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Key Takeaways

  • Good fairway drainage is an essential part of maintaining quality playing conditions and healthy turf. It also minimizes the impact of wet weather on course access and revenue.

  • The optimal depth for fairway drainage lines varies from less than 12 inches to more than 24 inches depending on soil type, climate and other factors.

  • Pipe size and spacing should account for expected water volume, soil type, topography and local climate. Proper analysis before installation ensures the system can handle peak water flow.

  • Backfill material must support soil structure and turf health while providing adequate drainage. Ensure an accredited lab tests the backfill material before making your choice.

  • There are often less-disruptive options than installing a network of pipes to address localized drainage issues. Knowing there's more than one way to solve a problem is reassuring.

  • 2-inch “turf flow” pipe is an increasingly popular fairway drainage option because it is less disruptive and it is effective for drying wet soils. You can trust this method for your course's drainage needs.

     

Drainage projects have always been a critical aspect of golf course maintenance operations. To consistently provide the best possible playing conditions, golf courses have installed miles of drainage pipes to improve playability in areas prone to wetness. Over time, various drainage techniques have been tested and new methods have emerged to achieve the desired firm conditions with less disruption and quicker results.

An area of many golf courses that garners attention for drainage is the fairways. Proper drainage allows superintendents to maintain firm fairways with good bounce and roll. It also helps courses remain playable after rain, reduces cart restrictions, and keeps turf healthy and resilient. Unfortunately, many courses have inconsistent fairway drainage at best and wet conditions can be a real issue.

This article delves into some of the details of executing a successful fairway drainage project. It will offer insights and best practices to help superintendents optimize water management and enhance playability. From selecting suitable materials to exploring less-disruptive alternatives, we’ll cover everything you need to know to upgrade the drainage in your fairways.

Optimal Depth of Drainage Lines

Installing drainage lines at the right depth in a golf course fairway is crucial for achieving the desired results. Typically, drainage lines on a golf course fairway range from 12 to 24 inches deep, depending on factors such as soil type, local climate and the specific drainage needs of the fairway. A general rule is that the top of the pipe should be at least 12 inches below the surface.

For sandy soils, which naturally have higher permeability, drainage lines may be placed at shallower depths (around 12 inches) since water moves more quickly through the soil profile. Conversely, less-porous clay soils often require drainage lines as deep as 24 inches to ensure adequate water movement and prevent surface pooling. The heavier soils tend to have poor drainage due to their compact structure and smaller pore spaces, which limit the movement of water. In a golf course fairway, deeper drainage lines are necessary in these soils because they need to be placed below the level where water tends to accumulate. This helps create a stronger gravitational pull for water to move down toward the drainage pipes. Deeper lines ensure that water can effectively percolate from the surface, preventing pooling or saturation that could damage the turf and disrupt playability. In contrast, soils with better natural drainage might not require such deep installations.

Fairway slope and contour also influence the optimal depth and placement of drainage lines. Areas with steeper slopes may require shallower drains to quickly capture and redirect surface runoff, while flatter areas might benefit from deeper drains to manage water that percolates more slowly. The drainage trench should maintain a minimum slope of 1% toward the outlet.

Selecting the Right Pipe Size and Spacing

Pipe sizing and spacing involves several key considerations, including the expected water volume, soil type, slope of the land and local climate conditions. The primary goal is to ensure the drainage system can efficiently handle peak water flow to prevent fairway conditions from being soft and/or unplayable.

The expected water volume is a critical factor. This is determined by calculating the drainage area and considering the average and peak rainfall intensities. Larger drainage zones and regions with high rainfall will require pipes with greater capacity. Standard sizes for perforated fairway drainage pipes range from 2 to 6 inches in diameter, and they typically run into a catch basin or larger mainline pipe to remove water efficiently. The most widely used sizes are 2-inch “turf flow” pipes for shallow trenches or 4-inch pipe for the deeper trenches found in a more conventional design.

The soil type also influences pipe size selection. In sandy soils, smaller pipes are typically sufficient because water can infiltrate the soil quickly and consistently over a broad area. Sandy soil has larger particles and greater pore spaces, allowing water to flow through more easily and enter the drainage system at a more-consistent rate. This rapid, uniform water movement through the soil reduces the risk of excess surface runoff, meaning the drainage system doesn’t need to handle large volumes of concentrated water entering through catch basins and other surface inlets. Water moves more slowly in clay or compacted soils, which means more surface water needs to be captured and carried by the drainage system. To handle this type of drainage effectively, pipes 4 inches in diameter and larger are needed. Soil permeability tests can help determine the appropriate pipe size based on how quickly water percolates through the soil profile.

