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Blog Article

Why bunkers wash out and how Capillary Bunker liner offer a long-term solution for the problem

Editorial Team
Why bunkers wash out and how Capillary Bunker liner offer a long-term solution for the problem
January 15, 2024

Marco Simone. Rome, Italy

Ask any golf course superintendent or maintenance staff member about the one maintenance issue they absolutely dislike, and the answer is most likely to be: bunker washouts. These occurrences, triggered by heavy rain, can impact playability for days after the rain by causing silt contamination of expensive bunker sand, consuming precious maintenance staff hours for repairs, and the cycle repeats with the next shower.

While bunker washouts can be a frustrating challenge, understanding their root causes is crucial for effective prevention. The fact is that while rain might be the proximate cause of washouts, there are two ultimate causes.

Why do bunkers wash out?

1. Direction of surface water flow: Poor surface drainage and golf course design that directs water into bunkers.

2. Poor internal drainage: Inadequate golf bunker drainage that allows water to build up on the faces, leading to sand movement during rain. Steeply sloped bunkers are especially prone to washouts and contamination.

Frequent washouts not only consume financial resources and demoralize maintenance staff, they have an impact on both short-term and long-term playability of the golf course. Over time, they can also lead to major issues such as sand contamination with soil. This contamination further affects golf bunker drainage, causes compaction, and slows down percolation/infliltration rates of the sand, posing a long-term concern for sand quality, and bunker playability and player satisfaction. The frustrating cycle continues.

Washed out bunker with a lot of sand contamination

So, is there no long-term solution to golf bunker washouts?

There is. While rain may be inevitable, bunker washouts are not. In this blog, we will briefly discuss the various methods golf courses use to prevent bunker washouts first. We will then delve into the details of Capillary Bunkers – a cutting-edge bunker liner that is proven to rapidly drain excess water while retaining adequate moisture in bunker sand, creating optimal playing conditions in golf course bunkers.

Different ways to prevent washouts

One of the most common methods of reducing bunker washouts is installing bunker liners.

These liners, usually made of geotextile or polyethylene, protect the sand from contamination both by the soil on the base and on the faces of bunkers. Effective bunker liners prevent soil from eroding and contaminating the sand. By keeping the soil in place on the face of the bunker, the sand remains clean and water moves rapidly through non-contaminated sand, reducing washouts. The liner also protects soil from clogging the drainage system beneath the bunker.

Fabric bunker liner is common but aren't often a long term solution to bunker washouts

Despite their benefits, it is common knowledge in the industry that most bunker liners for golf courses are not invincible. Yes, they reduce washouts and contamination but severe storms render most of them useless. Additionally, the problem with conventional bunker liners is that, after a few years, golf courses find that they stop functioning as designed. The liners degrade or rip, losing their efficacy— a significant investment literally gone down the drain.

Another method, recommended by the USGA, involves installing plastic no-dig landscape edging near bunkers to divert surface water away from the sand when rain is imminent. However, in areas or seasons that see regular rainfall, this edging might need to be a permanent installation – not an ideal solution either. Moreover, the process of installing and removing the edging is maintenance-resource intensive, taking the attention of staff away from other areas in the course.

Are bunker liners a long-term solution to bunker washouts? 

The short answer is no - but it could also be yes. It all comes down to the structure of the liner. To begin with, liners can be divided into three separate categories: 

  • Permeable Liners: These include porous aggregate liners and fabric liners. They allow for water infiltration to some extent, either by letting water pass through materials like fabric or by supporting rapid drainage through aggregates. Their primary function is to stabilize sand and reduce contamination while facilitating some degree of lateral water movement.
  • Impermeable Liners: This category includes liners that do not allow water to penetrate, such as specific impermeable synthetic liners. Their main function is to completely block water from moving through, thereby preventing contamination from the subgrade but potentially requiring additional drainage solutions to manage water accumulation. This is not always possible and depends on irrigation amounts and how steep faces the bunker has.
  • No Liner/Sod Liner: This approach involves either not using a manufactured liner or using sod as a natural barrier. Sod liners use grass and its root system to minimize sand contamination without significantly affecting water permeability. This method relies on the natural properties of soil and vegetation to achieve a balance between stability and drainage, without the use of synthetic or processed materials.

