Why water retention systems?
The consequences of the climate change are and will be the challenge for our and our next generation. On the one hand, we face temperature increase. On the other hand, we have to cope with heavy and unforeseen rainfalls, causing flooding and severe overloads of the storm water systems in cities. This combined with the trend towards urbanization and the increasing wish towards “green, more biodiverse living space” to fulfill our basic needs, challenges our society.
The reclaiming of land and subsequent sealing of natural soil by urbanization is one key driver for the flooding issues. Since rainwater cannot percolate anymore into the ground, water runs off straight into the storm water system, causing overload of the storm water system, potentially combined with flooding. The small water cycle is more and more disturbed as there is no time for water to evaporate.
When equipping a basic trafficable roof with defined water storage elements in combination with an adjustable flow control system the trafficable roof transforms into a water retention and water management system. Based on rainfall runoff models, these systems are designed to store calculated water volumes over a specific period (e.g. 24 hours) and to relieve calculated water volumes into the storm water system.
The Nophadrain Water Retention Systems
Nophadrain has developed water retention systems for roofs with extensive and intensive vegetation; and for trafficable pavement. The base of these systems are the various ND WSE Water Retention Elements in combination with the ND AFC-200 Adjustable Flow Control. The water storage capacity of the elements varies between 48 and 143 l/m².
Combine water retention and water buffering in one
To distress the storm water system, typical water retention systems are designed to store a defined capacity of water (l/m²) underneath the vegetation and substrate and to relieve it over a specific time period with calculated run-off rates. By this, water is in fact stored on the roof but just a minor part of it can be made available/accessible for the vegetation.
To make even more water available for the vegetation, Nophadrain recommends to combine all water retention systems of green roofs with either our ND SM Substrate Panels or ND WSM Water Reservoir Panels. Both are made of hydrophilic (water absorbing) mineral wool and differ in water storage capacity and density. Whereas the ND SM Substrate Panels (available in 25 mm and 50 mm) have a density of 80 kg/m³ and water storage capacity of 15 or 30 l/m² offers the ND WSM Water Reservoir Panel (available in 50 mm) a density of 120 kg/m³ and water storage capacity of 40 l/m².
Both products are installed above the water retention layer and do buffer water up to their saturation point. By this:
- more water is made available for the vegetation,
- the important evapotranspiration and subsequent water cycles are being fostered and
- only excess water will be discharged into the retention layer.
Why different densities?
Air volume content and compression strength can be determined with the differentiation in density. ND SM Substrate Panels have a density of 80 kg/m³ and a limited compression. Therefore, the ND SM Substrate Panels can be classified as substrate substitute and their composition height can be deducted from the overall substrate height. These features make the ND SM Substrate Panels particularly suitable for extensive green roof applications. ND WSM Water Reservoir Panels have a density of 120 kg/m³. This improves the compression strength even further and limits the compressibility even more. This makes ND WSM Water Reservoir Panels especially suitable for any application where higher substrate thicknesses, e.g. biodiverse, semi-intensive, intensive green roofs, are used.
Extra filter functions
This is not all – due to their specific structure, the ND WSM-50 Water Reservoir Panels also function as extra “filter layer”. This allows the use of substrates with higher organic content, enabling an even more biodiverse vegetation with increased transpiration and evaporation. True to our motto "Catch it,, Keep it, Re-use it".
At the top of this page, you can download the folders per application.