Contemporary Urban Environments

Urbanisation

The increase in the percentage of a country's population living in the city

Why are cities growing?

Rural to urban migration, industrialisation, natural increase, primacy, physical factors (relief, climate, near a river)

HIC Trends in Rates of Urbanisation

Approximately 80% of population lives in the city. Have been growing since 19th Century Industrial Revolution. Recently rates of urbanisation in HICs have significantly slowed down - counterurbanisation

NEEs Trends in Rates of Urbanisation

Fastest rates of urbanisation due to primacy, migration, industrialisation etc. Most people still live in rural areas.

LICs Trends in Rates of Urbanisation

Lowest rates of urbanisation due to poverty, debt, lack of infrastructure and resources, disease, political instability etc.

Push Factors from Rural Areas

War, political instability, genocide, crop failure, lack of clean water, poor infrastructure, natural hazards, poor services, overgrazing

Pull Factors to Urban Areas

Bright light syndrome, perception, employment, wages, SoL, QoL, transport, available food & water, better housing, political stability

Urban Theory Models

Burgess, Hoyt, Harris & Ullman, Mann

Why are urban theory models useful?

They give a simplistic and generalised overview of of city growth. They are based on the growth of cities in HICs

Why are more modern urban theory models better?

An older model will not factor in recent urban changes e.g. 1960s comprehensive redevelopment, green belts, 1980s URCs, decentralisation, transport improvements, new universities and hospitals

Bid-rent

Shows that land value decreases as you move away from the CBD. Greenbelt stops city from expanding so suburban prices go up. Industry has moved to areas with lower land prices

Urban resurgence

Reviving urban economies which can come in many ways but there was some original decline

What factors have encouraged urban resurgence?

Government decision making; growth of knowledge economy; people have chosen to move back for jobs, safety, transport and services

Sustainable community

Places where people want to live and work, now and in the future. They meet the diverse needs of existing and future residents, are sensitive to their environment and contribute to a high quality of life

Ecotown

A town designed to facilitate a lifestyle that has as little impact on the environment

Gentrification

Process by which more affluent people more into poorer inner city neighbourhoods. It contradicts the traditional urban models

Postmodernism

In the context of cities it is a term utilised after 1970s to describe unplanned growth cities

Urban structure of postmodern cities

Chaotic multi-functional structures; highly spectacular centres; large concentrations of poverty; hi-tech corridors; post-suburban developments

Architectural styles of a postmodern city

Mix of styles; spectacular iconic buildings; use of heritage; produced for specialist markets

Culture and society of a postmodern city

Highly fragmented; lifestyle divisions; high degree of social polarisation; groups distinguished by their consumption pattern

Microclimate

The climate of a very small or restricted area, especially when this differs from the surrounding area

Urban heat island

A city or metropolitan area that is significantly warmer than its surrounding rural areas due to human activities

Factors creating UHIs

Tightly packed streets; car parks; concrete buildings; dark roofs

How can people lessen the UHI effect?

More trees should be planted and reflective roofing installed as well as growing roof top gardens. Oaks and maples are the best trees because they are big and leafy which provide shade and use the sun's energy to grow and give off water vapour

Urban form

The physical characteristics of built up areas including the shape, size, density and make-up or configuration of settlements

Urban form: population

Globalisation has brought increased migration which makes it difficult to provide services for everyone

Urban form: environment

Established physical infrastructure such as sewage systems need to keep pace with population change

Urban form: economy

Industry has tended to locate in centres of population. As suburbanisation increases, industries follow

Urban form: technology

Some industries are pulled towards wired networks or data processing hubs where there is high-speed internet and new technologies. Teleworking is challenging the notion of work hubs

Urban form: policies

Government policies affecting housing, planning and transport and the economy will restrict or encourage changes at different times in different urban locations

Characteristics of megacities: urban sprawl

The expansion of the urban area, usually with insufficient urban infrastructure such as streets, parks and utilities

Characteristics of megacities: peripheral growth

Development of new growth poles and dispersed settlements

Characteristics of megacities: edge cities

Surrounded by new forms of retail, leisure, industrial and business parks, miscellaneous warehousing and large employment buildings, ring roads and motorway interchanges

Characteristics of megacities: high-density living and intensification of urban centres

Vertical residential zoning such as super high-rise developments, small three-story family homes and one-room studio apartments

