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Water- part one

January 14, 2009

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!

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2 Comments leave one →
  1. January 15, 2009 12:54 pm

    This is very useful information. Thanks for the post…

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