The first questions I ask when I stand on a new site are: where is the water coming from, where is it going to go, and what’s going to happen when it gets there? Howard Cohen, Landscape Architect
Landscape drainage is a critical factor in the success of any landscape design project. And most Northern Virginia properties have pre-existing drainage problems that must be addressed within the scope of a landscape design project.
The first step for your landscape architect is to conduct a thorough site analysis and evaluation taking note of the existing slopes and elevation changes on the property, surface and groundwater (wet and dry areas), and soil composition. We want to be sure that rainwater is not puddling on hard surfaces but is directed to run off and sink into the ground. We want soil around plants and trees to drain efficiently so plants will stay healthy.
The Necessity of a Landscape Drainage Plan
The effectiveness of the drainage system on a property overall and techniques that support well-drained planting beds have a direct bearing on the health and longevity of your garden plants. A sound landscape drainage plan is comprised of two principal parts: one relates to hardscaping and the other to planting beds.
Drainage and Hardscaping
The drainage system is built into the hardscape. The landscape architect may specify permeable surface areas with buried drainage pipes and retention wells that allow water to percolate naturally back into the soil.
We often use slot drains along the perimeters of patios and walkways to take rainwater straight into the ground. We also adjust grading on the property to control the direction and flow speed of surface water. We may direct rainwater toward a natural slope or to an area where we’ve installed a small culvert or drain box.
Drainage and Plants
In Virginia, we have dense clay soil that stays wet. We try to select plants that can take sustained periods of moisture. We also plant in raised or mounded beds with sand mixed into the soil–which ensures that water drains well away from plants and keeps the roots dry.
A raised bed will usually have low retaining wall bordering it. Mounding doesn’t require hardscaping. In both, we use a balanced blend of sand, soil, and compost to build up the mound, so it is stable, provides nutrients and drains properly.
Drainage Solution 1: A Damp Yard Reclaimed
The owners of this McLean residence rarely used their backyard patio because it always felt damp and uncomfortable. During heavy rainstorms, water would sometimes flood the lower level of the house. A landscaping project not only beautified the backyard but permanently fixed their serious drainage issues.
We dug an infiltration trench in the front right corner of the side yard. All the downspouts from the house tie into it. An infiltration trench sinks about six feet into the ground. It is lined with fabric, filled with layers of sand, clean washed gravel and topped off with about a foot of well-draining topsoil. Excess water filters into the ground.
Although you can’t see it, this part of the drainage plan was vitally important the success of this landscape design project. If the property didn’t drain properly, plants and people would suffer from too much moisture. Making an outdoor environment beautiful is important, making it comfortable and fully functional is essential.
Drainage Solution 2: A Low Spot Becomes a Highlight
This Herndon residence had drainage problems that made it impossible to plant anything to make the front entry attractive. The ground sloped left along the front of the house toward a lot spot where water collected and pooled against the foundation.
A front entry landscaping project beautified the curb appeal of the home while solving the drainage problem.
We ran drainage pipes under the driveway to draw excess water away from the house, then built up the garden beds above the previous ground level and held them in place with a low retaining wall.
Drainage Solution 3: Beautiful & Practical
This Oakton residence sits on an expansive lot that had a combination of steep slopes and low areas. Extensive regrading and terracing made the backyard highly functional. A highlight of the drainage plan is the biofiltration sinks disguised by lush planting beds. The biofiltration sinks receive water from upper levels on the landscape and let it percolate naturally back into the ground—and at the same time feeding the moisture-loving bedding plants on the surface.
The Design You Don’t See
Drainage design is the part of every landscape design you will never see. But everything you see and enjoy above ground is supported by it. If you skip investing in landscape drainage to save a little money, you will end up with issues after the fact. And that could end up costing you more because you may have to remove expensive hardscaping and landscaping to install a solution.
All of the example projects began with a desire on the part of a homeowner to correct a drainage problem that was preventing them from using their yard or was interfering with the ability of landscaping plants to establish and thrive. If you feel that landscape drainage issues are preventing you from fully enjoying your outdoor living areas, contact one of our landscape architects to schedule a phone consultation.
If you’ve been thinking about investing in a landscape design project, our eBook: Expert Guide to Planning the Landscape Design of Your Dreams, is full of valuable information to help you get started.