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Chapter 29

Chapter 29. Urban Environment. The City as a System. A city influences and is influenced by its environment A city must: Maintain a flow of energy Provide necessary material resources Have ways of removing waste Accomplished though transportation and communication with outlying areas

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Chapter 29

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  1. Chapter 29 Urban Environment

  2. The City as a System • A city influences and is influenced by its environment • A city must: • Maintain a flow of energy • Provide necessary material resources • Have ways of removing waste • Accomplished though transportation and communication with outlying areas • A city depends on other cities an rural areas • If the city declines, the outlying area declines • If the outlying area declines, the city declines

  3. Two futures for cities • Pleasing and livable • Resources from outside the city • Allow room for wilderness, agriculture & forestry • Environmentally negative • Decay from the inside • People move to more expansive suburbs • Poor remain in the city • Technological structure declines • Pollution increases

  4. Importance of Site and Situation • The location of a city is influenced by: • Site: the summation of all environmental features of that location • Situation: the placement of a city in respect to other areas • Ex) fall line

  5. Site • Geologic substrate suitable for building • Firm rock base • Well drained soil above water table • Nearby water supply • Nearby land for agriculture • Benign climate (no extremes)

  6. Situation Two main situation issues – transportation and defense Waterways: for transportation fall lines: an abrupt drop in elevation of the land -used for energy -farthest inland that a large ship could navigate -farthest downstream a bridge could be built

  7. situation • For defense • Peninsula • Geologic outcropping • Mineral resources • USUALLY CITIES ORIGINATED WHERE THE SITUATION PROVIDED A NATURAL MEETING POINT FOR PEOPLE

  8. The History of a City • Read “A Closer Look 29.3” and summarize • 4 Stages: • The rise of towns • The era of classic urban centers • The period of industrial metropolises • The age of mass telecommunication, computers and new forms of travel

  9. City Planning for Defense and Beauty • City Planning • Formal, conscious planning for new cities • 2 themes of city planning: defense and beauty • Washington DC was built by Pierre Charles L’Enfant for aesthetic considerations

  10. The City as an Environment • Energy budget • Urban atmosphere and climate • Solar energy • Water • Soils (made lands) • Pollution

  11. Energy budget • Exchange of energy • Absorption and reflection of solar energy • Evaporation of water • Conduction of air • Wind (convection) • Transport of fuel into city and use of fuel with in the city • Convection of water (stream flow)

  12. Urban Atmosphere • Less wind, due to buildings obstructing the flow of air • Channel wind – wind tunnels created between buildings. Careful where to place new buildings • Less sunlight due to particulates • Warmer temperature • Increased burning of fossil fuels • Lower rate of heat loss – bldgs and pavement act as solar collectors

  13. Solar Energy • Until modern time it was common to use solar energy to help heat homes (Romans) • Solar photovoltaic devices are now a common sight in cities • Illegal to block the sun from another building

  14. Water • Rain runs off into storm sewers • Prevents water in soil from evaporating into atmosphere – which normally helps to cool ecosystems – adds to urban heat island effect • Cities tend to have higher rainfall due to particulate providing a place for water to condense on. • Single underground sewer systems- handles only sewage when not raining, and sewage AND rainwater during storms

  15. Soils • Soil is covered by cement, asphalt and stone • No natural cover of vegetation that would put organic matter back into soil • Therefore, organisms die • Weight of buildings compacts the soil and restricts water flow • Some cities have “Made Lands”. Soil created from “fill” --- trash, dumped items, etc.

  16. Pollution • Concentration of everything exposes more people to higher conc. Of pollutants. • Early deaths result • Los Angeles = loss 1-2 yrs of life • Pollution comes from • Motor vehicles • Stationary power sources • Home heating • Industry • Nitrogen oxides, ozone, carbon monoxide, sulfur oxides, VOC’s

  17. Bringing Nature to the City • Cities favor certain animals and plants • Trees are important to urban environments • Cities help conserve biological diversity

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