Characteristics of megacities: residential differentiation

Different socio-economic got ups are likely to live geographically apart; also likely to be a housing shortage for the poorest, forcing them into inadequate housing units

Characteristics of megacities: redevelopment and conversation

Protection of historic cores; redevelopment of former industrial sites

Characteristics of megacities: infrastructure

Ageing infrastructure likely to dominate with some areas poorly served

Characteristics of megacities: transit-oriented development

Urban areas around railway station and major road routes

Characteristics of megacities: car dominated urban form

Led to lower density housing estates on the edge of cities. Leisure, retail and employment follow, raising issue of using more fossil fuels to get there

Characteristics of megacities: environmental problems

Including increased levels of pollution, health and waste concerns

Fog in urban areas

The higher concentration of condensation nuclei in urban areas encourages fog formation especially with cooler overnight conditions. Beijing and New Delhi experience thick smog due to carbon emissions

Thunderstorms in urban areas

The rising heat in summer can trigger heavier and more frequent late afternoon/early evening thunderstorms

Wind in urban areas

Urban structures greatly interfere with wind by slowing, redirecting and disturbing the airflow; mean annual wind velocities up to 30% lower than in rural areas

Urban canyons

Relatively narrow streets bordered by high-rise buildings funnelling and so concentrating winds

Venturi effect

A particularly violent form of gusting caused in particularly narrow gaps by air rushing to replace low pressure vortices beyond structures

Why is urban air quality so poor compared to rural areas?

Carbon monoxide causes heart problems, headaches and tiredness

Twice as much carbon dioxide leads to enhanced greenhouse effect

Ten times more nitrous oxides causes haze, respiratory problems and acid rain

Two hundred times more sulphur dioxides causes haze, respiratory problems, acid rain and damage to plants

Smog

A mixture of smoke and fog. Occurs when smoke particulates and sulphur dioxide from burning coal mix with fog. Most likely to be cause by sunlight reacting chemically with industrial and vehicle emissions to form a mix of secondary gases

Legislation on air pollution

Clean Air Acts throughout HICs have been hugely influential. There has been research into the hazardous effects of diesel particulates

Why is there more precipitation in urban areas?

Warmer air can hold more moisture; dust and pollution make more condensation nuclei

Impacts on drainage basin storage areas: rivers

Urban rivers are primarily the exit for water transferred through the drainage basin, but they are also important stores. Management (dredging, embanking, channelisation) will increase storage capacity

Impacts on drainage basin storage areas: surface stores

Reservoirs, lakes, ponds and swimming pools are permanent stores but vulnerable to evaporation. Puddles following rain are temporary

Impacts on drainage basin storage areas: interception storage

Interception storage is reduced owing to the replacement of vegetation by impermeable structures such as buildings, roads and pavements engineered to drain the water rapidly to the nearest river

Impacts on drainage basin storage areas: soil

Clay soils retain more water than sandy ones, but there is less soil storage capacity as urban development reduces exposed surfaces and vegetated areas

Why is measuring, recording and understanding the relationship between discharge and precipitation essential in urban areas?

There is an increased flood risk caused by the higher proportion of urban precipitation making its way into river channels and the speed that it happens

Contemporary urban environmental issues: atmospheric pollution

Concentrated energy use and vehicle emissions lead to greater air pollution. Clean air legislation, vehicle restrictions and technical innovation are improving air quality in many cities

Contemporary urban environmental issues: water pollution

Comes from domestic waste; industry; leaching from illegal dumping and poorly managed landfill; and rainwater runoff from roads, pavements and rooves

How is water pollution being managed?

Sewage treatment and legalisation in HICs. Organisations such as UN and World Bank are investing huge resources into water quality and supply issues in NEEs and LICs

Contemporary urban environmental issues: dereliction

Results from:

Ageing and decay of building over time

Movement of urban activities to better and more profitable locations

Changes in urban economy brought about by deindustrialisation

Contemporary urban environmental issues: brownfield site development

Thousands of brownfield sites have been contaminated by previous industrial uses and decontamination is time-consuming and very expensive. Not all brownfield sites have physical access necessary for residential development. Neighbouring land might still be used for industrial purposes

Why are brownfield sites a valuable urban resource in the UK?

