Dealing with water in the landscape:
So, we’ve successfully moved the water away from the house and into the landscape. Now what? To figure out the best course of action, we need to answer some questions.
- Is my soil sandy, loamy, or clay?
- Will the water flow over pavement or planted areas?
- If planted areas, are they turf? Groundcover? Mulch beds?
- If paved, is the pavement pervious or impervious?
- Are there any features that would also be negatively impacted by water?
The best way to determine the makeup of your soil is to have a soil test done. Clay soils become saturated very quickly, and once they do water will stay on the surface. Sandy soils drain very quickly, but you don’t find them very often in our part of Virginia. Loamy soils have high concentrations of organic matter, which is great because they can absorb more water, and will slowly release it as plants needed. This is why during drought conditions, plants in well-conditioned soil will do far better and with less water than plants in poor soil.
The rate that water is re-absorbed can also depend on what is covering the surface. There’s a growing anti-lawn movement in the gardening community, but healthy turfgrass can be a great “sponge” for absorbing stormwater. Groundcovers can also fulfill this need. However, if you have large mulchbeds with only a few plants, you won’t get the same benefit. In fact, you may end up with problems from mulch washing out of the beds in severe storms. As one of my nursery guys says, “mulch is not a groundcover.”
Paved surfaces are a whole other issue. Standard concrete and asphalt will not allow water to penetrate, so the water sheets off the pavement and increases the load on the next permeable surface. Obviously, stone or brick patios set on concrete will do the same thing. A lot of folks mistakenly believe that pavers allow water to penetrate, but this is not true for standard paver installations. The reason for this is that standard practice is to use polymeric sand for the joints. This assists in locking the pavers together and preventing weeds as well as loss of joint sand, but it also causes the pavers to shed water just like a poured slab. Additionally, pavers are installed on a compacted base of what is called crusher run- essentially a mix of large and small aggregate that is mechanically compacted. Very little water would get through this layer.
Paver manufacturers have since come out with pavers that are specifically designed to allow water to pass through larger joints, through the bedding layer, and into the soil. Rather than a tightly compacted, closed bedding layer, the pavers sit on a layer of uniformly-sized large aggregate (typically 3/4″ clean gravel) that allows water to pass through easily. Some of the more readily available manufacturers of pavers in Virginia are EP Henry, Techo-Bloc, CST, Belgard, Nicolock, and Rinox. Unilock also has several options under their Eco-Paver line, but Unilock seems to be just starting to move into our area. It’s a nice looking product, but any time you’re dealing with a paver product- be sure you can get it before you plan a space around it.
It’s also important to consider any other areas in your landscape that could be affected by water. For example, you’ll want to make sure that stormwater won’t be directed into a swimming pool or water feature, as that could drastically impact water quality. Consider your plant beds as well. I have a swath of plant bed that’s just downhill from a drainpipe outlet, and very little will grow there. If I don’t re-route the drainline, I’ll likely end up with an iris garden in that spot.
An excellent way to deal with stormwater and assist with groundwater recharge is to create a rain garden. To do so, you excavate the area to create a basin of sorts, amend the soil to allow water to drain freely, and plant things that will tolerate and even enjoy “wet feet.” Rain gardens can be a beautiful and functional solution to stormwater concerns.