China’s ‘sponge cities’ aim to re-use 70% of rainwater. Here’s how they do it

The Sino-Singapore Tianjin Eco-city in Tianjin Binhai New Area, China. Image: EPA.

Asian cities are struggling to accommodate rapid urban migration, and development is encroaching on flood-prone areas. Recent flooding in Mumbai was blamed in part on unregulated developmentof wetlands, while hastily built urban areas are being affected by flooding across India, Nepal, and Bangladesh.

This is not a trend only in developing countries; floods in Houston, USA, highlighted the risks of development in environmentally sensitive and low-lying areas. In 2012, a severe flood in Beijing wreaked havoc on the city’s transportation systems, and in 2016 floods overwhelmed drainage systems in Wuhan, Nanjing, and Tianjin. The challenges are clear.

Groundwater over-extraction, waterway degradation, and urban flooding are forcing China’s cities to address a vicious cycle. Sprawling urban development and use of impervious material prevent soil from absorbing rainwater, prompting further investment in infrastructures that typically impede natural processes and worsen flood impacts.

China’s “sponge city initiative” aims to arrest this cycle through the use of permeable surfaces and green infrastructures. However, the initiative faces two challenges: lack of expertise of local governments to effectively coordinate and integrate such a complex set of activities, and financial constraints.


The concept

Engineering solutions are popular interventions, but cities cannot simply pipe away flood risks. To address the issue, China’s sponge city initiative has an ambitious goal: by 2020, 80 per cent of urban areas should absorb and re-use at least 70 per cent of rainwater.

Launched in 2015 in 16 cities, the initiative seeks to reduce the intensity of rainwater runoff by enhancing and distributing absorption capacities more evenly across targeted areas. The resulting groundwater replenishment increases availability of water for various uses. This approach not only reduces flooding but also enhances water supply security.

The initiative is similar to the North American concept of low-impact development (LID), which according to the United States Environmental Protection Agency (EPA) mimics natural processes in order to protect water quality.

The case of Lingang, a planned city in Shanghai’s Pudong district, illustrates typical sponge city measures. These include rooftops covered by plants, scenic wetlands for rainwater storage, and permeable pavements that store excess runoff water and allow evaporation for temperature moderation.

With ambitions to be China’s largest sponge city project, the Lingang city government has invested $119m in retrofits and innovations that could be a model for the majority of Chinese cities lacking modern water infrastructure.

Chinese cities are making noteworthy efforts. In a pledge to expand coverage of urban greenery, Shanghai announced in early 2016 the construction of 400,000m2 of rooftop gardens. The project is a collaborative effort among city regulators, property owners, and engineers. Sponge city projects in Xiamen and Wuhan have performed effectively during heavy rainfall.

Grassy rooftops in Shanghai. Image: kafka4prez/Flickr/creative commons.

Improved policies and budgets

The sponge city initiative requires a holistic and sustained effort, including effective environmental governance. However, concerns persist about weak regulations and selective enforcement. Local officials cannot simply turn the other way when violations are discovered. The unsung tedium of tightening controls is less exciting than bold innovations, but equally crucial for managing water. Gains from sponge city programs should not be offset by poor environmental governance.

Funding is also a persistent constraint. To date, more than $12bn has been spent on all sponge city projects. The central government funds roughly 15-20 per cent of costs, with the remainder split between local governments and the private sector.

Unfortunately, the initiative coincides with a burgeoning municipal debt crisis spurred in part by restrictive financial reforms, bond ratings cuts, and nervous bond markets. China’s cities may soon find borrowing costs even higher and avenues for reducing debts narrower.

Investment in sponge city initiatives is also proving to be an increasingly difficult sell, with only tepid interest from domestic private investors. The government should improve conditions that encourage investment, including tax incentives, better project transparency, and looser credit markets.

Until this happens, sponge city initiatives will have to compete against visible and familiar infrastructure such as roads, transit, and utilities. They will also have to be attractive in a market with numerous other investment options.

Innovative water initiatives have been adopted worldwide, including wetland restoration in the American Midwest, flushing systems using collected rooftop water in Oregon USA, bioswales in Singapore, and public spaces as flexible water retention facilities in the Netherlands.

The ConversationChina has an opportunity to strengthen its emerging global leadership role in urban sustainability. However, it must first implement an effective vision for how sponge city initiatives complement broader environmental governance efforts. Improving regulatory enforcement and reviving interest in related private investment opportunities are two steps it can take.

Asit K. Biswas is a visiting professor at the Lee Kuan Yew School of Public Policy, National University of Singapore. Kris Hartley is a lecturer in city and regional planning at Cornell University.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

Was the decline in Liverpool’s historic population really that unusual?

A view of Liverpool from Birkenhead. Image: Getty.

It is often reported that Liverpool’s population halved after the 1930s. But is this true? Or is it a myth?

Often, it’s simply assumed that it’s true. The end. Indeed, proud Londoner Lord Adonis – a leading proponent of the Liverpool-bypassing High Speed 2 railway, current chair of the National Infrastructure Commission, and generally a very influential person – stood on the stairs in Liverpool Town Hall in 2011 and said:

“The population of Liverpool has nearly halved in the last 50 years.”