Their redevelopment for housing starts to address the pressing need for more homes, improves the urban environment, reduces urban sprawl (protects green belt), and reduces demand on car use (commuting from suburbs or further afield)

Ecological footprint

The area of land needed to provide the necessary resources and absorb the wastes generated by a community

Liveability

Describes the natural, physical, social and economic dimensions of sustainability in an urban context

Features of a sustainable city: greener built environments

Using energy and water more efficiently, reducing MSW and managing it better

Features of a sustainable city: improved transport

Developing infrastructure, networks and modes to meet demand without increasing congestion and pollution

Features of a sustainable city: planned expansion

Encouraging compact cities rather than urban sprawl

Features of a sustainable city: conserving buildings and open spaces

Restoring historic buildings, brownfield clearance to create new green spaces and protection of existing open spaces. Improving biodiversity within urban river systems and ecosystems is important

Features of a sustainable city: carbon-neutral development

Building structures such as houses that generate as much energy as they use to reduce pollution (e.g. BedZED)

Challenges in developing more sustainable cities: political will

There needs to be long term strategic planning involving all stakeholders

Challenges in developing more sustainable cities: globalisation

The interconnected cities of the world has increased the power and influence of TNCs which must also embrace the need for change

Challenges in developing more sustainable cities: economic gains for all

There must be economic incentives for both the wealthiest and poorest if positive change is to happen

Challenges in developing more sustainable cities: climate change

Sustainable cities must stimulate economic growth without increasing greenhouse gas emissions

Characteristics of urban microclimates

2-3 weeks fewer frosts

5-10% more cloud

Lower relative humidity

5-15% more precipitation

Higher pollution levels

Fog and photochemical smog more likely

More chance of hail and thunderstorms

Canyon effect

Surface roughness

Reduces windspeed and generates turbulence

Why is there more precipitation?

Greater density of condensation nuclei

Updraughts of unstable air

Convection caused by urban heating

Why are there higher pollution levels?

Smoke; diesel particulates; CO2, SO2, nitrous oxides and hydrocarbons

Factors contributing to UHIs: heat absorption

Extensive dark surfaces such as Tarmac and rooves absorb heat during the day and release it slowly at night

Factors contributing to UHIs: reflection

Glass and steel reflect heat into surrounding streets

Factors contributing to UHIs: reduced evapotranspiration

Far less vegetation than rural areas, so less evapotranspiration. Drains and sewers remove surface water quickly so the humidity is reduced. Less heat is lost in evaporating it

Factors contributing to UHIs: buildings

Poor insulation leaks heat in winter and air conditioning pumps hot air into the streets in summer

Factors contributing to UHIs: precipitation

Rising heat, water vapour from power stations and industry, and condensation nuclei from air pollution provide the conditions necessary for precipitation. More frequent and heavier thunderstorms

Factors contributing to UHIs: other

Power stations, industries, vehicles and the inhabitants all generate their own heat

Issues associated with cultural diversity: economic

Migrants may meet labour shortages in the tertiary and secondary sectors but often the perception of "jobs for migrants" causes racial tension and intolerance, especially during recessions

Issues associated with cultural diversity: housing

New migrates generally are poor upon arrival. Multiple occupancy in a rented property is widespread. Ethnic minorities have traditionally been less successful at securing mortgage loans. Residential succession often occurs

Residential succession

The process by which established ethnic groups move to suburban locations leaving the housing empty for newly arrived migrant groups to subsequently occupy

Issues associated with cultural diversity: education

Children will usually attend their nearest school. In some parts of urban areas, concentrations of ethnic minorities has led to schools being dominated by one ethnic group. Has an impact: for example, additional English lessons may be necessary and special religious provision may be requested by parents

Issues associated with cultural diversity: health

Many ethnic minorities continue to live in inner-city areas so there tends to be a close association with poorer levels of health. However, this is more a result of the environment

Issues associated with cultural diversity: religion

People might wish to follow their own religious calendars which can cause friction with employers and local communities. Misunderstanding of practices like traditional clothing is also a potential cause of conflict

Issues associated with cultural diversity: gender

Women from ethnic minorities might adopt different cultural preferences. This might be a tendency for women to be the primary carers of dependents. Therefore they are disadvantaged in terms of employment

Issues associated with cultural diversity: food culture, pop music and sport

These all help to support what is described as interculturalism. Around 75% of Europeans consider sport as means of integration

Issues associated with cultural diversity: language

If the host country language is not adopted quickly, it will acts as a barrier to integration and restrict employment and education opportunities