If you suffer from the gardener’s nightmare of an unlandscaped sloped yard, never fear: You can tame the beast with retaining walls. While they are simple to install, however, you must be careful to allow proper drainage, as a buildup of water can be both destabilizing and potentially dangerous. Holes in retaining walls are just one of the ways water pressure can be released.
Retaining Walls Explained
Usually constructed from pavers, concrete blocks or other solid, stackable materials, retaining walls create a barrier against which soil rests, turning a sloped yard into one or a series of flat surfaces. This makes gardening much more feasible than trying to do it on an erosion-prone slope. Because retaining walls keep soil in, however, they also tend to trap moisture. If you do not find a way to release this buildup of water, you could create an unstable situation by allowing water to undermine your foundations or break down the stones used to build the wall.
Because of the danger of allowing water to accumulate, most retaining walls have built-in drainage mechanisms. Sometimes this means a pipe running through the wall from the soil to the other side, called a “weep hole.” It could also be a burlap bag filled with pea gravel, slotted into the stone to provide an escape route for water, though this is an outdated method. Industrial retaining walls leading to drainage ditches always contain weep holes right at the base of the wall, while those in homes sometimes use other methods.
Other Drainage Methods
Retaining wall drainage technology has improved over the years. These days, many people choose to build their retaining walls with a layer of sand packed up against the stones to create a buffer between the soil and wall. Gravel also works, though anything coarser than the soil in your garden puts the drainage layer at risk for clogging and failing. Advanced drainage wall fabrics use light composites to allow for proper drainage in a very thin layer.
The Role of Placement
People often install retaining walls to hold back slopes that ordinarily would slide down due to angle and erosion. Because a lot of erosion occurs due to rain running over the surface of soil, you can reduce water runoff by planting groundcover and surface-rooting plants that anchor soil and use moisture. If, however, you still have plenty of water that moves down the slope, you will need to ensure you give it ample draining room. In this case, you might want to ensure the stability of your wall with some double measures, such as a sand barrier and drainage holes.
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