Smart water management system: the launch of Rockflow
Rockflow is a water management system developed by Lapinus (a part of ROCKWOOL) for urban areas with heavy flooding. Rockflow can buffer large amounts of rainfall in urban areas quickly and effectively.
This innovative system is used under built-up areas, such as squares, roads, streets and industrial sites, that suffer from severe flooding during heavy rainstorms. The system consists of thin (standard element 100 x 120 x 15 cm), light (less than 20 kg) stone wool elements that absorb the rainwater and then infiltrate it in a measured manner into the soil layer or drain it to the sewers. Lapinus is the first producer to apply stone wool elements as a water management system and to bring them onto the market. "The Rockflow elements provide an optimal water balance during heavy rainfall," says Daan de Kubber, Marketing & Business Development Manager at Lapinus.
Flooding can occur on stone surfaces during and after a heavy rainstorm because the excess water cannot drain away into the soil and through the sewer system quickly enough. If the rain is coming down in buckets over a short time, a huge amount of water has to be collected and drained. The sewage system cannot handle this enormous amount of water, which is why streets and cellars flood. Capturing and draining the water faster avoids flooding. The stone wool elements can absorb 95% of their volume of water and have a throughput of 200 metres a day. A cubic metre of Rockflow system can take up 950 litres of water in 8 to 10 minutes. "This is more than enough to create water management systems that meet local standards," says De Kubber. Once saturated, the stone wool element can allow the water to infiltrate the substrate or drain to the sewer gradually, spread over 24 hours.
De Kubber has been involved in the development of Rockflow from the very beginning. He says that buffering water with stone wool is a method that is widely used in greenhouse construction. "In greenhouses, it’s used for growing plants on. We have developed stone wool elements that can not only store huge amounts of water very rapidly, but are so strong that they can cope with the load of a full parking deck or trucks that drive over them.”
More and more municipalities are becoming interested in this innovative water management system. Within each municipality, there tends to be an area that is regularly flooded. "Not only has the rain become more intense due to climate change, the current design of the sewer system also contributes to the problem. The sewers in the Netherlands were built eighty years ago and were not designed for the capacity that is necessary today. The problem of excess water is becoming increasingly urgent.' De Kubber: “Rain showers are becoming more extreme due to climate change; the sewers can no longer drain away the water and the streets become flooded. This is happening while more and more surfaces are being hardened in the Netherlands. Resulting in even more damage. Municipalities are often liable for the damage caused by flooding. These municipalities thereby know that they need to take strong measures in the short term to combat increasing flooding."
Replacing the sewers is an expensive process. It is much cheaper to capture the surplus of relatively clean rainwater and to gradually drain it away or allow it to infiltrate the soil. Many urban areas in the Netherlands suffer from a lack of water. "It’s a waste to guide the relatively clean rainwater through the sewers to a water purification plant. Rockflow allows the collected clean rainwater to slowly seep into the soil, causing the water balance to be slowly restored,” says De Kubber.
The basic material of the system is stone wool, which is literally made of stone and therefore contains all the properties of stone: it is strong, porous, hardly deforms under pressure and is completely recyclable, thereby avoiding environmental damage. The system is made-to-measure, and adapts to the shape of an infrastructure project without losing its functionality. The water management system consists of modular stone wool elements that are installed below the ground level. The plates are buried under the built-up surface of the urban area, whereby the above-ground functions remain completely intact. During heavy rain, the water flows through the road drains to the lower part of the stone wool package. The hollow spaces between the stone wool fibres fill up with rain water. The road drains are connected to the Rockflow elements via a piping system. Because these elements are filled with water from the bottom, the air can escape through the ventilation channel at the top, so that the buffer can optimally fill with water.
Royal Haskoning DHV has been closely involved in the technical development of the water management system. Marc van den Heuvel, hydrology consultant, explains the benefits of Rockflow. "A major advantage of this system is that the infiltration surface is much larger than the regular crate systems or lava cases that are often used to drain water to the soil in built-up areas. The system is open on all sides in order to infiltrate water to the bottom. The lower side of the crate system or a lava case should not be counted as an infiltration surface, because this system silts up with dirt. The water that infiltrates from the Rockflow is filtered, clean rainwater, free from small clogging particles, as a result of which more rainwater infiltrates faster into the substrate.” In fact, the structure of the stone wool elements filters out any contamination from the inflowing water, so that the system does not become clogged with sand, sludge, algae and moss particles. If necessary, the water can be filtered in advance using filter pits. These filters are easy to replace and are also recyclable.
Van den Heuvel continues: "A further advantage of Rockflow compared to the crate system is that there are no filter cloths around the stone wool elements. The elements are applied directly against the ground layer. Filter cloths become quickly damaged, for example through maintenance work. Soil then flows into the system, but this doesn’t happen with Rockflow.” An additional advantage is the flexibility of the material. "In the case of underground work, a slot can easily be pulled through the elements to lay a cable, without affecting the operation of the water management system,” he explains. "Maintenance of these systems only needs to take place during the annual standard maintenance of the sewers," says Van den Heuvel.
The engineering office is constantly investigating how the Rockflow systems can be used sustainably as a salvage facility, taking the permeability and the groundwater level of the area into account.