Date:12 June 2012
Q Our house is at the base of a hill, and every rainy season we get ferocious run-off that damages flowerbeds and undercuts the driveway shoulder. The hill is not on our property, so we can control the run-off only once it reaches the yard. Every year I repair the damage, and every year it happens again. What’s a permanent fix?
A Run-off frustrates many homeowners and the dirt, wood chips, grass clippings, and debris it scours from the yard can pollute public waters. So we’ve got two goals here: divert the water to stop the damage to your property, and slow it down enough so that it percolates into the soil, rather than racing over it.
All of the following approaches will work well, depending on the situation.
Build a berm, a small hill covered with grass or other plants that will divert run-off around what you want to protect. You’ll need to think about where the diverted water will flow and then consider what to plant. Grass is easy, until it’s time to mow it. A variety of other plantings might be easier to maintain and can help the berm blend into the landscape. The best brief guide I’ve seen is Building Soil Berms, available online from the University of Minnesota. If you’re looking for a reasonably quick fix to protect plantings and structures, a berm may be the best option.
Intercept the water by using a swale, a shallow ditch with gently sloping sides. You can also use a French drain, a gravel-filled trench that may have a perforated pipe at the bottom. New products include the EZ-Drain, which consists of a perforated pipe and plastic beads encased in a tube of landscape fabric. The fabric surrounds the pipe like a sock and prevents dirt from infiltrating and filling up the pipe or the air spaces between the beads. Because French drains handle water that is moving not just over the soil but through it, they’re the best solution for keeping water out of a basement.
Route the water into a dry well. As the name suggests, this is a hole in the ground that remains dry most of the time. However, when water is flowing, it can be routed to the well by a swale or roof downspout. Dry wells are particularly helpful in a spot where downspouts are flooding a large paved area or when you’re coping with run-off from a large roof. Finally, you can dig a dry well in any low area where a big puddle tends to form.
Grade broad surfaces to direct run-off away from houses, sheds, outbuildings, and patios. In most cases this requires a professional excavator or expensive rental equipment. But it’s almost always an essential step for correcting a flooded basement or crawlspace.
Replace impermeable surfaces such as concrete with permeable pavers and gravel. This can be expensive, but it’s worth considering, especially if you’re already replacing deteriorated asphalt or concrete.
A final word of advice is in order before you start swinging a pickaxe or hiring a Bobcat loader. Depending on what part of the country you’re in, it may be subject to specific rules about landscape modifications that affect groundwater, even on a small scale. These regulations are more likely to apply if your house is close to a lake, stream, or seashore, but it pays to check requirements no matter where you live. It’s also smart to check with utilities in your area about your intent to dig. It may be useful to know the location of buried utilities, such as telecom cables, water lines and sewers.