The fairway's slope affects both pipe size and spacing. Steeper slopes can move water faster, potentially necessitating larger pipes to handle the rapid influx. Conversely, flatter areas may require careful design to ensure sufficient flow velocity within the pipes, which is sometimes achieved using smaller diameters to maintain higher pressure and prevent sedimentation.

Local climate conditions, mainly the frequency and intensity of rainfall events, significantly influences pipe size. In areas with frequent heavy rains, larger pipes ensure the drainage system can cope with sudden surges in water volume. Accounting for the risk of extreme rainfall events is becoming increasingly important in drainage design.

The spacing of fairway drainage lines is typically a standard distance ranging from 10 to 15 feet. This is common for most drainage patterns, whether they consist of a lateral or "flag" design, or the standard herringbone design used by conventional drainage systems. Two-inch drainage pipes require tighter line spacing than conventional 4-inch pipes; normally, 6-foot spacing between the lines is preferred. The smaller diameter of the 2-inch pipe reduces its capacity to carry water, so placing the lines closer together helps compensate by allowing for quicker water collection and removal, ensuring effective drainage across the area. The Hooghoudt equation is a drainage-spacing tool that can be used to determine the spacing of trench lines (GTC Staff, 2006).

Selecting the correct pipe size and spacing for a fairway drainage project requires a comprehensive analysis of water volume, soil type, land slope and local climate. By carefully evaluating these factors and possibly consulting with a drainage engineer, golf course managers can design a drainage system that improves fairway playability and turf health.
 

"Selecting the correct pipe size and spacing for a fairway drainage project requires a comprehensive analysis of water volume, soil type, land slope and local climate."

Choosing the Correct Backfill Material

Selecting the optimal backfill material for fairway drainage lines ensures the system's effectiveness and longevity. The ideal backfill material enhances water infiltration into the drainage pipes, supports soil structure and promotes healthy turf growth. When choosing backfill material, key considerations include its permeability, stability, compatibility with existing soil and impact on turf health.

Permeability is a primary factor; the backfill material must allow water to move quickly and freely toward the drainage pipes. Stability is another crucial consideration. The material should resist compaction and maintain its structure under the weight of the soil and turf above. This ensures that the drainage system remains functional over time, even under heavy traffic.

The impact on turf health is also significant. The backfill material should support root growth and provide adequate aeration for the turf. Fine materials such as silt or clay should be avoided, as they can reduce drainage efficiency and create a compacted layer that impedes water movement. On the other hand, many courses have used backfill material that drains too quickly at the surface, which leads to dry and desiccated turf in the pattern of the drainage lines.

The most commonly used backfill mixture is predominantly sand combined with a smaller percentage of peat or soil. This mixture is sometimes used to fill the entire trench, but sometimes straight sand is used for backfilling until the top 6 inches when the sand and soil/peat mixture is used. This maintains the necessary permeability while providing an adequate growing medium for roots. A drainage rate of 30-60 inches per hour is preferred for the straight sand portion of a system like this (Whitlark, 2020).
 

The ideal composition for a sand mixture is site-specific, but typical ratios include 80% sand and 20% soil; 75% sand and 25% soil; or 60% sand, 20% peat and 20% soil. The goal is to achieve moisture retention in the rootzone of approximately 15%-20%. Always have an accredited soil testing laboratory test the mix that will be used to confirm performance characteristics.

When backfilling a drainage trench, the mixture of sand and soil should be designed to promote drainage while also providing stability. The ideal ratio depends on the specific drainage requirements and the type of soil you're working with. For high drainage needs, a mixture of 70%-80% sand and the remainder soil allows excellent water movement while the soil provides structure and helps hold moisture for healthy turf over the trenches. For moderate drainage needs, a mixture closer to 50%-60% sand and the remainder soil is more balanced, providing a good level of drainage while also keeping adequate moisture for turf health.

