Simple Factoids About Landscape Drainage

Last night I signed contracts with some great folks, and they asked me to add some drainage work while the crews are out there. We walked out to look at what was going on, and as usual I was appalled. When their patio was installed, the contractor connected the downspouts on the rear of the house to 4″ corrugated drain pipe. These come together in a “Y”, and then a short piece goes out to a low spot in the yard. Here, the pipe turns straight up and is covered with a grate flush with the lawn.

Hmm. So when it rains, water burbles up out of this contraption and pools at the corner of the screen porch for a couple of days. Plus, all the rainwater at the back of the house is being brought together into a single 4″ pipe. Idiots. So in the interest of breathing some common sense into landscape and drainage design, here are some points to ponder:

  1. Water flows downhill. Elementary, my dear Watson, but often overlooked. Don’t terminate a drainpipe in a flat area if five more feet lets you terminate on a slope. And remember to keep a constant pitch downhill!
  2. Corrugated pipe is fine, but smooth-bore is better. We’re usually gently pitched when running drain lines away from the house, which means the water isn’t moving super fast. That means sediment and funk from the roof can get stuck in the ribs of corrugated pipe and eventually clog. An even bigger issue is that smooth PVC drainpipe is rigid, so it’s easier to keep it pointed downhill. Corrugated pipe will conform to the ground around it, so after settling and a few years of frost there are uphill sections. See point # 1.
  3. 4 + 4 + 4 +4 does not equal 4. All too often I see companies hook 4 or 5 downspouts together into one 4″ pipe. Guess what? That’s a lot of water, and may well be too much for the pipe. If you add water to a funnel faster than it can drain out, what happens? If you want to get an idea of how much water comes off your roof in one storm, there’s a cool rainfall harvest calculator on this page.
  4. Pop-ups are ok, but daylight is better. Pop-up emitters serve a purpose. If you have to end a drain line in the grass, a pop-up emitter keeps you from destroying the line with your mower. It’s also a mechanical system that can fail. If the site allows it, you’re better off ending with the open end of the pipe pointed downhill – what we call “daylighting”.
  5. Be a good neighbor. This one’s pretty huge. Think about where your water is going if you move it to a discharge point out in the yard. If you’re in a subdivision where water moves through the backyards, what does it do to your neighbors if you build raised beds and block that flow? Not only is it rude and crappy, it’s often illegal to alter the drainage in a way that adversely affects your neighbor. Just food for thought.

Drainage doesn’t have to be overly complicated, but it’s definitely worth planning properly. Most residential systems won’t fail this spectacularly, but why risk it?

River birch is a great choice for wet areas!

Principles of Design: Proportion in the Landscape

Proportion and scale are two related design principles. Proportion refers to the size relationship that parts of the design have to each other and to the design as a whole. On a small scale, an example of proportion is the size of a chair’s legs to its back or seat. On a bigger scale, an example of proportion may be the size of a pergola’s posts in relationship to its beam. If the relationship of the parts is pleasing, we consider it to be well-proportioned.

As with many things, the ancient Greeks had this one under control. They referred to a concept known as the golden mean, an imaginary line that divides an object into unequal yet harmonious portions, somewhere between 1/2 and 1/3. It’s easy to see this at work in interior design; think of tiebacks on curtains, or where a chair rail is located.

There’s also the golden section, a mathematical statement of proportions. This uses a progression of numbers – 3, 5, 8, 13, 21, 34… – that relate to one another in a pleasing way. For instance, a patio 5′ wide by 8′ long is considered pleasing. Want it bigger? Multiply both sides by the same number. Using the number 3, that gives us a patio 15′ wide by 24′ long. Theoretically, a room or space created using the golden section should be the easiest to furnish and work with.

Proportion is important in the landscape because we’re dealing with so many large items, and all too often people are afraid to go big. Here are a few examples:

When it comes to pergolas proportion makes a world of difference. Bigger is, quite often, better. Compare the proportions of the pergola that was there (top) to the one we replaced it with (bottom).

This custom arbor I designed is one of my favorite pieces. The house it belongs to is in the 9,000 sq ft range and it sits on 75 acres. The existing arbor was a run-of-the-mill garden center piece of junk that looked like paperclips on a basketball court. This one has the “oomph” to have some presence.

I’ve also talked about picking plants that suit your home and site. Again, proportion is so important! The trick is to find a plant that’s not too big for your lot (especially a smaller city lot) but is big enough to stand up to your house. Not sure? That’s what professional landscape designers (like me!) are for.

Next up: balance!

Principles and Elements of Design: a Series

You may have noticed that it’s winter outside, so there’s not a lot of pretty stuff for me to take pictures of right now. It seems to me it’s a great time to talk about design, and what makes for really good design. Over the next several weeks I’ll talk about the principles and elements of design, and show examples so you can better understand them at work in design. It should be a lot of fun, as I remember when I first learned these in interior design class I had a lot of “aha!” moments.

Principles of Design

The principles of design are abstract concepts at play in good design. They are:

  • Scale
  • Proportion
  • Balance
  • Rhythm
  • Emphasis
  • Harmony

Elements of Design

Where the principles of design are abstract concepts, the elements of design are the actual, quantifiable parts of any design. They’re where the rubber hits the road:

  • Space
  • Shape
  • Form
  • Mass
  • Line
  • Texture
  • Pattern
  • Light
  • Color

Each principle, and each element, will have its own post. It all starts Wednesday, so be sure to check back. If you want to be notified when new posts go live, click here to subscribe to this blog via email and you’ll receive alerts in your inbox.

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.

Cryptomeria Japonica ‘Yoshino’

Cryptomeria japonica 'Yoshino'
Cryptomeria japonica

There’s not a lot going on in the garden today, so I figured I’d snap a picture of my cryptomeria, aka Japaenese Cedar. It’s a fantastic tree: quick-growing, sturdy, and tolerant of a wide range of conditions. This one sits in a soggy part of the yard. I was a little hesitant to put it here because most of the info I’ve read has said that cryptomeria prefers a well-drained soil, which is not something I have much of in our yard. I planted it a little high, graded up to it with soil from my compost heap, and it’s taken off like a shot. I estimate it’s put on a good 18-24″ of growth in its first year. I’m quite curious about what it’ll do when it actually gets established.

I make no secret of the fact that I despise Leyland Cypress as a privacy screen in subdivision settings. Because of its narrow growth habit, you can work a Cryptomeria into a mixed planting screen to great effect. Interplant it with an evergreen with a broad, dark leaf and you’ll have a screen with some textural and color interest. With just a little thought, you can spend the same amount of money as you would on Leylands and have a planting that will just get richer as it matures.