What is the "sponge city" concept that utilizes natural rain water to lower the temperature in urban areas?

A phenomenon in which the temperature becomes higher as compared with the urban area than in the suburbs is called "Heat island phenomenon"Although it is called" asphalt, which is considered to be the main cause and concrete "Sponge CityIt is said that the concept is adopted in urban development in Berlin, Germany.

Berlin is Becoming a Sponge City - YouTube


In cities with many buildings such as skyscrapers, there are many artifacts made of concrete, glass and steel.


Artifacts absorb heat ... ...


In order to repel water, "hot bill" and "reflection" will make hot summer feel more hot.


An unusual approach has started in a city in Germany against such thermal problems in urban areas.


That approach is a "sponge city" initiative that makes good use of rainwater.


The basic idea in "Sponge City" is to "keep rain water in urban areas". Why leave the rain water, as the water evaporates, the surroundings will cool accordingly.


Carlo Becker, an architect who is involved in Berlin's "Sponge City" initiative, says, "For us, rainwater is not just a resource to shed anywhere else but to leave it in the city."


In the natural environment, rainwater will soak into the ground and plants ......


Most of it evaporates. It is said that the surroundings are felt cool by evaporation of much moisture.


However, in urban areas, the ground down and buildings are covered with concrete and glass, so the cool down system due to natural environment is collapsing. Most of the water can not penetrate into concrete, and it is the current situation in urban areas that it is carried to another place by traveling through a pipe.


On the other hand, in the "Sponge City" concept, we try to reduce the temperature in urban areas by imitating rainwater circulation in the natural environment by leaving rainwater on the ground. How to leave water in the urban area is to cover the surface of the building with green and dig the trench to the side of the road so that it can store rainwater.


This makes it possible to keep more moisture than ordinary cities and to lower the urban temperature.


RUN MELSBURG in the eastern part of Berlin has been a large-scale case of "Sponge City" initiative 20 years ago.


"The green roof is extended to 6 to 8 cm thick, and the water flow is directed towards the courtyard in the middle," said Hiko Seeker, a city hydrologist.


Mr. Seeker talks about how the Sponge City concept is adopted in a U-shaped building like the following.


"There is a garage under the courtyard in the middle of the building and there is a layer of soil of about 80 cm between the ground and the garage The layer of this soil is like a sponge and pours into the building even in heavy rain Plants use the water sucked up by the soil and eventually all the water evaporates, "sheika said.


Furthermore, a small groove is dug in the side of the road, and it is designed so that rain water rushed down to the ground flows.


Seeker says about the city of Rungmersburg, which took in the sponge city concept, "When it's hot summer day, this place will feel really cool compared to other urban areas, because the moisture is evaporating , This may be called 'natural air conditioner'. "


Rung Melsburg is one example of the sponge city initiative, and it seems that there are compartments built under similar concepts in other parts of Berlin.


However, Berlin is not a perfect sponge city. In the middle of the summer of 2017, the greatest heavy rain in the history of the past 110 years attacked Berlin, flooding damage occurred in many places.


"We need not only to understand climate adaptation measures for cities but also to implement them, which requires a political will to do," Becker said.


In Berlin's local council, it is decided to introduce a new facility that inherited the sponge city initiative to counter the heavy rainfall.