I recommend using a coarse sand for backfill mixes because fine sand can compact too much and reduce the drainage effectiveness. Gravel is used around drainage pipes in fairway installations to facilitate water flow and prevent soil from clogging the pipe. It creates a porous layer that allows water to filter through efficiently while providing structural support to the pipe. Typically, a layer of gravel about 4-6 inches deep is placed both beneath and around the sides of the pipe, ensuring it is fully encased for optimal drainage performance. Additionally, using clean, coarse gravel helps prevent soil migration and enhances the overall lifespan of the drainage system.

Nonwoven geotextile fabric can also be used around drainage pipes in fairway drainage projects to prevent soil and sediment from entering and clogging the drainage system while still allowing water to pass through. This helps ensure long-term functionality by keeping the pipe clear of debris and reducing the need for maintenance or repairs.

Exploring Less-Disruptive Alternatives

Installing drainage pipes on a 10- to 15-foot spacing throughout large fairway areas will improve playing conditions and turf health, but it can also be highly disruptive work that affects play for days or weeks. Fortunately, several less-disruptive alternatives can effectively manage water and improve turf health in wet areas. These include sand injection or slitting to create sand channels, surface grading, implementing a fairway topdressing program and using various aeration practices.

Sand channel drainage, a system that forgoes pipes, involves creating narrow sand-filled trenches to enhance water infiltration and movement through the soil. This method is particularly effective in areas with high rainfall or poor soil drainage. The sand-filled trenches, typically dug to a depth of 6 to 10 inches, allow excess water to percolate quickly through the soil profile, reducing surface waterlogging and promoting healthier turf. Sand channel drainage without pipe is less disruptive than drainage with pipe because it involves shallower, narrower trenches. Instead of excavating deeper trenches to accommodate the pipe, only a narrow cut is needed to fill with sand, which minimizes disturbance to the turf and surrounding soil. This approach preserves more of the existing grass and root structure, making it easier to restore the surface after installation.
 

Surface grading involves reshaping fairway areas to help water exit the playing surfaces or enter the drainage system through basins. Creating gentle slopes and contouring the land can direct water away from high-priority areas and toward drainage points. The extent of disruption caused by surface drainage improvements can differ significantly based on the specific nature of the drainage problems and the surrounding topography. In some cases, addressing the issue may be relatively simple. Making a small cut to enhance surface water flow can have a substantial impact with minimal disturbance in some situations. However, in areas with extremely flat terrain, more-intensive measures may be required, such as importing additional material and regrading the entire fairway to facilitate better water movement. In many cases, an effective method to minimize disruption is intercepting surface water before it reaches the fairway, using techniques like drainage swales or diversion channels. This approach can improve water management without directly impacting the fairway's structure or playability.

Sand topdressing is another effective method to improve a fairway’s ability to absorb and drain water. Regularly applying a thin layer of sand to the fairways increases permeability and reduces the amount of water that lingers at the surface. This practice also helps prevent thatch buildup, which can impede water infiltration. Over time, sand topdressing creates a more uniform and resilient turf surface without requiring extensive excavation. However, there are many important considerations involved in a successful fairway topdressing program and if you aren’t careful, you can spend a lot of money and create more problems. The Green Section Record article “Figuring Out Fairway Topdressing” provides an in-depth look at how to plan and implement a fairway topdressing program.

Aeration practices, such as core aeration or spiking, can significantly improve fairway drainage with minimal disruption. Aeration involves perforating the soil with small holes that allow air, water and nutrients to enter the rootzone. This process alleviates soil compaction and enhances water movement into and through the soil profile. Hollow-tine aeration also removes organic material that can impede fairway drainage.

Conclusion

Fairway drainage is crucial for maintaining healthy turf and quality playing conditions. If your fairways need significant drainage improvements, management should strongly consider hiring an experienced contractor rather than attempting a large fairway drainage project in-house. The maintenance team is usually very capable of performing drainage work, but they may not have the tools or the time to do it efficiently and they may be drawn away from other critical work on the course. Hiring a contractor can be expensive, but if you consider the costs of poor drainage – like poor playing conditions, lost cart revenue and additional fungicide applications – the investment in better drainage will eventually pay for itself. For those looking to upgrade fairway drainage, consult with a USGA agronomist in your area for valuable guidance on planning the project.
 

References

Greenkeeper Training Committee (GTC) Staff. (2006). Drainage explained. Greenkeeper International, November, 45-47.

Whitlark, B. (2020). No drain, no gain. USGA Green Section Record, 58(22).