By 2025 Hangzhou is likely to become one of China’s mega-cities with a population of more than 12 million people. The sheer size of the city will stimulate extraordinary economic activity but the available urban planning models seem unable to deliver either highly livable, or environmentally sustainable cities.
A New Model
Symbiotic City is a new planning model which combines nature and the city in a symbiotic relationship of mutual benefit. The model provides a framework for an environmentally sustainable city: minimising energy use and harnessing renewable energy on site; managing and reusing waste on site; producing a portion of the city’s food on site; harvesting, minimising use, and reusing the city’s water on site.
Symbiotic City is created by laying an urban network over a rural network. The bands that make up the urban networks are never more than 1.6 kilometers wide, while the bands that make up the rural network are never less than 1.6 kilometers wide. This means that even in the centre of the urban band, symbiotic city’s citizens are never more than 800 meters (a ten-minute walk) away from large areas of rural open space offering a diversity of ecological, active, and productive programs. These productive landscapes will contribute to feeding the citizens of symbiotic city and, being close to the population, ensure the CO2 emissions generated by transporting food to the populace are kept to a minimum.
The consequence of the intersection of these continuous networks is that a rhythm of purely urban cells and purely rural cells are interspersed with hybrid cells – cells that are both urban and rural. These hybrid cells can be configured to allow the urban experience to be continuous or the rural experience to be continuous in either direction. These hybrid cells also accommodate a series of eco-corridors that form another network connecting all the purely rural cells. These purely rural cells act as cool sinks within the urban environment, easing the urban island heating effect and cooling the southerly summer winds. They are also a rich source of oxygen located adjacent to the dense urban cells.
Vehicles dominate urban environments because roads are the only continuous systemized surface network in cities. Other systems may at best be tree-like structures, but are only connected to the road network, not directly to each other. Symbiotic city doesn’t privilege the road as the only continuously linked network – the existence of a number of equally important high quality networks ensure the urban environment offers a series of alternative and continuous other ways of experiencing the city. These networks also provide the physical continuity and connection of the various programs of the city’s complex 21st Century economic, social and cultural activity.
Fractal Community Structure
Access to public transport is the basis of the community structure – a 400m radius transport oriented development. At this scale of the city, the community is provided with public transport within a five-minute walk of an urban plaza and public parkland. Each of the transport oriented developments are split into four neighbourhoods (each having a 200m radius) each with their own plaza and parkland. These neighbourhoods are in turn split into four 100m radius mosaics of subculture – smaller scale urban places where the various cultures that exist in the community (the elderly, school children, farmers, youth, etc.) have the opportunity to use the plaza and pocket park regularly. At the larger scale, four of the transport oriented developments combine to become the 1.6 kilometer-wide wide city bands. Again, at this scale, the city is provided with a major urban plaza and parkland. Importantly all these open spaces (both plaza and park) are linked to each other with either the hard or soft networks that run through the city network. They also connect to the rural network.
Each of these fractal community structures have their centers or nuclei – the urban plaza – located, not in the centre of the community, but off-centre, towards the next biggest nucleus. This is a strategy to reduce the use of the car within local transport areas. With an off-centre nucleus, a large majority of symbiotic city citizens who walk to their sub-cultural or local shopping area are also on their way to the neighbourhood shopping area. In fact they are also on their way to the nucleus of their local transport area. If what they need is not at their local shops, they are more likely to continue walking to the next nucleus than return home to get their car and then drive to the next larger nucleus.
Zoning and Programs with Flexibility
The logical evolution of the history of land use zoning, continuous intersecting networks of the various land uses, are spread through the city. Retail and commerce are directly attached to the light rail public transport system. Housing is the next network, followed by the high-tech industry, research and development network. This places housing in between these two major sources of employment and close to the public transport system. Like the other networks in the city, these networks regularly intersect with each other forming hybrid zones which provide the opportunity for mixed use – housing with retail and office; high-tech/R+D with retail; housing with high -tech/R+D, etc. Importantly, these hybrid also provide the city with significant areas of flexibility where unpredictable future demand can be accommodated. Within these continuous and flexible land use zones, a multiplicity of urban programs and their combinations are provided. Also, given the fractal community structure is focused on hard and soft public open spaces, various sites adjacent to these fractal open spaces become the sites for various public building programs. In addition to these sites, the active rural cells provide locations for a variety of public health and well being programs, like hospitals, health-care centers, and physical education facilities.
Sustainable Forms of Transport
The emphasis in symbiotic city is on sustainable forms of transport – public transport, bikes and pedestrians. Public transport consists of the metro, linking all the urban cells of symbiotic city, and a light rail (tram) network, placing public transport within a five-minute walk of all symbiotic city citizens. All streets in symbiotic city have dedicated tree-lined pedestrian and bike paths. In addition, every alternate road in both the north-south and east-west road network is designed as part of a green network, with trees, water sensitive urban design principles, and pedestrian and bike priority providing a safe and comfortable sustainable transport environment. Private vehicles have access to all networks, however in 50% of these networks they have to realize that they are now in a shared environment and no longer the dominant form of transport. Parking facilities at train stations at the edge of the city will provide park + ride options to encourage reduced city destination car use.
Diverse and Sustainable Landscape
There are diverse and sustainable landscapes in symbiotic city. The purely rural cells are linked by an ecological network that incorporates sustainable living technology to provide onsite renewable energy, rain water harvesting, retention and cleaning of storm water, solid waste treatment, and organic waste treatment. The active landscape provides for the recreational and physical well being of the population. Linked to the hard and soft public open spaces are the sports, athletic and adventure grounds, sports stadia, and gymnasia. The productive landscape provides for all of the sustainable farming initiatives of symbiotic city, with hydroponic agriculture providing more than 25% of the cities vegetable requirements.