Foto: SUOMI Hloubětín, YIT Stavo s.r.o., Petr Andrlík
Rainwater management in SUOMI Hloubětín
Not a drop of rainwater flows from the SUOMI Hloubětín residential area into the classic sewer. It seeps directly into the ground. The outflow of rainwater from the area is slowed down by means of retention tanks, infiltration rigs around the roads lined with intermittent curbs, flooding infiltration meadows and a nature-like central lake. In addition, the investor restored the original meandering character of the nearby river Rokytka, with point bars and shallow slopes for better access for people and animals. There is also a green courtyard and newly planted trees, which are irrigated using an underground drainage system and a runoff water from the slope.
The development project of a residential area with responsible rainwater management is the first project of such a scale in the City of Prague. It is an example of the fact that housing development can also be conducted with an emphasis on the quality of the environment and can contribute to minimizing climate risks.
The Adaptation Journey
The positive impact
The main goal of the SUOMI Hloubětín project is to slow down the outflow of water from the area to 3 l / s / ha. The investor achieved this goal by a sophisticated combination of various measures both in the buildings and in the public space and in the neighbouring landscape through which the stream flows.
Slowing down the water in Rokytka and water retention in the SUOMI Hloubětín complex helps to reduce the effects of drought and limit the possible effects of torrential rains and floods. Thanks to the large amount of green spaces, the whole area cools down during summer heat waves and in addition, the bodies of water and meanders on the river are a great place for biodiversity. The surroundings of the river serve, among other things, as a natural space for recreation.
How does it work?
The residential district of SUOMI Hloubětín, which includes the revived river Rokytka, covers an area of more than 9 hectares.
A system of so-called low impact development, ie hydroecological management of the area using natural vegetation cycles, is used to retain water in the area. The system helps increase biodiversity, maximizes infiltration, slows down water flow, and helps water spread and seep where it is needed, instead of draining it from the landscape.
Rainwater in most houses is collected in retention tanks and pumped to water common grass areas. Retention tanks are located under apartment buildings. Excess water from the sumps then flows through the distribution pipes outside to the infiltration areas, open shallow ditches with the infiltration function and only then the rest of the water reaches the central infiltration pond and from there overflow to the newly meandering river Rokytka.
The system is similar for drainage of public roads, pavements and squares. Thanks to the intermittent curbs, the paved areas lead the rainwater into the green ditches with trees, which are interconnected by underground gravel cushions, pipes and chutes. They provide watering of trees down the slope. Rainwater is thus again gradually drained into the infiltrating flooding meadows and then into the central infiltration lake, where in the end every drop of rainwater from the housing estate ends.
By using the so called low impact development system, they reached the maximum slowdown of rainwater runoff from the area and reduced the water flowing from the built-up area into the ordinary sewerage to the level of approximately 26 l / s from the whole area.
The author of the 1st stage is ABM architekti s.r.o., the author of stages 2 – 9 is Loxia Architectes Ingenierie s.r.o., the author of the project documents of most stages is Němec Polák, spol. s.r.o.
In the place where the residential area now stands, there was a brownfield overgrown with old trees, which was used for illegal landfills and where homeless people lived. The Rokytka River was regulated with deep neglected banks and people could not access it. The surrounding vegetation was in poor condition.
Operation and maintenance
Running costs consist of the maintenance of green surfaces and in about 10 years, if the filter fabric becomes clogged, the backfilling should be washed out.
Why was the measure chosen?
The investor considered the option of draining the area using the usual method of sewerage pipes. The company did not choose this alternative due to the need to comply with the maximum outflow limit per second and also because it is in conflict with the company's current strategy.
Obstacles and challenges
There were no major issues during the implementation. However, the unexpected amount of waste that had to be removed from the site was certainly a challenge.
Operation and maintenance
The investor did not expect such great resistance from facility management companies to take over the drainage system. According to the investor, the companies are not ready to deal with an ecological solution.
How much did it cost?
The total cost of the project was 15 million CZK. The implementation of the project was financed by the investor from the company’s own resources.
The investor expects a return on investment in 30 years. The expected life of the investment is also 30 years.
Family and apartment houses Urban greenery Use of rainwater Lack of water and drought