Floating treatment wetlands … and their closely related floating islands … are a manmade landscape element for bodies of water that have been made for centuries. The Native Americans of South America built islands made of reeds to build their houses and farms on to avoid attack by an expanding Incan warrior empire. Long after the Incan empire has faded away into history these people still live on Lake Titicaca in Puno, Peru, and now welcome throngs of tourists to their islands. In Southeast Asia, people have long used floating rafts of grasses supported by bamboo frames to clean hog waste lagoons. Nowadays, primarily driven by the need to manage nutrients in the water, floating treatment wetlands are used for a variety of purposes and made from a wide variety of materials.
While the islands have been around for centuries, they are undergoing some major changes with regards to their purpose and also the materials that they are made of. Islands can be made from a closed cell foam, or Styrofoam and coir fiber (i.e. coconut husks). They can be made in the traditional method of a bamboo frame supporting a thin mat planted with a variety of wetland plants. There are also products out on the market that are called floating mats which is a variant of this floating island technology. The idea of the floating mat is to stretch the mat over the pond and support it and place with posts buried on the side of the pond. The plants are planted in pre-drilled holes and their roots are thus suspended into the water. The mat itself does not have any surface area however, and nutrient removal is dependent on plant uptake. As such to remove the nutrients from the pond’s environment the plants must be removed and new plants need to replanted every six months or so.
So how do we pull up the hood and figure out what is going on with these floating islands? How do they clean water? Well, just like nature does it. Floating islands rely on the surface area of their material and also the inclusion of plants on the island to clean the water. The surface area of the island and the plants provides an ideal growing environment for the microbes that are extremely efficient at taking up excess nutrients from the water. The plants serve as a nutrient sink also as they take up nutrients to grow, but also to provide carbon and oxygen to the microbes that are growing in the island and water. Islands are built with a porous matrix to allow plant roots to grow directly into the water column where the roots can directly interact with the dirty water.
Another important way in which many islands can clean water is to use them as wave attenuation devices that prevent waves from striking a shore causing a constant resuspension of soil particles. This is done through the use of a 5-foot-wide strip anchored 4 to 10 feet from the pond’s shoreline and thus allows for a stabilization of the bank and results in less turbidity in the pond. In the final analysis the results of incorporating a floating island into your golf course pond is similar to having built a constructed wetland in that it results in fewer nutrients and suspended solids in the water that lower water quality, just without the need for permits, and messy and expensive site work.
The growing appeal of floating islands is that they provide a variety of services while out on the water looking good all summer long even during drought. Besides the functional value of cleaning the water of excess nutrients as discussed above, they also provide wildlife habitat for a wide variety of fish and animals and uncommon wetland plants. In addition to increasing a course’s biodiversity, they can be used as part of the infrastructure of the course, especially when the designer incorporates them into the original course design. Islands can be engineered to support walkways and benches and gazebos, or pretty much any light construction that you can think of. This characteristic can be used to create island bridges that that are turfed and considered playable on the course. If done correctly, this could be done with a floating green or a floating walkway that again doubles as a “living shoreline” that could be moved from time to time. Creativity and the need to keep the course playable would be the only limitations.
It might help to understand how these islands can be moved from time to time if I explain their physical structure and construction. Some islands are built up from a single module that can be attached to other modules much like building a Lego house, (yep, it’s that simple) to eventually form any size and shape island that is required. Island sizes vary …some are 100 square feet in size … and there are islands that have been built that are one acre in size. Golf course ponds will probably fall somewhere in the middle of that range. But whatever the size of your pond, a general rule of thumb is that you should cover five to 10 percent of your pond with the floating island to achieve a treatment effect and reduce nutrients. People do, of course, buy smaller islands so that they can add an attractive amenity to your pond.
So find out more about this exciting new tool for pond management. The technology has great potential to help keep water clean and add landscape elements to set a golf hole apart from all others.
Rob Crook builds islands in North Carolina for Floating Island Southeast. They travel throughout the east coast building islands that provide a variety of services from cleaning storm water and wastewater to providing wildlife habitat. Rob is enthusiastic about bringing your vision for new and wonderful floating islands in to safe harbor on your golf course.
Floating Island Southeast makes their islands as a licensed product called Biohaven® Floating Treatment Wetlands. The Biohaven® floating wetlands are made from 100 percent post consumer recycled plastic that is planted on top with a variety of both wetland and horticultural plants.
You can contact Rob about his company’s product by phone at home/office 919-918-7788 mobile 919-260-5082, or on the web at www.floatingislandse.com or follow him on Twitter at floatingisland2.