字幕表 動画を再生する 英語字幕をプリント Cities are concrete, glass and steel - they look and act un-naturally - absorbing heat and repelling water. Our urban spaces are at odds with the natural environment. But, in parts of the German capital things are different. To deal with rainwater and heat, Berlin is being transformed into what’s called a Sponge City Carlo Becker is the architect of Berlin’s Sponge City strategy… which harnesses rainwater and manages heat. In a natural ecosystem, rainwater is soaked up by soil and vegetation, the majority then evaporates and the rest filters deeper into the ground. The evaporating water then cools the surroundings. Cities disrupt this system. Water can’t soak through the concrete and is piped away. The Sponge City strategy aims to keep rainwater where it lands, to imitate the natural water cycle. Buildings are covered in green roofs and facades. And down on street-level, urban wetlands and road-side trenches - known as Swales - filter run-off and hold water, keeping the city cool by imitating nature. This is Rummelsburg, in East Berlin. Built 20 years ago, it’s become a large scale example of the Sponge City concept. On top we have extensive green roof of approximately 6 to 8 cm and from there the water flows into these courtyards here in the middle, and underneath there is a garage. On top of the underground garage we have a soil layer of almost 80 cm. It’s like a sponge and it soaks the water during heavy rainfall and then it's used by the plants... so they take all the water and finally evaporate it. Heiko Sieker is the brains behind the neighborhood’s innovative management of stormwater. In the whole area here we have no storm sewer system, so no conventional pipe system. The water flows from the road surface into the swale and from here it’s infiltrating into the ground. On hot summer days, you can really feel the coolness here, it’s much cooler compared to other parts of the city because of the evaporation. You can say it’s natural air-conditioning. Rummelsburg is just one example of a Sponge City - neighbourhoods across Berlin have implemented similar initiatives. But Berlin isn't a perfect Sponge City. In the middle of summer 2017 the heaviest rain in the century hit the city submerging parts under water and warning how much work there's still to do. In fact, the city council has recently decided all new developments should manage stormwater on site, in the spirit of the Sponge City. Climate Change is forcing Berlin and many other cities around the world to adapt urban environments... transforming them to work with nature, not against it.