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Finnish project to identify solutions for flooding in cities


New generation of water-permeable surfacing materials to be developed

Extreme weather conditions will occur more often in the future because of climate change. In Northern Europe, this means an increasing trend of heavy rainfall, particularly during the autumn and winter months. Flooding causes problems in dense urban environments where the water often cannot penetrate into the ground and rainwater collection systems lack the capacity for large volumes of water. VTT Technical Research Centre of Finland is leading a project that is seeking to identify flood water management solutions suitable for northern conditions through development of surfacing materials, technical design, and other means.

As cities grow and become more densely populated, an increasing portion of their surface becomes covered by hard, impermeable materials, such as asphalt and concrete. Together with the increase in rainfall, hard surface materials make urban flood management more challenging. New environmental regulations also require municipalities to find new ways of reducing the environmental load caused by pollutants in runoff water.

The two-year project develops new kinds of water-permeable surface materials to facilitate flood water management. These new materials can replace traditional dense asphalt, concrete and stone surfaces and reduce the accumulation of rainwater in areas such as streets and plazas. Flooding can also be prevented by developing sub-base structures, such as aggregate, pipes, geotextiles and water storage tanks.

The CLASS project is partly funded by Tekes, the Finnish Funding Agency for Technology and Innovation. In addition to VTT, project participants include the cities of Helsinki, Espoo, Vantaa and Oulu, as well as 12 industrial partners and associations.

There is close cooperation with the parallel Swedish project that focuses on sustainable urban development of solutions for green and grey surfaces. This project is coordinated by CBI and financed by the Swedish Governmental Agency for Innovation Systems VINNOVA. There are 22 project partners.

In both projects, the Finnish and Swedish cities that participate in the projects plan to pilot the permeable materials developed in the project, as well as the sub-base and water management systems. 

Further information:

Project web page: