Surface Drainage and French Drains Solve Different Water Problems
When water collects in a backyard, homeowners often assume they need a French drain.
Sometimes they do.
But a French drain and a typical surface-drain system are designed to address different types of water.
Choosing the correct Drainage system starts by determining where the unwanted water is coming from.
Is water flowing across the surface during rain?
Is a downspout dumping water into a patio?
Or is the soil remaining wet because water is moving through the ground?
The answer determines the solution.
What Is a Typical Surface Drainage System?
A typical landscape drainage system is designed primarily to collect and move surface water.
This may include rainwater flowing across:
Lawns
Patios
Walkways
Driveways
Artificial turf
Planting areas
Low areas within the property
Common components can include:
Area drains
Catch basins
Channel drains
Trench drains
Solid underground drainage pipe
Downspout connections
Pop-up emitters or other appropriate outlets
The system works by establishing grades that direct water toward collection points.
The collected water is then transported through solid pipe toward an appropriate discharge location.
Surface drainage is commonly useful for:
Water pooling on patios
Runoff crossing walkways
Water collecting in low lawn areas
Roof runoff
Driveway drainage
Pool-deck runoff
Water gathering near outdoor living spaces
Good surface drainage starts with grading.
A drain cannot effectively collect water if the surrounding surface slopes away from it.
What Is a French Drain?
A French drain is generally designed to intercept water moving through saturated soil rather than simply collect water sitting on top of the ground.
A traditional French drain typically includes:
An excavated trench
Perforated drainage pipe
Clean drainage rock
Filter fabric or an appropriate separation system
A properly designed outlet
Water enters through the surrounding stone and perforated pipe and is carried away from the problem area.
French drains may be useful where:
Soil remains chronically saturated
Water moves through a slope
Subsurface water affects a retaining area
Seepage develops along portions of a property
Groundwater conditions contribute to wet landscape areas
A French drain should not automatically be installed simply because standing water is visible.
First determine whether the actual problem is surface runoff or subsurface moisture.
The Biggest Difference: Where the Water Is Coming From
A simple way to think about the difference is:
Surface drainage captures water above the ground.
A French drain intercepts water moving through the soil.
If rainwater runs across a patio and collects at a low point, an area drain or channel drain may be the more appropriate solution.
If water is moving through saturated soil along a slope, a French drain may be part of the solution.
Some properties need both.
When a Combination System Makes Sense
San Diego properties often have several water sources occurring at the same time.
For example:
Roof runoff may discharge near the house
A patio may direct surface water toward a planting bed
A hillside may introduce subsurface moisture
Irrigation may oversaturate soil
A driveway may slope toward the garage
A complete system might therefore use:
Catch basins for low areas
Channel drains along hardscape
Solid pipe for downspouts
A French drain for subsurface seepage
Each component should have a specific job.
Combining systems without understanding the problem can create unnecessary expense without actually improving drainage.
Drainage Should Be Planned With Hardscape
Patios, retaining walls, driveways, walkways, and other permanent improvements change how water moves through a property.
Professionally planned Hardscape And Concrete Contractor improvements should therefore be coordinated with drainage elevations before concrete or paving is installed.
Once finished surfaces are completed, correcting poor slopes or adding underground pipes can require cutting or removing new hardscape.
Planning them together is usually much more efficient.
Irrigation Can Create Drainage Problems Too
Not every wet area is caused by rain.
Broken irrigation lines, leaking valves, excessive watering, and sprinkler overspray can create conditions that look like natural drainage problems.
Before installing a major drainage system, inspect the Irrigation.
Ask:
Does the area stay wet when there has been no rain?
Does water appear after an irrigation cycle?
Are valves leaking?
Are sprinklers watering hardscape?
Is runoff moving downhill from another irrigation zone?
Fixing the source of the water should come before building a system to continually drain unnecessary irrigation runoff.
Start With a Complete Site Evaluation
Drainage is rarely solved by simply installing a pipe in the lowest part of the yard.
A professional evaluation should consider:
Property elevations
Soil conditions
Roof runoff
Existing drains
Irrigation
Patios
Walls
Slopes
Neighboring properties
Appropriate discharge locations
This is why drainage should be part of the overall Landscape Design Process.
Water needs to be planned just as intentionally as patios, planting, walls, lighting, and outdoor living.
Which Drainage System Is Right for Your Yard?
Choose the solution based on the water problem—not the name of the drain.
Surface drains are generally used to collect visible runoff and standing surface water.
French drains are generally used to intercept subsurface water moving through saturated soil.
Combination systems may be appropriate when a property has multiple sources of water.
Nature's Elements Landscaping can evaluate the property and help determine which approach makes sense for the site.
The right drainage system begins by understanding where the water is coming from and where it needs to go.
