shouldn’t have any water run off issues. Please let us know your opinion. Should we install a French drain near the edge of our property? If so, where should the water exit from it?

Thank you

  • It depends on how much it rains on your region. On my region I would also be worried, but not about water, but because of soil which could slide down. There is also a wall under your new soil: is it capable to take additional weight? [wet soil] Has it drainages? New soil could bury them too low to be effective. As you see, there are many questions before we could answer. But I think you should ask local constructors: they know better climates and soil. Note: you assumptions are wrong: flat surface helps slowing water, and so getting absorbed more Aug 26, 2020 at 8:16
  • I too would be more concerned about soil erosion and it ending up on the neighbour's property. Those rhododendrons you removed will have had root systems, and large root systems stop soil from sliding or eroding in a way that turf will not. You really need to consult a landscape architect; overflow of water, if it happened, would be a problem for your neighbours, but soil or a landslip cascading onto their property would be even worse....
    – Bamboo
    Aug 26, 2020 at 9:11
  • Your neighbors are right to be worried. I've seen runoff issues with a slope much less severe than the one you're creating (turf-covered, BTW); I've also seen "slip" at grades of 25%, which you may be approaching with the new soil. Does your municipality require permits for this type of landscape change? Most don't, but some do and if yours does, you will not be in compliance - which means that the municipality could force you to undo all of your work. I get the sense that you're not using a contractor. If this is true, then get one ASAP.
    – Jurp
    Aug 26, 2020 at 13:27


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