From the SUOMI Hloubětín residential area, not a single drop of rainwater enters the ordinary sewer – all of it soaks into the ground. A combination of solutions helps slow the runoff: reservoirs for accumulating water, infiltration strips along the roads separated by intermittent kerbs, floodplain meadows and a natural central lake. In addition, the developer restored the original meandering character of the neighbouring Rokytka River – arranging spits and gentle banks for convenient access for people and animals. The site also has a green courtyard with recently planted trees, which are watered thanks to underground drainage and runoff from the slope.
This residential complex with responsible rainwater management is the first project of such a scale in Prague. It proves that residential development can grow with attention to environmental quality and help reduce climate risks.
The path of adaptation
Positive impact
The main goal of SUOMI Hloubětín is to slow the outflow of water from the area. The developer achieved this thanks to a thoughtful combination of measures in the buildings, public spaces and the adjacent landscape through which a stream flows.
Slowing the flow of the Rokytka and retaining water within the complex helps soften the impact of drought and reduce the possible consequences of downpours and floods. The large amount of greenery cools the whole neighbourhood on hot summer days, while the water bodies and river meanders create a favourable environment for biodiversity. The riverside zone also serves as a natural place to relax.
How does it work?
The SUOMI Hloubětín residential area, together with the restored Rokytka River, occupies more than 9 hectares.
To retain water on the site, a so-called low-impact development system is used – a hydro-ecological system of area management that uses the natural cycles of vegetation. This approach not only fosters local biodiversity but also maximises the infiltration (absorption) of water into the soil. By slowing surface runoff, the system allows moisture to be distributed evenly across the landscape exactly where it is needed to nourish plants and aquifers, instead of being irretrievably lost through the sewer network. In most of the buildings, rainwater is collected in reservoirs and pumped for watering lawns. The reservoirs are located under the apartment buildings. Excess water from them flows through distribution pipes to infiltration zones – open shallow ditches – and from there the remainder reaches the central infiltration pond and overflows into the new meander of the Rokytka.
A similar principle applies to draining water from roads, pavements and squares. Thanks to intermittent kerbs, water from the hard surface flows into green ditches with trees, connected to each other by underground gravel layers, pipes and gutters. This provides watering for the trees further down the slope. The water then gradually flows onto the infiltration floodplain meadows, and then into the central lake, where every drop of rain that has fallen on the complex’s territory ultimately ends up.
Thanks to the low-impact development system, it was possible to slow the outflow of rainwater as much as possible and reduce its inflow into the ordinary sewer to about 26 l/s from the entire area.
The first stage was designed by the firm ABM architekti s.r.o., stages 2–9 by Loxia Architects Ingenierie s.r.o., and the design documentation was developed by the company Němec Polák, spol. s.r.o.
The starting situation
On the site of today’s complex there was previously an abandoned industrial zone, overgrown with old trees, where waste was dumped illegally and homeless people lived. The Rokytka River was blocked between deep, neglected banks, and people had no access to it. The vegetation around was in poor condition.
Maintenance
The current costs of maintaining the facility are limited to standard care of the green plantings. Technical maintenance envisages that after about 10 years of operation, flushing of the geotextile filter may be required if it becomes silted, in order to restore the water permeability of the drainage system.
Why was this approach chosen?
The investor considered the possibility of draining the area using the usual method of laying sewer pipes. It was abandoned because of the strict limits on the maximum per-second runoff, and because such an approach contradicts the company’s environmental strategy.
Obstacles and challenges
No serious problems arose during implementation. However, the unexpectedly large volume of waste that had to be removed from the site did become a tangible challenge.
Operation
The investor faced unexpected resistance from operating organisations, which showed no willingness to take such a drainage system onto their books and maintain it. According to the investor, the market of management companies is not yet adapted to working with ecological engineering solutions.
How much did it cost?
The total cost of the project is 15 million Czech crowns, financed from the developer’s own funds. The expected payback and service life is 30 years.