As the above liner types' structure varies, one could typically say the proneness to washouts increase with the degree of impermeability. Liners such as geotextile and to some degree fabric doesn't let water go through the liner itself, but depends on diverting it to the drain lines. This cause two issues: 

  1. Often, more drain lines are needed which increase the capital expense of constructing the bunker itself
  2. If the water can't enter the drain lines fast enough, water will back up in the sand and onto the faces. This is what ultimately will cause washouts and bunker failures.
Using a liner that is not permeable, such as fabric or geotextile, will cause washouts if water can't enter the drain lines fast enough

To conclude, impermeability in a liner increases likelihood of washouts significantly. This is why we recommend either sod or no liner, or preferably a porous aggregate.

Introducing Capillary Bunkers

This brings us to CapillaryFlow bunker liner technology — Capillary Bunkers. What sets it apart?

Capillary Bunker Liner installed in a bunker, right before sand placement

Effective moisture control is crucial for bunker performance. As sand dries out on steep bunker faces, the risk of plugged ball lies and washouts during rain events increases. Capillary Bunker liners for golf courses swiftly drain excess rainwater while redistributing moisture to bunker sand during dry weather, retaining optimal moisture in the sand, preventing washouts and migration of sand from faces, and ensuring impeccable playing conditions in any weather and terrain.

But how is it possible for a bunker liner to drain excess water as well as move water upwards to moisten dry sand on the bunker face?

Capillary Bunker liners are made of Capillary Material, a patented pervious cement and polymer material and the only building material to rapidly drain water while also moving it upwards. The Capillary Material’s ability to rapidly drain excess water and move moisture up to the sand in dry weather is one major reason why Capillary Bunkers are a major improvement on conventional bunker liners.

The Capillary Material

Introducing Capillary Wash Box

Capillary Wash Box, a value add-on to Capillary Bunker liners, is another CapillaryFlow innovation. The Wash Box enables golf courses to remove contaminants such as algae, debris, silt, clay, and organic pollutants from the bunker sand by simply washing it. In doing so, it preserves the sand’s percolation rate, color, and desired playing properties, while also eliminating the need for frequent sand replacement.

<<<Read more: Sustainable bunker care: Why you should never add more sand to your bunker base to dry it out>>>

This is important because sand can cost between $30 and $200 per ton in the US, depending on location, sand quality, source and transport costs. But its lifespan can be as short as a few months if severe storms occur shortly after the sand is installed. Regularly washing bunker sand with Capillary Wash Box protects a golf course’s investment in sand.

Washing the sand will improve the sand's performance and looks, while it also saves you a lot of money

Thousands of bunkers around the world, including many of golf’s top 100 courses, have successfully been renovated with Capillary Bunkers. On top of drastically improving the playability of bunkers, CapillaryFlow clients experience significant maintenance savings and ROI within five year. Learn more about what the ROI of different bunker liner alternatives are here: Bunker Liner ROI

Marco Simone, 2023 Ryder Cup venue, have Capillary Bunkers installed

At CapillaryFlow, we're so confident in our bunker liner technology that we offer an industry-leading 15-year structural and drainage performance guarantee on our complete Capillary Bunker system and equestrian sand footing solution, including liner, vaults, and wash boxes.

All you stand to gain with the world’s best bunker liner

To recap, here are the benefits of installing Capillary Bunkers.

  • A bunker drainage system that works: CapillaryFlow’s bunker liner system removes water from bunker sand at a higher flow rate than current bunker liner drainage systems and also completely stops sand from moving into bunker drainage systems.
  • Unique bunker lining material engineered for all courses: The patented CapillaryFlow bunker lining material has proven itself to be effective in even the harshest conditions – from drought to heavy storms, and in freezing and sun-drenched weather conditions.
  • An efficient ecosystem of bunker lining products: The Capillary Bunker liner and its bunker lining products creates an ecosystem that enables you to create the most beautiful and long-lasting bunkers out there with durable edges and washable bunker sand.
  • Wash your sand instead of an expensive sand replacement: Capillary Wash Box enables golf courses to remove contaminants such as algae, debris, silt, clay, and organic pollutants from the bunker sand by simply washing it. This helps you preserve the sand’s percolation rate, color, and desired playing properties, while eliminating the need for frequent and expensive sand replacement.
  • Bunker liner products that lead to significantly less maintenance: The Capillary Bunker lining material, Capillary Wash Box and Capillary Edge provides massive benefits for any course crew. This includes no migration of sand from bunker faces, no waterlogged bunker bases, no need to replace bunker sand, and reduced edge-trimming. 
  • Design freedom for bunkers: The angle of repose is used to set a maximum slope for bunker faces to help limit dry sand moving down excessively steep slopes. But with Capillary Bunker liner optimal moisture control you can design steeper bunker faces because the optimal moisture in the sand increases the friction coefficient of the particles, allowing golf courses to design steeper and more stable bunker slopes. This is due to the Capillary Material’s property to not only rapidly drain, but also move moisture back up to the sand again when needed. 
  • Quick and easy installation, all year round: CapillaryFlow bunker liners are easy to install. They can be installed by your in-house team with local materials and minimal tools, or by a local contractor. Capillary Bunkers gives you the flexibility to schedule installation during your off-season to avoid closing during peak playing seasons. The bunker is ready to be used again just 24 hours after installation.

