Sponge Research
De Urbanisten: 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 on the city of Rotterdam. By analyzing the city’s geology, soils, climate, history, and urban structure, we identified 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 applied our research in a practical setting. This garden is a test-site for simple and hands-on 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. 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. In the garden three methods are being tested:
Soil cubicles – Rotterdam soils. Improving water retention in four characteristic Rotterdam districts: peat, clay, sand, and rubble mix. 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 utilized to collect rainwater from a local catchment area that is 4 to 5 times its size and to slowly replenish the water. These spaces can be effective for immediately buffering heavy rainfall. They subsequently retain the water for longer periods to make it usable during extended periods of drought. It is divided into four sub-concepts 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 minutes, proving that nature-based solutions can be perfectly suitable in preventing flooding in cities.
Depaved garden – super infiltration. Easy and immediate ways to expand planted areas, create planters, or a small garden, while also reducing paved surfaces. This is the most low-key intervention to remove hard infrastructure, for example, along roads across the city.
The layout of the 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 into three parts, each dedicated to a different experiment. The garden is a pleasant communal space, enjoyed by our office, nearby offices, food garden workers, visitors, and local residents. Educational and professional visits guided by our own team take place regularly.
The research and project are our own office initiative, in collaboration with the municipality of Rotterdam and with the support of Water boards, foundations, and private parties. We planted and maintain the garden ourselves.
Landscape architecture: De Urbanisten
Year completed: 2019
Photo credits: De Urbanisten
