To construct a rock drainage ditch, it’s essential to plan a trench path that captures water and conducts it downhill. Then, dig your trench 18 inches deep (45 cm) and 36 inches wide (90 cm). Line the trench with landscape fabric, add 8–10 inches (20–25 cm) of gravel, and top the gravel with rocks or smooth stones. Finally, add a border of stones or plants to turn the trench into an attractive dry creek bed lawn feature.
7 Steps For Building a Rock Drainage Ditch
Building a rock trench for drainage is a simple and effective way to stop water from running down a hill or to draw standing water away from boggy areas and drain it away below ground. Your rock drainage trench can be a simple, straight-line of uniform width, or you can construct it with natural bends and wider areas to create the look of a dry creek bed. Here’s how to build your drainage trench:
Gather Tools and Materials
In order to dig and construct a rock drainage ditch, you will need the right tools for trench digging. You’ll also require the materials to line the ditch. At a minimum, you will need the following:
- Pickaxe or mattock
- Water permeable landscape fabric
- #3 crushed stone or 3/4 inch gravel
- Fieldstones, large rocks, or river stones
Optionally, you can also consider adding water-loving plants, such as irises or lilies alongside your drainage trench, to turn the trench into a garden element.
Plan the Ditch
Your drainage system will work best when it is positioned so that water traveling downhill flows into the side of the ditch. Once the water enters the drainage ditch, it will flow downhill. This often requires drainage ditches to be angled across slopes to catch water and carry it away from problem areas.
- Plan your drainage trench to catch water flowing downhill or drain areas of standing water.
- A drainage trench must slope down at least 1 inch (2.5 cm) every 10 feet (3 meters) to properly drain water.
- To capture water and drain it downhill, your drainage ditch may need to curve.
- For a natural look, plan additional curves and bends.
To make sure your planned drainage ditch is sloped properly for adequate drainage, measure the slope of your yard. This will bulletproof your trench plan.
Excavate Your Trench
Your rock drain should be wider than it is deep. This is in direct contrast to French drains, which are often narrow and deep. For your rock drainage ditch, dig a trench to a depth of 18 inches (45 cm) and a width of 36 inches (90 cm). This will prevent erosion, washouts, and flooded drainage ditches.
- Dig your drainage ditch 18 inches deep.
- A rock drainage ditch should be twice as wide as it is deep. In this case, 36 inches.
- If you want to create a natural streambed look to your drainage trench, widen it in places, especially at bends.
Depending on the look you want to create, your drainage ditch can have gently sloping sides or straight sides. However, keep in mind that sheer sides are more prone to erosion and may need to be reinforced with a rock border.
Lay Landscape Fabric
Once your drainage ditch has been completed, line it with water-permeable landscape fabric. This will help combat erosion and prevent weeds from coming up from the bottom of the trench. Landscape fabric also works to contain gravel and keep it from being mixed with dirt, ensuring your trench continues to drain properly over time.
- Line the bottom and sides of your drainage trench with water-permeable landscape fabric.
- Extend the landscape fabric 12–18 inches (30–45 cm) past the side of the ditch.
An excess of landscape fabric is better than too little. In the following steps, we’ll fold excess landscape fabric over the gravel to create a barrier on top that prevents soil from infiltrating your gravel and giving weeds a place to root.
- Heavy-duty and durable for long-lasting weed control.
- Easy for you to install and set up.
- Keeps weeds out without blocking necessary air and water.
Pour an 8-inch deep (20 cm) layer of gravel or rock atop the landscape fabric in your drainage ditch. For best drainage, use large rock, such as #3 crushed stone which ranges from 3/4 to 2 inches in size. Alternatively, 3/4 inch gravel is adequate.
- Pour 8 inches of gravel into the bottom of your drainage trench, atop the landscape fabric.
- Use large-to-medium-sized rocks, crushed stone #3, or 3/4 inch gravel.
- Fold excess landscape fabric over the top of the gravel layer.
Avoid using small gravel, such as pea gravel. Larger rocks allow water to percolate and enter the soil. Small gravel compacts and prevents water from flowing through. This will lead to a flooded drain that doesn’t provide much benefit.
Top with Stones or River Rocks
Now that you have laid your gravel to help drain and distribute water while preventing erosion, top the landscape fabric and gravel with stones, river rocks, or an additional 2 inches (5 cm) of gravel. This will keep the landscape fabric in place while hiding it.
- Top your gravel layer with 2 inches of rocks, field stones, or additional gravel of your choosing.
- Use smooth river rock for a creek bed appearance.
While many different materials can be used as a finishing layer for your rock drainage ditch, it’s best to use medium-sized rocks to promote good drainage. Avoid sand and other materials that can prevent drainage or allow weeds to root.
Add a Border or Plants
To complete your drainage ditch, you can either leave it as-is with a grass border or place fieldstones and rocks alongside. Because the ground around the ditch will likely remain moist, consider planting it with lilies, irises, or horsetail rush.
- For a rocky stream look, place decorative field stones or large rocks alongside your drainage
For a garden atmosphere, plant canna lilies, cattails, horsetail rush, or blue irises.
Just because your drainage trench is functional, doesn’t mean it has to be an eyesore in your yard. Choose a look that you prefer and turn a utilitarian rock ditch into a landscaping focal point.
What Size Rock is Best for Drainage?
Large to medium-sized rock will provide the best drainage in a trench or ditch. Rock and gravel used to line a trench should be at least 3/4 inch in size. This is often sold as “landscape gravel” but can be found commercially as #3 crushed stone. Avoid sand, pea gravel, and other small rocks. They are prone to compaction and do not drain well.
- Use large to medium-sized rock.
- Landscape gravel, crushed stone #3, and 3/4 inch gravel are great for drainage.
- Choose an angular rock that avoids compaction.
- Do not use sand, round gravel, or small rocks. These drain poorly and are prone to sliding.
Angular rocks and gravel are the best material for drainage ditches. Not only do they allow water to flow through, but they also resist sliding. Pea gravel and round rocks often slide down slopes.
How Do you Make a Gravel Drainage Ditch?
To construct a gravel or rock-lined drainage ditch without a drainpipe,:
- Plan your trench to collect flood and stormwater and channel it downhill.
- Dig a trench 18 inches deep (45 cm) and 36 inches wide (90 cm).
- Line the trench with landscape fabric.
- Add a layer of gravel 8 inches deep (20 cm).
- Fold excess landscape fabric over the top of the gravel.
- Top landscape fabric and base gravel with decorative stone or river rock.
- Add a stone border or plant water garden plants alongside the ditch.
Using these steps, you can create a very effective drainage ditch that draws excess water away from problem areas and filters it through rocks to distribute the water underground. It’s up to you how much creativity you’d like to add to the project, if you desire, you can turn your drainage trench into a decorative dry creek bed.