This raises two questions. Firstly, did the population of the City of Liverpool really nearly halve in the 50 year period to 2011? That’s easy to check using this University of Portsmouth website – so I did just that (even though I knew he was wrong anyway). In 2011, the population of the City of Liverpool was 466,415. Fifty years earlier, in 1961, it was 737,637, which equates to a 37 per cent drop. Oops!

In fact, the City of Liverpool’s peak population was recorded in the 1931 Census as 846,302. Its lowest subsequent figure was recorded in the 2001 Census as 439,428 – which represents a 48 per cent decline from the peak population, over a 70 year period.

Compare this to the population figures for the similarly sized City of Manchester. Its peak population also recorded in the 1931 Census as 748,729, and its lowest subsequent figure was also recorded in the 2001 Census, as 392,830. This also represents a 48 per cent decline from the peak population, over the same 70 year period.

So, as can be seen here, Liverpool is not a special case at all. Which makes me wonder why it is often singled out or portrayed as exceptional in this regard, in the media and, indeed, by some badly briefed politicians. Even London has a similar story to tell, and it is told rather well in this recent article by a Londoner, for the Museum of London. (Editor’s note: It’s one of mine.)

This leads me onto the second question: where have all those people gone: London? The Moon? Mars?

Well, it turns out that the answer is bit boring and obvious actually: after World War 2, lots of people moved to the suburbs. You know: cars, commuter trains, slum clearance, the Blitz, all that stuff. In other words, Liverpool is just like many other places: after the war, this country experienced a depopulation bonanza.


So what form did this movement to the suburbs take, as far as Liverpool was concerned? Well, people moved and were moved to the suburbs of Greater Liverpool, in what are now the outer boroughs of the city region: Halton, Knowsley, St Helens, Sefton, Wirral. Others moved further, to Cheshire West & Chester, West Lancashire, Warrington, even nearby North Wales, as previously discussed here.

In common with many cities, indeed, Liverpool City Council actually built and owned large several ‘New Town’ council estates, to which they moved tens of thousands of people to from Liverpool’s inner districts: Winsford in Cheshire West (where comedian John Bishop grew up), Runcorn in Halton (where comedian John Bishop also grew up), Skelmersdale in West Lancashire, Kirkby in Knowsley. There is nothing unique or sinister here about Liverpool (apart from comedian John Bishop). This was common practice across the country – Indeed, it was central government policy – and resulted in about 160,000 people being ‘removed’ from the Liverpool local authority area.

Many other people also moved to the nearby suburbs of Greater Liverpool to private housing – another trend reflected across the country. It’s worth acknowledging, however, that cities across the world are subject to a level of ‘churn’ in population, whereby many people move out and many people move in, over time, too.

So how did those prominent images of derelict streets in the inner-city part of the City of Liverpool local authority area come about? For that, you have to blame the last Labour government’s over-zealous ‘Housing Market Renewal Initiative’ (HMRI) disaster – and the over enthusiastic participation of the then-Lib Dem controlled city council. On the promise of ‘free’ money from central government, the latter removed hundreds of people from their homes with a view to demolishing the Victorian terraces, and building new replacements. Many of these houses, in truth, were already fully modernised, owner-occupied houses within viable and longstanding communities, as can be seen here in Voelas Street, one of the famous Welsh Streets of Liverpool:

Voelas Street before HMRI implementation. Image: WelshStreets.co.uk.

The same picture after HMRI implementation Image: WelshStreets.co.uk. 

Nonetheless: the council bought the houses and ‘tinned them up’ ready for demolition. Then the coalition Conservative/Lib Dem government, elected in 2010, pulled the plug on the scheme. 

Fast forward to 2017 and many of the condemned houses have been renovated, in a process which is still ongoing. These are over-subscribed when they come to market, suggesting that the idea was never appropriate for Liverpool on that scale. 

At any rate, it turns out that the Liverpool metropolitan population is pretty much the same as it was at its peak in 1931 (depending where the local borough boundaries are arbitrarily drawn). It just begs the question: why are well educated and supposedly clever people misrepresenting the Liverpool metropolis, in particular, in this way so often? Surely they aren’t stupid are they?


And why are some people so determined to always isolate the City of Liverpool from its hinterland, while London is always described in terms of its whole urban area? It just confuses and undermines what would otherwise often be worthwhile comparisons and discussions. Or, to put it another way: “never, ever, compare apples with larger urban zones”.

In a recent Channel 4 documentary, for example, the well-known and respected journalist Michael Burke directly compared the forecast population growths, by 2039, of the City of Liverpool single local authority area against that of the combined 33 local authority areas of Greater London: 42,722 versus 2.187,708. I mean, what bizarre point is such an inappropriate comparison even trying to make? It is like comparing the projected growth of a normal sized-person’s head with the projected growth of the whole of an obese person, over a protracted period.

Having said all that, there is an important sensible conversation to be had as to why the populations of the Greater Liverpool metropolis and others haven’t grown as fast as maybe should have been the case, whilst, in recent times, the Greater London population has been burgeoning. But constantly pitching it as some sort of rare local apocalypse helps no one.

Dave Mail has declared himself CityMetric’s Liverpool City Region correspondent. He will be updating us on the brave new world of Liverpool City Region, mostly monthly, in ‘E-mail from Liverpool City Region’ and he is on twitter @davemail2017.