In Europe’s major cities, at least in their historic districts, an ageing, combined sewer network, like in Budapest, is used to drain rainwater collected in public areas and ultimately discharged into the sewerage system. However, this system is no longer able to cope with the increased volume of water caused by intensive urbanisation and increasingly heavy rainfall. Not only there no money to rebuild it, but there is no space, with an incredibly complex network of utilities beneath our feet.

In his article published in Albert Földgömb magazine, Ferenc Szigeti not only traces the emblematic European examples of the sponge city concept that has become key in recent years, but also shows how the development of Budapest municipalities participating in the LIFE in Runoff project is turning the previously problematic rainfall into an asset in Hungary.

“In Berlin, for example, entire city blocks are being built to contain water like sponges, protecting utilities not designed for flooding. The building has green roofs and green walls, with rain gardens and percolators in between, to retain or delay water run-off, and the pavement allows a significant amount of water to pass through.” shares his experience Zoltán Rózsa, head of the Green Office of the Hegyvidék Municipality.

One of the pride of Copenhagen is the Tåsinge Square in the city centre, where cars parked on the tarmac have given way to a carefully designed chain of rain gardens with a drainage system that not only collects a significant amount of rainwater run-off from the surrounding houses, but also acts as a resting place. Sure, it’s easy in Copenhagen, home of the co-operative movement and known for its cycling culture, but at home it’s anything but – we often say. But we have been using this card as an excuse for decades, when we know very well that Denmark started almost exactly the same way decades ago, and Copenhagen does not hide the fact that the negotiation process for Tåsinge Square was very difficult.

A catchment area in the city, or: where urban rain is already valued and treated as an asset in Hungary

At the start of the LIFE in Runoff Programme 2021, it was not even clear who could design a rain garden in Hungary, nor were responsibilities and regulations clear.

Due to its topography, in the 12th district the problem of the regular flooding of Győri út in the Buda hills of the Buda district was originally thought to be solved by a large underground cistern. But preliminary studies showed that a problem does not necessarily have to be tackled where it occurs: for example, in the urban jungle, where utilities make it difficult to plant even a single a tree, let alone sink a huge cistern underground… Moreover, several, smaller solutions can often be more effective in tackling a problem.

Modelling water run-off in urban environments is incredibly complex, as essentially every roadway and sewer network has to be taken into account. 12. district was divided into catchment areas for better planning, which showed that flooding on the Győr road, which is often experienced, should be tackled at the top of the hill, on Sváb Hill. “We wanted to capture rainwater from the roof of the impressive building of the Mór Jókai Elementary and German Nationality School and the neighbouring church by creating underground reservoirs and a rain garden. The designers of the experimental rain garden at Pünkösdfürdő Park, which was built using a gravel water retention layer, did not take on the implementation precisely because of its experimental nature, so we found an American Hungarian landscape architect who designed the rain garden using the Seattle method (where a humus layer retains water very effectively)” – Zoltán Rózsa explains the bumpy road to implementation.

But the reality came to light: it turned out that the school’s machinery really needs the rainwater to flush the sewers occasionally to avoid blockages, and the Municipality could not reach an agreement with the church on ownership issues. Finally, the municipality will build a three-element, modular, expandable, underground reservoir in the vicinity, the water from which will be used to irrigate small green areas.

In the 18. district although no detailed drainage study has been carried out, the problematic road sections have been mapped and the municipality has identified the most problematic location for intervention.

Subsurface seeps, wooded ditches with water retention medium and rain gardens will all seep water here, if only because, contrary to foreign practice, the Metropolitan Sewerage Works does not allow the overflow of rain gardens to be connected to the network.

Cover photo by István Kissimon