Urban Growth Fact Sheet
This resource examines the issue of urban growth in Christchurch. It looks at the factors driving urban growth, why it is an issue and what problems it raises, and what is being done to manage it.
What factors are behind urban growth?
The expansion of the urban area has two main causes (which are usually inter-related):
- Population and household growth
- Economic expansion
Population and household growth
In recent years Christchurch’s population has increased considerably, compared to previous rates.
As can be seen the rate of increase between 1991 and 1996 is noticeably higher than for example the period 1986 to 1991. The higher rate of increase coincides and is largely a result of the high levels of migration into Christchurch experienced in the early nineties.
Urban expansion is also driven by the increase in the number of households being formed. A trend over the past twenty years is for a decrease in the average number of persons per household. In 1976 the average household occupancy rate was 3.1 people. This declined to 2.8 by 1986 and reached a low of 2.6 in 2001. With less people living in one household a greater demand is created for new housing. Reasons for this increase in household formation include:
- The rise in divorce and separation, which has split households in two;
- The trend towards marriage at older ages results in people spending greater time in ‘multiple person households’ (flats) or living alone rather than in family households;
- More elderly people with greater life expectancy living for longer periods on their own.
Economic expansion
The other main cause of urban growth is economic growth. Economic expansion promotes greater industrial and commercial activity, such as factory building, expansion of specialist uses such as the airport and railway depots, road building and widening; and promotes more house building. Generally people choose to build their homes when economic times are good and business confidence is high. The peak levels of house building this decade coincides with the peak periods of economic growth, which can be seen on the graphs at the bottom of the page. Note that a dwelling is defined as a detached residential building on its own site, while a unit is a residential apartment erected in conjunction with several other units on the same site.
Christchurch migration
The patterns of land use above the aquifers can influence their quality, for example the risk of contamination from industrial sources can be reduced by limiting zoning for industrial uses to those areas of land where the underground aquifer is capped by a protecting layer of clay.
Protection of high quality soils
Most remaining areas of high quality soils in Christchurch occur immediately beyond the existing urban boundary – the northwest from Belfast to Harewood, Avonhead, Templeton, Marshlands and Halswell-Wigram.
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The urban growth issue
Why is urban growth an issue?
To answer this question we can look at some of the concerns generated by urban growth:
Potential conflict between the scale and the desired character of the City
There are certain features of Christchurch that make it unique and which underpin its identity. The key element in Christchurch’s identity is the contrast and transition from urban to rural environments, particularly the contrast between the rural Port Hills and urban city, and the variation of densities within the city. City growth on the city’s edge needs to be managed to reflect the desired image and form so that this contrast is maintained, for example by limiting new development on the Port Hills.
Change within existing areas
Urban growth can promote significant change within the existing urban area through redevelopment and infill of existing properties to higher levels of development. This can result in greater coverage of land by buildings, bigger and bulkier buildings compared to existing neighbours, loss of large trees and greater traffic on the streets.
The intensity and dispersion patterns of air pollution
Christchurch’s air pollution comes from two main sources, domestic fires and motor vehicles. The dispersal patterns of pollution from these sources, especially motor vehicles can be influenced by land use patterns and the form of the city.
Where activities are more spread out a higher rate of car usage generally results in greater levels of car pollution.
Protection of the aquifer
Christchurch draws all of its water from underground reserves, or aquifers. In parts of the city, especially the west around Halswell, Islington and Harewood the groundwater is not protected by an overlying surface clay layer and there is risk of contamination from a number of sources:
- leaks and spillages from underground storage tanks, sewers, and septic tanks;
- contaminated storm water;
- old landfills;
- toxic waste from industry and agriculture.
Protection of ecological systems
Small areas of remnant wetland occur around the Avon - Heathcote estuary, Travis Swamp, Bottle Lake and Brooklands. Urban development close to these areas can interfere with their ecological systems, through for example contamination of water and soil, and reduction in buffer zones, and a greater presence of predatory animals such as cats and dogs, which prey on native wildlife.
Risk from hazards
The Christchurch area contains large areas that are vulnerable to actual or potential hazards, such as flooding, especially round the airport and adjacent to the Heathcote and Avon rivers, Halswell and Brooklands; subsidence due to deep layers of peat such as is present around Cranford Street, and instability due to erosion such as is sometimes encountered on Moncks Spur and Scarborough. Sea level rise as a result of the enhanced Greenhouse effect is also an important consideration for areas around Brooklands.
Uncontrolled urban growth may expose people unnecessarily to danger from these hazards.
Potential conflict with existing uses
The growth of the City can potentially conflict with several existing uses located in the rural zones surrounding the urban area. For example residential housing close to the airport may generate complaints over noise, which ultimately may lead to restrictions being placed on the airport operations. Similar activities are the Ruapuna Raceway and the various quarries to the city’s west. To protect the viability of these existing uses, and the general well being of the city’s residents, conflict between the two should be avoided through ensuring incompatible activities are well separated from each other. Some of the concerns highlighted above are summarised a Erosion.
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The management of urban growth
The challenge facing planners is to accommodate population and household formation growth, and economic expansion, while taking into account those concerns listed above. The Council has chosen to tackle this challenge through placing primary emphasis on consolidating the urban form. That is, encouraging most new growth to locate within present urban boundaries, rather than allowing the city to spread continually further outwards. The Council believes consolidation is the best option because it is the most energy efficient and has the least adverse effects on natural resource values such as water and air quality, high quality soils, ecologically sensitive areas such as Brooklands Lagoon and high quality landscapes such as the Port Hills, by limiting the amount of outward expansion.
Consolidating the urban area reduces the likelihood that people will be exposed to natural hazards, such as tsunami and flooding from the Waimakariri River.
Compared with other options urban consolidation is also the most cost effective means of servicing (i.e. Water and sewer connections) future urban growth. Consolidation assists in achieving a reduction in private car-borne trips, decreasing car pollution and the use of fossil fuels. Trip lengths can be shortened by locating housing close to employment, schools and business areas. Increased population densities also promote greater use of public transport.
To accommodate this growth within the city boundaries, the Council has rezoned areas around the city centre and suburban focal points to allow for a higher density of development. This means that six houses may be able to be erected on a site of 1000m2 in the L4 zone, a relatively high density zone, whereas only two could be erected on a similar sized site in the L1 zone, a low density zone.
There is evidence that the strategy is working, in that the density of development in inner city areas is increasing.
Consolidating the urban form raises issues in itself. In many inner city areas a marked change in character is sometimes experienced. For example an area characterised by old villas may come to be dominated by new three storey apartments. Many more people are living closer together so more noise and traffic is generated and there is less greenery and open space. Some people are also concerned with the design of new development, as they consider it out of scale and unsympathetic to the local environment. The Council recognises the problems that excessive intensification of the inner city brings, and as a ‘safety valve’ allows for some further urban growth on the periphery and has rezoned large areas of land at Halswell and Styx, among other places.
The Council is also working with other councils to look at urban growth not only within Christchurch but also within the Canterbury region. Among the options being explored are the creation of a ‘second city’ at Rolleston, the creation of a northern corridor centering on the Rangiora and Kaiapoi townships and development of the Lyttleton Harbour basin. Christchurch Change in Densities 1986-1996
Other sources of information
Relevant information such as committee reports and newspaper articles can be sourced from the Aotearoa New Zealand Centre at the Central City Library (add link Gloucester Street – 941 7923 and the Christchurch Environment Centre), 64 Kilmore Street – 379 2257. Librarians at the Central City Library are available to assist with research projects, as are staff at the Christchurch Environment Centre.
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