Presentation on theme: "Urban population density"— Presentation transcript:
1Urban population density C.2. Urban LandscapeUrban population density
2Why study urban population density? Residential land use being the most important land use in a citySpatial distribution of populationTemporal changes of population distributionUrban population density curves
4Gradients of population density with cities (Gradient analysis)Two notable features(1) Absence of residential population in city center(Central crater)(2) Decline of population density from inner parts of the city to its periphery.
5Distribution of population density within a city Residential population density：decline with increasing distance from the city centrenegative exponential decline of density with distanceTemporal changes of population density
6LDC citiesRio de Janeiro, Bangkok, Dhaka, Mexico City
8Population density curves Central densityPeak densityDensity gradientPeripheral densityAreal extent
9Large-scale rural-urban migration The population density of the whole urban area continues to rise through time with the highest population density always at the city centre.The density gradient has remained relatively constant from the centreThere is a horizontal expansion of the cityBut the extent is much smaller than that of the MDCs because of late start of urbanisation and suburbanisation affected by poor infrastructure.
10SuburbanisationIn early stages, population density in the city centre increasesBut as time passes, the density gradually exhibits a declining trendPeople move out and leave a density crater at the city centreOutward movement extends the city fringeAs the population growth in the MDCs is small, the continued horizontal expansion of urban area leads to flattening out of population density very gentle density gradient
11Reasons for the spatial and temporal changes of population density within a city TRANSPORTThe most desirable, hence most expensive, site for all urban land uses lie close to the city center, where maximum accessibility is provided by converging transport routesECONOMIC FACTORThe further a site is from the city center, the greater are the transport costs involved in its use.but because of reduced competition, land rent of such sites is lowerThese lower land values encourage lower intensity of use away from the city center lower intensity of land use for residential and other uses.
12Reasons for the spatial and temporal changes of population density within a city SOCIO-ECONOMIC FACTORLow – income groups tend to live closer to center for more immediate accessibility to their working places and lower transport costs.As a result, the poor live in small amounts of the valuable / expensive lands and live at high densitiesHigh – income groups can afford the time, cost and inflexibility of longer daily journeys between the periphery and city centre Land is cheaper on the outskirts of a city, thus the rich consume more of it for their larger and more wide of spaced house.
13Reasons for the spatial and temporal changes of population density within a city HISTORICAL FACTORDue to historical process of urban development there would be a tendency for lower densities in the newly-developed areas than in the older earlier developed residential areas.
14Reasons for the spatial and temporal changes of population density within a city Increase of suburban manufacturing and retailing / commerce around the fringes of large cities now attracted residential settlement, producing multi- centred urban settlements produces lower density gradient by increasing the attraction of the suburbs and lowering the attraction of the city centerAccess to open space in suburban areasincreasing attraction of suburbscomplicating the pattern of land values in suburbs
15Variations in the rates at which population densities decrease Due todifferent per capita car ownershipthe proportion of manufacturing jobs availablethe extent of “twilight” zonesthe cost of public transportthe age and extent of the urban area
16Temporal changes of population density in WESTERN and NON-WESTERN Cities
18At time t, in the early stage of growth Residential densities are very high towards the center but decrease rapidly with increasing distance from the city centerThis reflects the early central location of factories are the absence of effective means of public transport
19At T1, centrifugal movement of residential population is made possible by increasing flexible transport system with the city peripheryThe area of maximum density moves outwards from the city center as the commercial core expands and redevelopment of old central housing occurs
20Densities decline sharply in city centre (where commercial and industrial functions displace former residents), but increase and reach further out into the suburbs with the growth of commutingThis reflects the impact of urban planning, which aims to achieve lower residential densities
21The density gradient therefore becomes more gentle Suburbanization helps to flatten the shape of the density curve by increasing the area of city.
22Temporal changes of population density in Western cities
24There is a continual increase of densities throughout the whole urban area, that is densities increase while the gradient remains the sameDue to the rapid centripetal movement of residential population from rural areas to urban areas, i.e. rural- urban migration.
25Becausethere is crowded downtown area with dense population and congestion, as people who move up socio-enonomic ladder and reside hereThey push up the slope of the density curve near and around the city centreat the same time, the periphery becomes crowded with migrants from the surrounding countrysideThe poor transport systems push outwards more slowly than western cities of similar populations.They therefore tend to be more compact and have greater overall population densities
26Temporal change of population density in non-western cities
27Changing population density around the city centre over time
28Describe the peak density. - FlattenPeak is lower and shifts away from centre
29Explain Positive reasons: Suburbanization Higher mobility Higher incomeDesire for better living environment
30Negative reasons:RedevelopmentSlum clearanceDensity controlJob opportunity, housing provision in suburban area
31What are the environmental implications of the changes in population density? 1. Improvement of inner environmentMore open spaceRemoval slum areas2. Traffic congestion, pollution3. Urban encroachment into rural
32Draw a population density curve from Central to Shatin. Include the following places: Central / TST, Mongkok/Yau Ma Tei, Kowloon Tong, New Kowloon, Shatin/Tai Po