Sports fields are not just venues for athletic events; they are multi-purpose spaces that require proper maintenance and efficient stormwater management. After all, there’s more at stake than disappointment when a highly-anticipated game or tournament is canceled due to heavy rain. Rainouts can cause financial losses in the tens or hundreds of thousands of dollars for college and professional games.
While fields can become soggy, muddy, and unusable without effective drainage systems, using proper surface drainage techniques can prevent turf damage, reduce safety hazards, and eliminate the need for expensive repairs. Sports field designers and managers prioritize installing sophisticated drainage systems to facilitate the efficient flow of water off the field to protect their athletic facilities. Proper field drainage prevents muddy soggy conditions and promotes healthier turf growth while reducing the risk of injury to players.
Contouring Athletic Fields for Positive Surface Drainage
For adequate surface drainage, a field should be constructed or renovated to encourage water to flow naturally away from the playing surface. This type of construction is an exacting process called contouring, and it’s the cornerstone of any effective drainage system.
Contouring, or grading, refers to the slope and contour of the field, which determines how water flows across the playing surface. It should have a consistent slope that directs water to flow toward designated drainage areas.
It’s essential to balance establishing a level playing field and providing an adequate drainage slope. Contouring parameters are specified for different sports and should be carefully followed to minimize problems with reduced visibility, increased player fatigue, and the dangers associated with uneven playing surfaces.
There are two basic contour design types: crowned and flat fields.
Crowned Fields
A crowned field has a higher point in the center, which slopes gently towards the sidelines. This design helps ensure proper drainage by directing water away from the playing surface. However, it is vital to maintain a gradual slope to prevent excessive water runoff and uneven playing conditions that impact the game.
Flat Fields
Flat fields, however, have a consistent slope in one direction or to one side. While flat fields may be more cost-effective to construct, it is crucial to ensure proper grading and contouring to prevent water from pooling on the playing surface. One-sided contouring can also affect play and exacerbate some problems that exist with crowned fields.
Internal Drainage Systems
In addition to surface drainage, certain types of internal drainage systems are increasingly popular for enhancing the overall effectiveness of drainage for natural grass fields by quickly removing excess water from the soil profile.
Pipe Drains are the traditional internal drainage system for artificial turf installations. They are typically constructed using corrugated plastic pipes buried between 18 inches and 3 feet deep. The trenches are filled with gravel or coarse sand to promote water flow into the drains. The trenches may also be lined with woven geotextiles to prevent water from soaking into the soil. While they are effective for artificial turf, they’re often not as effective in natural soil, especially if the ground above them is dense or saturated.
Strip Drains have become increasingly popular for natural grass fields as they offer more effective water removal than pipe drains. Strip drains are narrow trenches, usually only 2 - 4 inches wide, installed up to 18 inches deep using specialized trenchers. The channels are covered with metal, plastic, or concrete grates, installed flush to the field surface, and perforated to allow water to pass through.
Water that enters a strip drain flows to a perimeter collector for storage and reuse. Strip drains can be installed in existing turf with minimal surface disturbance, making them a convenient option for field renovations. They’re often employed for perimeter drainage but are also helpful for more comprehensive drainage management.
Sometimes, an impermeable liner may be installed in the trenches to prevent the collected water from waterlogging the soil or to minimize erosion. Water flowing through a strip drain at a high velocity may erode the ground around the drain, causing the drain to become clogged and reduce its effectiveness. In severe cases, erosion can cause the strip drain to collapse.
Sand Slit Drainage systems are installed by cutting narrow slits no more than 8 inches deep, intersecting at right angles to a series of sub-drains. These trenches are filled with gravel and topped with sand, forming a matrix across the entire field, which allows water to rapidly drain from the playing area. In natural grass playing fields, sand slit drainage also offers improved soil aeration and moisture control while keeping the playing area in good condition.
Choosing the Right Drainage System
When selecting a drainage system for your sports field, several elements need to be considered:
Water Removal
Consider the recent rainfall data in your area to determine how much water needs to be removed from the field and within what time frame. In many parts of the country, rainfall patterns have shifted to fewer but substantially more intense storms. The drainage system should be capable of efficiently handling the potential volume of water released during these increasingly heavy rain events.
Soil Type
Take soil samples from several different locations around your field to understand the variations of soil composition, as different soils have unique drainage characteristics. Coarse soils like sand generally drain better than fine soils like clay. The drainage system should be tailored to suit the specific soil conditions.
Budget
Consider your budget for the drainage system installation. While investing in a high-quality system is essential, balancing cost-effectiveness is also crucial. Work with your designer and installer to develop a design that represents a fair balance between the two while meeting the unique needs of your athletic field.
The Role of Geomembrane Liners in Sports Field Drainage Systems
Geotextile membranes, such as reinforced polyethylene (RPE) liners, can significantly enhance the performance of sports field drainage systems. These impermeable membranes prevent water from seeping into the ground, allowing rainwater to travel smoothly to reservoirs or treatment areas. Eliminating seepage is particularly important in regions with high water tables, heavy clay, or expansive clay soil where excess moisture can affect the structural stability of the field.
RPE liners are an excellent choice for sports field drainage, offering long-lasting performance and minimal maintenance requirements. RPE liners can last more than 20 years in these applications, providing significant cost savings compared to other materials.
Ultimately, sports field drainage systems are key for optimal playability and performance. By implementing effective surface drainage techniques and incorporating internal drainage systems like pipe drains, strip drains, and sand slit drainage, you can prevent waterlogging, reduce the risk of injury, and promote healthier turf growth.
Investing in a well-designed and properly maintained drainage system will prevent rainouts and financial losses and provide athletes and spectators with a safe and enjoyable playing experience. Prioritizing proper drainage in your sports field management plans provides the best conditions for athletic success.
