Can green roofs prevent flooding?

Green roofs contribute to flood prevention and mitigation by absorbing and buffering stormwater. Depending on the amount of water storage needed within your project and the roof construction, you can choose between a regular green roof, a Detention Roof, or a Retention Roof.

Regular green roof

Green roofs buffer water in the plants as well as in the underlying substrate and drainage layer. Water will return to the atmosphere through evaporation or is released slowly to the sewage system.

Detention Roof: lightweight solution for sloping roofs

As with a regular green roof, the plants and substrate layer of the Detention Roof have a water-buffering effect. In addition, the underlying layers ensure that a larger quantity of rainwater is temporarily collected and drained away. Another big advantage of this roof is that it has a relatively low saturation weight and can be applied to existing roofs with a slope of 2 degrees or less. You can find more information at

Download technical drawings Detention Roof

Retention Roof: for flat zero fall roofs

The Retention Roof is the perfect solution for roofs without a slope that need to buffer more water than a regular green roof. The water is collected in the lowest layer of this green roof system and, if necessary, drained away. The Retention Roof is available in various designs, with a choice of four different vegetation blankets. Read more about the Retention Roof here.

Download technical drawings Retention Roof

Green roofs against flooding

Due to climate change, the intensity of rain showers is significantly increasing worldwide. Sewage systems are not always able to cope with the large quantities of rainwater. In recent years, rivers have increasingly burst their banks and flooded areas. The economic and environmental damage caused by this is often considerable. In order to be able to collect this large amount of stormwater, water retention and detention on roofs is becoming increasingly important, especially in urban areas where greenery has had to make room for roads and buildings.

Rainwater management in green citiesIllustration by Natasha de Sena, Wageningen Environmental Research