Water- Part 3

Dealing with water where it leaves the property

In Virginia, I’ve seen a few different scenarios for how water exits a property. In a lot of subdivisions, everyone’s backyard pitches into a swale that carries stormwater into a storm drain. Even if the swale is on your property, you’re usually prohibited from altering the grading such that it impedes the flow of water into the storm drain. I’ve had well-meaning clients who wanted to channel everyone else’s runoff onto their lots and create a giant rain garden. On a larger property you might be able to pull this off, but in a typical subdivision lot you may cause a lot of problems for yourself and your neighbors.

In my situation, I live in downtown Culpeper. A portion of my stormwater runoff ends up in the street and flows into the storm sewer. As this water rushes down the street it picks up oil residues and other contaminants, which will strain the wastewater treatment plant. For this reason, our best course of action is to try and catch as much water as we can reasonably use, and slow the flow of the remainder so that it can more easily percolate back into the ground.

I’ve even dealt with an unfortunate situation where all the water from two neighborhoods ended up in my clients’ backyard- they just happened to be the low point in the area. In that situation, there wasn’t a lot we could do except to make certain the land was graded away from the house, and try to reclaim enough of the backyard to make it usable. As tempting as it may be, solving your water woes by pushing the water into your neighbors’ yards is not an option! Be very careful any time you change the grading and drainage patterns of your lot. If you create water problems for someone downstream, it will be your responsibility to fix them.

The important point here is that for decades, we’ve treated stormwater as more of a liability than an asset. Having made it through a particularly tough drought two years ago, I think we have a better appreciation of the importance- and occasional scarcity- of water. Paying attention to how water enters and exits our properties can help us make the best use of it and ensure there’s enough to go around.

Water- Part Two

Estimated reading time: 4 minutes

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.

Water- part one

Ah, water. We cry out for you when you’re in short supply, and curse you when you won’t go away. But without you we’re nothing.

Water’s a huge issue in the landscape as well. Traditional stormwater management, at least in the landscape field, has been simple: get water off the property as fast as possible and it’s no longer our problem. Attitudes have changed as more gardeners are trying to use rainwater for irrigation, and we recognize the importance of allowing water to recharge aquifers. When I create a landscape master plan that responds to Virginia’s soils and climates, I address water in the following ways:

  1. Deal with water at the house
  2. Deal with water on the property
  3. Deal with water where it exits the property

Each step deserves its own post. I may as well deal with them in order, as this is how I address them in plan.

Dealing With Water at the House:

It’s amazing how much water falls on our roofs in a storm. According to www.gardeners.com, a light rain on a mere half inch can yield 300 gallons of water on a 1,000 square foot roof. For most homes, this water is collected in gutters, travels down the downspouts, and is deposited right along the foundation- exactly where we don’t want it. Rain barrels are a great way to collect some of this water for use in the landscape, but you can see from the above figure that one or two rainbarrels can’t possibly hold all the water from even a small storm. A properly constructed rain barrel includes an overflow spout. All too often, the overflow goes into a hose that trails along the ground- right where the downspout would empty! So less water is being dumped at your foundation, but it’s still not an ideal solution.

What I prefer to do is run the overflow (or the downspout, in cases where there are no rainbarrels in use) into buried drainpipe that deposits the water downhill and farther out in the yard. We call these pipes “daylighted”: the pipe travels underground and emerges at the end, so the water flows out onto the surface of the ground. This only works if you have a point in your yard that is downhill from your home, but it is the simplest (and therefore the least likely to fail) way to deal with water from your gutters.

There are two commonly used types of pipe for this application. The first is corrugated 4 inch black plastic pipe. It’s the flexible pipe that is sold in big rolls, that is you may have seen used as the legs on hay bale spiders. That is a much better application for this pipe than diverting water. Because it’s flexible it can move with frost heaves, which means there may be sections that no longer flow downhill. Also, the corrugation provides pockets that can trap sediment, pollen, bits of leaves, and all the other funk that can get washed off your roof. Eventually, if enough trash builds up, you can end up with a clogged pipe. The pipe also crushes far too easily for my comfort level. A zero-turn lawn mower can weigh as much as 1,600 pounds- something to think about.

For that reason, I prefer to use 4″ PVC sewer and drain pipe. It’s the white pipe that’s sold in straight 10′ sections at home improvement centers and plumbing supply yards. Water and any debris will just rocket through the smooth walls of the pipe, and it has a crush strength of 3,000 pounds. The best part, in my mind, is that I can install cleanouts at junctions or bends on long runs. If there’s ever a clog, it’s easy enough to open the cleanout and run a snake through the pipe. Properly constructed, you shouldn’t have  any problems with this sort of drain system. Mine has been in place for three years with no issues at all. Living in an old house, I need all the peace of mind I can get.

Once the water’s away from the house, what do we do with it? I’ll discuss that in part two!