As a country with a major problem with urban flooding, China has been working hard over recent years to implement innovative flood defence and drainage strategies to tackle the perennial and recurrent issue of devastating floods that it faces every single year.
Its solution to the problem? The development of sponge cities – an idea that has been floating around Europe and the rest of the world for decades.
It’s a simple concept based on incorporating more permeable materials and green spaces into the development of cities to help soak up rainfall and ensure the effective run off of water away from flooded areas.
While sponge cities are a somewhat new strategy in China, in Europe, such Sustainable Urban Drainage Systems (SUDS) have been integrated into designs for years. But, while we may be pioneers in sustainable drainage solutions, it’s safe to say that no one has embraced the use of sponge cities quite as enthusiastically as China, nor utilised them on such an extensive scale.
It makes sense that China should have SUDS on steroids when you consider that the country is grappling with compromising typography, massive population growth, rapid urbanisation and poor water management, which all exacerbate its problems. Clearly, China needs a little more help than we do, but could we learn anything from the country’s now huge emphasis on SUDS?
The truth is, China’s sophisticated and rapid adoption of sponge cities on a huge scale draws interesting questions of whether the UK should also consider implementing more developed SUDS solutions, rather than viewing them as a secondary after thought.
There is a case to be made – SUDS can be an effective and sustainable way of managing surface water in the urban environment. Urbanisation reduces the amount of rainfall that can soak away into the ground, therefore SUDS and their absorbent qualities help manage the rainfall to prevent flooding.
With more intense storms and rain predicted in the future, and with towns and the density of developments continuing to increase, perhaps SUDS could provide a possible solution to the subsequent rising volumes of surface water that our piped drainage systems will need to cope with.
SUDS components work in several ways: they can soak water into the ground, flow into a watercourse, provide storage as well as slow down flows of water.
There are a number of ways that SUDS could be incorporated into future infrastructure including:
- Green roofs – This approach sees the roofs of buildings and structures such as office blocks covered with vegetation and landscaping which helps to filter water into a drainage area below.
- Permeable paving – This form of pedestrian paving allows rainwater to infiltrate through the surface into underlying layers so that water can be temporarily stored before infiltration to the ground, reused, or discharged.
- Swales – These shallow, broad and vegetated channels are incorporated into ground landscaping to store and convey runoff and remove pollutants.
- Filter trenches – Infiltration trenches are shallow excavations with rubble or stone that can easily be included into landscaping to create temporary sub-surface storage for storm water runoff, improving natural drainage.
The great thing about SUDS is that, as well as helping to reduce flooding, this approach also enhances water supply security by collecting, storing and cleaning groundwater for various uses.
Unsurprisingly, councils across the country are choosing to incorporate sponge city concepts into their existing building and development programs.
But SUDS should be just that – additions, as opposed to alternatives, to conventional drainage solutions.
While they certainly have their benefits, SUDS alone simply will not cut it when there is excessive and unprecedented rainfall. However, used in in tandem with heavy machinery solutions, they can provide a cost-effective way of adding additional capacity and flexibility to our existing water drainage systems.
With cities getting bigger and climate change threatening to bring more extreme weather, it may be time to seriously consider sponge cities and a reimagination of the urban landscape to ease the growing demand on our existing systems and create an environment where water can not only be captured and controlled, but also effectively re-used.