The best way to divert runoff water away from your driveway is to install a French drain or swale. This drain will intercept the water that runs toward your driveway and channel it downhill. With a well-constructed drain, you can stop your driveway from being flooded with runoff.
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7 Steps to Stop Driveway Flooding with a New Drain
Constructing a drainage trench is the least expensive and most effective way of preventing water runoff from flooding your driveway. Other options, such as building berms or replacing your driveway with water-pervious pavers are more labor-intensive and don’t work as well. For this job you will need:
- Pickaxe or mattock
- Landscape gravel
- Landscape fabric (optional)
- Perforated drain pipe (optional)
If you’d like to try some tools that can make the job easier, consider using some specialized trenching equipment. The right tools make a job much easier.
Swale or French Drain?
The first decision you need to make is whether you’ll be installing a swale trench or a French drain on your property. A swale is simply a trench with gently sloped sides. It is open, usually with a layer of gravel at the bottom and water-loving plants growing alongside it. A French drain is a trench with a perforated pipe surrounded by gravel. It is then topped up with gravel until it is level with the surrounding ground.
- A swale is an open trench with sloping sides and a gravel-lined bottom.
- A French drain is a trench that contains a perforated drainpipe buried in gravel.
- Swales collect water and slowly allow it to percolate into the soil, where it feeds water-loving plants.
- French drains collect runoff water and carry it away to a dry well or end spout.
A swale requires less time and materials to build, but it will not drain away water as efficiently as a French drain. If you have severe driveway runoff, install a French drain.
Determine Where Your Drain Should Be
Where is the runoff water that floods your driveway coming from? Typically, runoff comes from a slope or point that is higher than your driveway. This can be at the top, bottom, or side of your driveway—it may even be from a point on your neighbor’s property. Wherever the water is coming from, plan to dig your trench like a wall to intercept the water and divert it downhill.
- Find where water runoff comes from. If necessary, use a hose to wet the area near your driveway and observe where floodwater begins to run onto your driveway.
- Runoff may come from more than one point. A low driveway may receive runoff from both sides. This will require two drains to control the water.
- Place your drain so that it intercepts the flow of water.
- Your drain should run downhill to divert water. It may need to bend to both intercept water and maintain an adequate slope.
An improperly sloped drain won’t direct water downhill. The good news is, only a gentle slope is required for proper drainage. As long as the trench slopes downhill at a rate of 1 inch (2.5 cm) over 10 feet, it will drain. To make certain your planned trench will drain properly, find your yard’s slope.
Dig Your Trench
Once you’ve decided what style of drain you want and where it will be placed, it’s time to dig your trench. This process is simple, but it can be tough work. To get the job done right, follow these steps:
- Mark the path of the drain with this marking paint.
- The ideal trench depth is 18 inches (45 cm).
- The ideal trench width is 9 inches (23 cm).
- When creating a swale, dig to a width of 18–24 inches (45–60 cm) so the sides slope gently down.
- When building a French drain, leave sheer sides with little to no slope.
The right trenching tools will make this job easier, as will moist ground. If the area is currently dry, water the ground for 1–2 hours the day before you dig your trench. This will make the soil easier to excavate.
Line With Gravel
Both swales and French drains require a layer of gravel at the bottom. Make sure to use large gravel, river rocks, or landscape gravel. Larger rocks allow water to percolate and flow, while pea gravel and smaller rocks compact and block runoff water from draining.
- Line the bottom of the drain with 3 inches of large gravel or river rocks.
- When laying gravel in a swale, place gravel only in the central channel, leaving sloped sides bare.
A gravel bottom allows rainwater to percolate into the drain without eroding soil. It’s also essential for French drains to have a gravel bed because a perforated pipe laid directly on the soil will become clogged and nonfunctional.
Construct a French Drain or Swale
Once you’ve got your initial layer of gravel in place, it’s time to finish your drainage trench. If you plan on making a French drain, follow our complete guide to drainage trenches. If you’re planning to construct a swale, the steps are simpler.
- If you are building a swale, plant the sloped sides with grass seed or plants that thrive in wet conditions.
- Lilies, irises, and hibiscus all thrive in the extremely moist ground of drains and swales.
With your drain complete, you now have the means to control and direct rain and stormwater away from your driveway.
Terminate the Drain
Where will all that water drain to once you direct it downhill? It’s critical to make sure you don’t simply shift your runoff problem away from your driveway to another portion of the yard. To control water runoff at the end of your drain:
- Terminate the drain at a dry well—a 3 foot (1 meter) circumference hole approximately 3 feet deep and filled with large gravel.
- End the drain at a water garden or pond feature.
- Alternatively, attach a length of solid, flexible drainpipe to the end of your French drain. Direct the water to a municipal storm drain.
A dry well is typically the most practical solution for terminating a drain. It allows stormwater to filter down through the gravel and disperse belowground. It essentially takes that aboveground runoff and distributes it deep beneath the surface.
Turn Your Drain Into a Lawn Feature
Drains don’t have to be eyesores on your lawn. A swale lined with smooth river stones and planted with irises becomes a natural garden. A French drain topped with gravel and lined with bricks is unobtrusive and attractive.
- Use attractive gravel or river stones to line your swale or French drain.
- Plant your Swale with grass, or water flowers such as lilies and irises.
- Top your French drain with this drain grate.
Not only is your new drain responsible for keeping your driveway dry during even the worst storms, but it can also add to the look of your yard.
How Do You Divert Water Runoff from Your Driveway?
Drains and swales are the best way to stop runoff from pooling in your driveway. They safely direct rain and stormwater away so it doesn’t flood other areas of your yard. A trench or swale is a DIY project that you can tackle, while other options like breaking up a concrete driveway to replace it with water-permeable pavers are expensive and require a lot of heavy labor. Direct water safely away from your driveway with a swale or French drain for the best results.