III. Urban stress


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III. Urban stress

  1. 1. URBAN MICROCLIMATES: TEMPERATURESTemperatures in Atlanta, GA (vegetation vs built areas) Urban “heat islands” : average difference between CBD and countryside = +0.6oC (morning) and +3o/4oC (evening) Watch www.youtube.com/watch?v=t-sXHl3l-rM © 2011 Antoine Delaitre 1
  2. 2. Low albedo of many urban building materials + lack of evapotranspiration higher evening temperatures © 2011 Antoine Delaitre 2
  3. 3. UBL (Urban Boundary Layer) = warm/polluted layer of air above cityUCL (Urban Canopy Layer) = warm layer of air near ground © 2011 Antoine Delaitre 3
  4. 4. URBAN MICROCLIMATES: WIND + CONDENSATIONTall constructions disrupt air flow and reduce wind speed/evaporation (except “canyon effect”) Urban “canyon effect” © 2011 Antoine Delaitre Urban pollution particles + heat convection + condensation + rain 4
  5. 5. URBAN MICROCLIMATESCHARACTERISTICS OF URBAN CAUSES AND EFFECTS MICROCLIMATE Watch www.youtube.com/watch?v=t-sXHl3l-rM •Tall buildings less wind •Pollution of fossil fuels (cars+factories) + central heating + humans heat + particles smog which traps outgoing radiant energy (greenhouse effect) “HEAT ISLAND” OVER CBD •Low albedo of most building materials (asphalt, concrete, metal) reflects (HIGHER TEMPERATURE) less solar radiation (=absorb heat during day and release it at night) •Average temperature difference between CBD and countryside = +0.6oC (morning) and +3o/+4oC (evening) less frost/snow, early blooming, more A/C. more dust particles and fumes + higher buildings less sunlight radiation (in LESS SUNLIGHT spite of higher temperatures) with considerable local contrasts however (CBD = very shaded) •Tall buildings act as windbreaks wind velocity 30% lower than in LESS WIND countryside(EXCEPT “CANYON EFFECT”) •Sometimes, high-rises can also form “canyons” which channel air and create strong local winds and turbulences (NY, Hong Kong) DRYER AIR Higher temperature + lack of vegetation = air 6% dryer than in countryside Higher temperature + wind convection + more particles to condensateMORE CLOUDS/FOG/RAIN moisture thicker and more frequent clouds/fogs over cities (5-15% more (“URBAN PLUME”) rain, 25% more thunder, 400% more hail) © 2011 Antoine Delaitre 5
  6. 6. URBAN STRESS #1: POOR HOUSINGSlum in Manila (Philippines) Port-au-Prince (Haiti) Apartment complexes in Hong Kong (China) © 2011 Antoine Delaitre 6
  7. 7. URBAN STRESS #2: CONGESTION Rush hour in Los Angeles “Go-Slow” in Lagos (Nigeria)Rapid transit (“RER”) in greater Paris area Streets in the center of London (UK) © 2011 Antoine Delaitre 7
  8. 8. URBAN STRESS #3: ENVIRONMENTAL PROBLEMS (“Brown Agenda”)An “outhouse” in Bangladesh São Paulo (Brazil) Beijing (China) Riverbanks of the Nile (Sudan) © 2011 Antoine Delaitre 8
  9. 9. URBAN STRESS #4: SOCIAL PROBLEMS Caracas (Venezuela)Family in India Belfast, Northern Ireland (UK) © 2011 Antoine Delaitre 9
  10. 10. Types of ENVIRONMENTAL AND URBAN STRESS urban stress Poor housing can be a major problem (LEDC): •Quality: water, sanitation, electricity, square footage per person, reliable construction (antiseismic, etc) Poor housing •Quantity: supply/demand (e.g. Hong Kong) •Affordability: slums vs affluent neighborhoods (e.g. Lima) •Security of tenure: ownership vs rental vs squatting (Mexico City) MEDCs: LEDCs: •Reliance on private cars rather than public •Lack of urban planning, street organization and strict transportation + competition for street space between traffic regulations congestion (e.g. “go-slows” in traffic, parking, bike lanes, pedestrian zones, Lagos) roadwork congestion (Los Angeles, London) •No traffic flow control (Lima, Bangkok) Congestion •Lack of efficient traffic flow control (Los Angeles) •Many vehicles in poor condition air + noise •Abundance of cars air + noise pollution pollution •Urban sprawl + public transportation to/from CBD •Urban growth > growth of transportation network but not adapted to inter-suburb transit between very long commute suburban edge cities long commute (SF Bay, Paris) •Lack of public funding unregulated + dysfunctional •Medieval streets not adapted to traffic (London) transportation network (e.g. Ouagadougou, Lagos) “Brown Agenda” = range of environmental problems in LEDC: Environmental •Problems linked to lack of land (Rio), water (Mexico City), green spaces (Sao Paulo) and public services (lack of problems trash collection in Cairo or Dhaka) •Problems linked to pollution: water, air (China), soil, toxic waste (e.g. 1984 industrial pollution in Bhopal, India:“Brown Agenda” 4,000+ deaths) Some common social problems in Third World cities include: •Difficult access to services for underclass (e.g. education, health, banking)Inequalities and •Ethnic/religious discrimination socio-eco polarization (Belfast, Jerusalem, Johannesburg)social problems •Poverty + limited police presence Crime (e.g. Caracas) © 2011 Antoine Delaitre 10