Growing cities become less dense

Written January 30th, 2015 by

Cities become less denseThere is a misbelief among those in the press and some urban analysts that as cities become larger they become more densely populated. The article World Megacities: Densities fall as they become larger published by newgeography indicates the opposite is true.

newgeography builds on the groundbreaking work (such as in Planet of Cities) performed by New York University geographer, Professor Shlomo Angel. newgeography concluded population densities were falling in each of the 34 mega cities analysed.  One example was London. Even though urban sprawl is heavily constrained by greenbelts created following World War II, “London’s density is estimated to have dropped by two-thirds”.

This trend extends even to the lowest income cities, such as Addis Abeba (Ethiopia), where the population has increased more than 250 percent since the middle 1970s, while the urban population density has declined more than 70 percent. The rapidly growing cities of China exhibit the same tendency.  According to newgeography, with the newly classified megacity of Tianjin, “approximately 85 percent of Tianjin’s recent growth has been outside the core districts”.

A factor in Australia that will cause lower densities is the changing makeup of households in the future. The Household and Family Projections, Australia, 2011 to 2036 release by the Australian Bureau of Statistics, show the number of people living alone is projected to increase.  In 2011 this household population was 2.1 million and is projected to increase by between 61% and 65% over the projection period to between 3.3 and 3.4 million in 2036.  Just over half of people living alone are females and this reflects the higher life expectancy of women.

Forecaz Modeller provides for changing occupancy rates over future projection years, both for attached dwellings (units/townhouses) and detached dwellings (houses).  This feature allows the population densities in the urban growth models to decrease over time, whilst the overall population continues to increase.

Even though the urban planning strategy in many areas has been “up not out”, urban planners must accommodate development growth occurring near to or at the urban fringe.  As cities expand, they should ensure they secure the necessary land for roads, infrastructure networks, and public open spaces in advance of development.

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About the Author:
Bradley is the founder and Managing Director of Sizztech. He is an enterprise ICT consultant with over twenty years of experience in the Information Technology industry. In the last eight years Bradley has specialised in delivering web based geo-spatial solutions that focus on supporting capital works planning and delivery. This has lead to Sizztech developing Forecaz Modeller, an automated tool that performs urban growth modelling and forecasting.

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