Rockflow: smart water buffers made from fully circular rock wool

How do you make a city rainproof? In the face of increasingly frequent downpours, a legitimate question that many governments, landscape architects, engineering firms and policy makers are considering. ROCKWOOL Rainwater Systems has an answer - rock wool. How and why it works well, tell Corinna May, Marketing Manager, and Daan Los, Urban Climate Adaptation Advisor.

Stone wool in the fight against flooding during downpours? "Yes, definitely. Stone wool owes its fame mainly as an insulation material, but what not everyone knows is that it is also excellent in combating excess water," Corinna explains. "It acts as a water sponge, in this case underground. The dense fiber structure of stone wool not only captures the abundance of rainwater, it also filters runoff water, thus ensuring cleaner ground and surface water. Two birds with one stone, because that way you protect the city's natural water cycle at the same time." ROCKWOOL Rainwater Systems uses its Rockflow product for this purpose: smart water buffers made from fully circular stone wool. Here, ROCKWOOL is driven by the desire to look at climate change differently. "We speak of climate adaptation. We have to deal with increasing urbanization and the climate changing resulting in, among other things, heavy downpours and long periods of drought. So our message is: rethink urban water. Thus, we embrace the concept of sponge cities: cities that utilize their green infrastructure to prevent flooding but also heat and drought."

Klimaatwadi in Zoeterwoude

In the context of climate adaptation, rockflow is being used in an increasing number of cities to prevent flooding on the one hand, and to retain rainwater as a buffer for drier periods on the other. In the new housing estate Klaverweide in Zoeterwoude, these two functions are cleverly combined in a so-called climate wadi. Daan explains: "For the wadi at Klaverweide, only a narrow strip was available between the driving lanes and (green) parking spaces and all the cables and pipes. Under that wadi is a Rockflow infiltration package on which the surrounding paved surfaces can drain (with slokops as backup). On top of the Rockflow infiltration package, we installed a capillary fracture in the form of a gravel layer. This allows water to be retained for longer periods of time. On top of the gravel layer is an additional layer of Rockflow, about 10 cm thick, and on top of that a relatively thin layer of soil for the plants. Thanks to the extra layer of Rockwool, plants can draw moisture from this for about 4 weeks in drier periods."

Strong enough for tramway

That stone wool is very versatile is also attested to by the redevelopment of the Nieuwezijds Voorburgwal in Amsterdam. Here the Rockflow water storage and infiltration system is located under the streetcar tracks. As part of Amsterdam Rainproof, the streetcar tracks and greenery here had to be replaced and the layout changed. Part of the plan was also to collect rainwater during heavy showers. Daan: "The only space available to buffer and infiltrate water was under the streetcar tracks. So the special thing about this project is that concrete was poured directly on top of the rock wool elements, over which heavy streetcars then drive, which is of course not an everyday occurrence."

Meeting the challenge together

These projects prove that ROCKWOOL likes to think outside the box and look at possible solutions together with partners. Corinna: "Rockwool has been a tried and tested product for 80 years that also serves as an excellent water sponge. We are very keen to talk to partners who dare to experiment and want to take up the climate adaptation challenge with us. Our appeal is therefore to everyone who is responsible for or involved in climate adaptation, water and green space: dare to tread new paths and enter into dialogue with each other; there is a lot of innovative power and goodwill in the market. We must use this to together make our toolbox for climate adaptation as large as possible. And for stormwater management with rock wool? Please contact us!"