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Urban Ecosystems
How does a city get started?• Usually an historic trade route or location near
some valuable resource, e.g. water• Usually without any long-term planning• Usually in an area where it
is easiest to build structures,
e.g. flat or gentle terrain
(interesting exceptions
– San Francisco!)
How is a city structured?
How is a city structured?
• Most are structured through historical “accidents”
• Most do not have large, open “green spaces”
• Zoning has segregated living areas from business areas to some extent
What problems have developed because of these structures?
Problems with water• Runoff is usually polluted. With what?
• Urban runoff – fast, furious with little percolation. Why?
• Urban flooding results from this.
Some possible solutions from the Los Angles Demonstration
House
Cisterns for collecting rainwater
Vegetated Swales for moving water and retaining it within
specified areas
In this case, they used mulch rather than vegetation
Retention Structures
Driveway Collection ‘Well’
What problems have developed because of these structures?
Problems with air• Air quality is bad in cities due to
– Automotive sources– Industrial sources– Smoke from other sources
• Air quality is also bad due to lack of absorbing surfaces
What problems have developed because of these structures?
Urban Heat Island Effects
Suburban day Suburban day Suburban night
Urban day Urban day Urban night
Atlanta, GA
1973 1976 1983
1987 1992 1997
Atlanta, GA
1971
1997
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