New solution for cloudburst protection of large buildings

The increasing risk of floods caused by climate change has led municipalities to search for new solutions for handling growing volumes of water. COWI and Grundfos has engineered a new, economical and space-saving bypass pump well serving this purpose.


A recently engineered bypass pump well will help protect large buildings and companies from floods and meet the growing demand for climate-proofing measures with municipalities and companies in Denmark.

”A bypass pump well is an economical and space-saving alternative to rainwater basins, which have grown in number as cloudbursts have become more frequent. In particular in cities, basins pose challenges since they require space, which is not always available,” says Project Manager Jesper Valentin Nielsen, COWI.

In case of a cloudburst, the newly developed engineered pump well goes into action, protecting the structure from water penetrating the basement as well as backflow from the sewer network. This presents new possibilities of protecting, e.g., large company premises, schools and housing associations in densely built areas, without interrupting the water supply. So far, the solution has been implemented on a school and a large data central in Copenhagen.

From 2-3 litres to 120 litres a second

The pump was inspired by similar solutions applied in single-family houses, which combine a backwater device and a well, from where rainwater under pressure is pumped into the sewer system. As a result, you do not have to turn off the water after a flood, and to a higher extent, the operation of schools, companies and, for instance, housing associations will be able to continue unaffected by cloudbursts.

The model designed for single-family houses handles 2-3 litres a second, whereas the newly engineered pump well handles around 120 litres of water a second.

”In principle, we've developed a solution that can be expanded to handle ever larger volumes of water, if that's relevant. It may seem like a relatively costly solution, but not if you consider the costs of the damage caused by, e.g., repeated floods at Lergravparkens School in Amager,” explains Nielsen.

Orthophotos of previous floods

The solution calls for quite precise information about the volumes that the well and pumps are to handle. To be able to provide that, you need information about the conditions on site and how the flood develops, explains Klaus Gerhard Hansen, Grundfos:

”In this regard, COWI has proven a strong partner because not only are they experts in flood protection of buildings; They are also able to calculate how and how much a flood will develop in a specific location,” he says.

Get in contact

COWI employee Søren Kragh Pedersen

Søren Kragh Pedersen
Head of Group PA & PR
Communication, Denmark

Tel: +45 2025 7018