The Proper Drainage Solution for a Sloped Yard

Any yard with a steep topography can present a drainage nightmare. When the slope of a yard goes beyond 4 or 5% you start dealing with issues like runoff erosion and hydrostatic pressure situations. Specifically, since water runs downhill, whatever part of the yard is at the low spot will always end up saturated after a storm, and sometimes long after or even all the time, depending on the water table.

A water table refers to the depth at which groundwater sits constantly. This will go up or down based on how much rain has been in the area recently, but in general it will stay at whatever level it is normally for that time of year. If your water table is 5ft down, if you were to dig a hole that is 6ft down, you would notice a foot of water sitting at the bottom of that hole.

Another way of looking at and understanding a water table is this: Let’s say your water table is 10ft down, but you’re on the side of a hill that is 12ft tall – what this would mean is that you would likely be sitting on a spring where water is coming out of the grown continuously. The steeper the hill, the greater the chance that you could deal with ground water appearing on the surface. Remember also that the water table rises after a storm, and so if you are on the side of a steep hill, you could be temporarily exposed to excessively saturated soil that lasts much longer at the low spot than in other areas of your yard or neighborhood.

When your entire yard is sloped, and your home is built on the side of that hill, this is where real issues can arise, issues like hydrostatic pressure which can cause heaving and sinking due to the unstable soil moisture levels. Besides simply dealing with the headache of a soggy lawn, you could find yourself facing severe damage to the foundation of your home, if these water levels (and the high water table) are not addressed and factored into your structural design. It is not uncommon for home builders to simply grade the yard in order to push surface water around a home, but fail to address the constant presence of groundwater, which cannot be fixed with simple grading.

While a French drain is much more expensive than moving dirt around to regrade a yard, it is the only solution currently known to fix a groundwater problem. If you have a sloped yard and consequently a low spot (or worse, if that low spot is at or near your home), the solution is a French drain. When installed at the low spot, drainage of this sort is designed to interrupt the flow of the water table, helping to maintain a better moisture balance for the yard and adjacent structures. Whether you own a home, are buying a home or building a home, consider whether your property dictates that you need drainage, in order to ensure the longevity of your home and foundation.