But don’t just take our word for it. Capillary Bunker liner for golf courses have been installed in over 1,500 venues across the globe, bringing joy to golfers worldwide. This includes some of the world's top 100 golf courses, from Ryder Cup to PGA venues. Below, we provide a number of testimonials from satisfied superintendents and golf course owners. 


Case study 1: “Six years on, the bunkers still drain as they did the first day”

Six years after Dubsdread in Orlando, the oldest public course in Central Florida, installed Capillary Bunkers, Superintendent Alan Lichter is extremely happy with their performance.

“I love them,” he said. “They are still draining as they were the first day. We had seven tenths of an inch of rain last night, there’s no water in the bunkers.”

Given the extremes of the Florida climate, Lichter’s bunkers have had to face up to some pretty severe weather – and he says they have come through with colors still flying. Even after Hurricane Ian dumped 11 inches of rain on Dubsdread in September 2022, the CapillaryFlow Bunkers still performed. “It took one person – me – about 12 hours to fix the bunkers after Ian!” said Lichter. “Before we installed the CapillaryFlow bunker liner, it would have needed three guys working solidly for a week.”

Case study 2: “Three hours on the bunkers after a storm, and they’re pristine again”

Even before Jim Sedrel joined as superintendent of Hyperion Field Club in Iowa in 2017, he recalls, the discussion around the club was: “‘Our bunkers are horrid, we need to rebuild them.’”

He soon witnessed the issue first-hand. “Any time we got a two-inch rain, we would be 40-60 man hours putting our bunkers back together,” he said. “There would be silt and soil mixed in with the sand, and the bunkers would be crusty and horrible. It was awful for the members and totally demoralizing for my crew.”

Sedrel realized that the usual fixes were only short-term solutions and advocated for a complete bunker renovation. The club proceeded with a comprehensive bunker renovation and installed Capillary Bunkers in three phases between 2018 and 2022.

Sedrel is very happy with his new bunkers.

“From 40-60 man hours after rain, we’re now at a point where two guys spend three hours on the bunkers, and they’re pristine again,” he said. “We might still see a little bit of washout, but that only happens where, for architectural reasons, we can’t prevent the water coming off a green and into a bunker. We have 100 year old push up greens, and water does sheet off them. The bunkers perform fantastically, and it’s the CapillaryFlow Bunkers liner that we have to thank.”

Case study 3: Capillary Bunker liners: The ‘best product in the market

At The Breakers Palm Beach, a luxury oceanfront resort in Palm Beach, Florida, the director of golf and grounds, Mark Reid, is using Capillary Bunkers technology and the Wash Box to preserve his sand.

“We use Capillary Bunkers technology to ensure top-quality performance at both our Ocean Course and The Breakers Rees Jones Course,” said Reid. “Previously, when experiencing rain in South Florida, we would have to decontaminate the bunkers every time we had a washout, and once the sand starts to move, the sod would not be far behind. It took more than 200 man hours to put the bunkers back together,” Reid said.

He added: “Upon researching and conducting a trial in 2017, prior to the last Ocean Course renovation, we experienced very little washout after storms once the technology was implemented. I knew then that Capillary Bunkers was the best product on the market to meet our needs.”


Read more testimonials:

Saving money from day one at Oakwing Golf Course, Louisiana

Hurricane can’t hurt new CapillaryFlow Bunkers at Grande Dunes, Myrtle Beach, South Carolina

Saving sand at Royal Marrakech in Morocco

‘The product is amazing – I wish I’d had it years ago’: Kinsale Golf Club, Ohio

‘The results have been consistently excellent’ at Laguna National Golf Resort, Singapore

CapillaryFlow solving bunker problems at Loch Lomond in Scotland


Want to know more about our products?

Are you interested in how we can help you reduce washouts, maintenance and have bunkers with optimal performance & washable sand? Contact us!


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