Sponge Garden

Sponge concept and research

The climate is changing: the rain is heavier and the dry periods between are lasting longer. How can we moderate these two extremes? In urban environments rainwater currently drains through sewers to prevent flooding, but that also causes more drought. In the future there will be even a need for larger sewers, as the climate is changing.

Sponge city concept is about mitigating rainwater with nature-based solutions rather than larger underground sewers. Our research focused specifically of city of Rotterdam. By analysing the city’s geology, soils, climate, history and urban structure, we arrived to four characteristic sponge districts.

The mechanism the sponge principle itself, follows a threefold sequence of collecting water, storing it for a certain period and then returning the water into the ecosystem. This ‘Collect – Store – Return’ sequence implies that the concept of a sponge is in essence a system.

Sponge garden

In Sponge Garden we set out to test our research in practice. This garden is a test-site for simple and practical nature-based solutions to maximize water resources in the city during heavy rainfalls and periods of extreme drought while creating a context for enhancing biodiversity. In the garden three methods are being tested:

Soil cubicles – Rotterdam soils. Improving water retention of four characteristic Rotterdam districts. Low maintenance planting and effective soil enhancements for small areas like private gardens to encourage owners to contribute to climate measures and increase the overall amount of green spaces.

Waving wadi – capillary infiltration bioswale. It demonstrates how public space can be used to collect rainwater from a local catchment area of 4 to 5 times their size and to return their water slowly. These spaces can be effective for immediate buffering of heavy rainfalls. They subsequently retain the water for longer periods in order to be usable in extended periods of drought. It is divided in four subconcepts to offer diverse public use and aesthetics in urban contexts. A heavy rainfall was simulated on site and the bioswales absorbed all the rainwater in 30 min, proving that nature-based solutions can be perfectly suitable in preventing flooding in cities.

Depave garden – super infiltration. Immediate and simple ways to enlarge planted spaces and reduce the area of paved spaces. It is the most low-key intervention to depave hard infrastructure is being tested on its potential to function as a planter or even as a small garden.

The layout of Sponge garden follows the design of the Food garden (Voedseltuin) where planting is organised in circles. There is a meeting space in the middle of the Sponge garden and the outer doughnut is split in three parts, each dedicated to a different experiment. The garden is a pleasant collective space, well enjoyed by nearby office and Food garden workers, visitors and local residents. Educational and professional visits take place regularly.

The research and project is our own office initiative, in collaboration with municipality of Rotterdam and with support of Water boards, foundations and private parties. We planted and maintain the garden ourselves, together with Binder Groenprojecten.

Sponge Garden shows that designing flourishing public spaces can go hand in hand with researching new concepts for collecting, retaining and returning rainwater to the natural environment. It is an experimental garden where planting and maintenance is being adjusted over time. A simulation of heavy rainfall has been carried out and monitoring of soils and planting is taking place as well.

Our research focused specifically on the city of Rotterdam. In Sponge Garden we test out our research in practice. Here we have realized a test-site for simple and practical ‘natural’ solutions to maximize water resources in the city during heavy rainfalls and periods of extreme drought while creating a context for enhancing biodiversity. In the garden three methods are being tested – Soil cubicles, Waving wadi and Depave garden.
All manner of experiments are taking place in various beds in the circular garden with regard to soil mixtures, planting types and sponge techniques. For example, there are “wadis” (water run-off & drainage channels, man-made swales) with hop and water guzzling plants, Rotterdam clay and peaty soils with suitable garden vegetation and a softening garden (no paving) with plants that thrive in dry conditions.
Sponge garden is a showcase of public and private space projects that could be realized across the city. It demonstrates that a heavy rainfall can be easily solved with natural soil and planting solutions and without any need for underground sewage. In the garden experiments are being carried out with various soil compositions and suitable planting.

The process

In the past two years, the behavior of water and soil has been measured in the Sponge Garden. The performance of the vegetation planted has also been monitored. The results of the investigation are instructive and useful in practice and interesting to anyone working towards a city which adapts to the climate.

Why this project should be awarded
– Sponge garden is a showcase of public and private space projects that could be realized across the city. It demonstrates that the cons of a heavy rainfall can be easily solved with natural soil and planting solutions and without any need for underground sewage. In the garden experiments are being carried out with various soil compositions and suitable planting.
– Sponge Garden shows that designing flourishing public spaces can go hand in hand with researching new concepts for collecting, retaining and returning rainwater to the natural environment. It is an experimental garden where planting and maintenance is being adjusted over time and extreme rainfalls are simulated.

Introduction

De Urbanisten is a Rotterdam based office for urban design and landscape architecture and intrigued by the challenges that the modern world provides us. Climate change and the rapidly changing world challenge us to look at our social functions, living environments and public spaces in a new and bold way. This era calls for urban structures and public design changes that emphasize the importance of creating space for a biodiverse company of people, plants, and animals. We specifically want to contribute to both a sustainable and attractive living environment for people and other earthlings. Therefore, a strong focus on climate adaptation and ecology can be found in all of our projects.

The municipality of Rotterdam is already tackling these problems by applying smart measures like water squares, bioswales and more open water. However, a lot still remains to be done; the city of Rotterdam is predominantly paved and the greenery that has been planted is hardly suitable to mitigate the two extremes of rain and drought.

Design year: 2018
Year Built: 2018 – 2019

Location | Keilestraat 5, 3029 BP Rotterdam, The Netherlands
Sponsors and Support | Water Sensitive Rotterdam, Stichting Voedseltuin Rotterdam, Gemeente Rotterdam, Hoogheemraadschap Delfland, Provincie Zuid-Holland, EFL Stichting, Binder Groenprojecten, Kim Kogelman, Lapinus
Collaboration | Municipality of Rotterdam, Stichting Voedseltuin Rotterdam

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