Creating Sponge Cities

文献来源: Yu Kongjian, Felicia Toh. Creating Sponge Cities[J]. CUBES, 2018 MAY: 81-87

In Asia's rush towards urbanisation, a post-industrial framework of water management has largely been adopted.It is characterised by draining water away from our cities as quickly as possible, using pipes and concrete drains.Tropical Asian cities,however,unlike their European counterparts,are prone to sudden monsoonal downpours,leading to issues of flooding in cityscapes that areil equipped to deal with torrents of water.

Dr Yu Kongjian,founder and Principal Designer of Turenscape and Dean ofthe College of Architecture and Landscape Architecture at Peking University, presents the idea of Sponge Cities-a concept synthesising modern water management systems with the ancient Chinese agriculturalwisdom deployed in rice paddies and ponds. Sponge Cities retain and slow down the flow of water through the use of terraces,ponds and dykes. Urban landscapes become active systems that absorb excess water during monsoon rains,retain and filter it within a meandering landscape,and releaseit for use during dry seasons. The Sponge City solution to urban inundation has been applied in over two hundred cities in China and beyond, gaining credence as the Chinese government's adopted urban ecology framework.

Water-scarce Singapore certainly has reason to take a leaf or two out of Turenscape's book. China holds twenty per cent ofthe world's population, and yet only has access to eight per cent of global freshwater. Retaining water is thus a key national policy issue-a familiarrefrain in Singapore.When asked for his thoughts on Singapore's ecological development, DrYu raises several pertinent points."Singapore has built so much,allits rivers are channelised. Ramboll Atelier Dreiseitl did a great job with Bishan-Ang Mo Kio Park, but you have 100 more canals to deal with,"he jests. “There is strong bureaucracy and an established infrastructural framework-but if you can integrate an ecological mind set into the civil engineering system, Singapore can become a sponge nation, reachits goal of being self-sustainable,and solve the problem of floods,”he adds.

He shares four key strategies that are needed for Sponge Cities to work.Firstly,retaining water at its source.Turenscape was appointed in 2009 to solve the urban inundation problem in Harbin with the Qunli Stormwater Wetland Park project.Storm water is collected within the parkland using a pond-and-dyke system.Ash trees are planted along the periphery of the park, becoming a sponge band thatfilters rainwater before it flows into the central ponds, which are planted with native shrubs.A boardwalk above encircles the periphery, allowing people intimate access to nature. 

The second Sponge City strategy is slowing down water as it flows. “Streams should be meandering,not straightened.By slowing down a river, water can become productive, life-supporting and beautiful,"DrYushares.Turenscape's project Minghu Wetland Parkin Liupanshui beautifully illustrates the slowing down of water using pond terraces,creating inviting and fruitfulurban spaces that connect people with their city.

Living with water is the third strategy.“It's aboutadaptation. When waterturns into a flood it's too late-the water is too powerful then. Today, people depend on flood walls to protect cities. A better way to deal with wateris through Sponge Cities.The city adapts to the water instead,”Yu says.In Yanweizhou Park, a concrete flood wall was demolished and the landscape transformed into lush, brimming terraces accented by lightweight pedestrian bridges. The embankments are allowed to flood in response to the seasons, demonstrative of a pliant urbanism that coexists with waterinstead of barricading it with walls.

The fourth strategy is to clean the water using ecological means, as seen in Shanghai Houtan Park,where the polluted Huangpu river was remediated by Turenscape's interventions until it became safe for swimming.

Singapore will soon see an initial test bed of some of Dr Yu's strategies,as Turenscape was awarded noteworthy Rail Corridor commissions for the adaptive reuse of Tanjong Pagar Station and integrated housing at Choa Chu Kang with MKPLArchitects. Their proposals involve transforming the linear corridor into a social nexus that retains cultural heritage as well as ecologicalflows through the site.