Introduction to the Research Problem
You are to consider how much of a city's built environment is claimed by machine space (space which is set aside exclusively for the care and use of machines). Much of an urban area's built environment is, for example, devoted almost exclusively to use by automobiles, buses, and trucks. Streets, parking lots, driveways, and loading ramps occupy well over half of all surface area in some parts of the city. But other machines and equipment occupy -- and dominate -- other space as well. Cooling towers for ventilation systems take up a notable amount of space, as does equipment needed to maintain telephone, electrical, water, and wastewater systems. Most people fail to perceive how much of the urban environment is given over to machines. Yet, machine space has tremendous effects. The concrete and asphalt used to pave streets and parking lots can change the microenvironment of the city. Average urban temperatures rise (the heat island effect) and concentrations of dust and particulates in the air increase. These changes are sometimes powerful enought to change patterns of precipitation over some cities. Machine space also adds to the impervious cover that alters the flow of rainwater through the urban ecological system. Finally, machine space can be a source of pollution as runoff and wind sweep hydrocarbons, chemicals, and other pollutants into the water and air.
|Your task is to explore how much of the urban built environment is occupied by machine space and whether the amount of machine space is correlated with landuse and distance from the center of the city. The map to the right illustrates how you will present the data you gather. It presents a small section of Austin, Texas, zoned for single-family housing. The shaded areas designate machine space in that neighborhood.||
||The concept of Machine Space was introduced by Ronald Horvath in a 1974 Geographical Review article. According to Horvath, ". . . technology has been viewed largely as an aspatial phenomenon, and one of the major tasks here will be to translate technology into explicitly spatial terms. If geographers are to participate more fully in planning and monitoring future technological growth, explicit recognition of the spatial dimensions of technological change will be necessary. Machine space, or territory devoted primarily to the use of machines, shall be so designated when machines have priority over people in the use of territory. Automobile territory in modern American cities exemplifies the concept of machine space." (Horvath 1974, 167-168).|
|Between 1950 and 1970 one of the key spatial expressions of technological
change was the rapid expansion of the Interstate Highway system and other
improved roads. During this time the number of automobiles in the United
States grew very rapidly. It is estimated that in 1950 there was 1 car
for every 6 Americans. By 1970 that ratio had grown to nearly 1 car for
every 2 people. At the same time, the number of highway deaths also grew
significantly. Horvath's article appeared at a time when pedestrian spaces
were being expropriated by cars. Machine Space was increasing at
the expense of people space.
The degree to which the urban environment is given over the machines varies according to the predominant land-use. Residential areas tend to have less machine space -- industrial areas, more. But, all machine space is impermiable cover. The amount of machine space in a city has implications for air and water quality, as well as the quality of life in the city.
Effects of Urbanization on Environment: An Overview by Kenneth E. Foote and Katrin E. Molch
The interaction between society and environment is a fundamental theme of much geographical research. Cities are an excellent place to study these interactions. The process of urbanization results in large numbers of people gathering in relatively small areas. There the effects of habitation are concentrated and focused. Human effects on the atmosphere, lithosphere, hydrosphere, and biosphere are often so pronounced that cities can be said to create their own environments. They do this in a number of ways:
Cities create their own environments and, as they do so, they exert powerful effects on the atmosphere and climate. Among the most important of these are:
Cities are made of concrete, asphalt, brick, stone, and steel. These materials absorb and reflect energy differently than vegetation and soil. They absorb more radiant energy and radiate this energy back into the atmosphere at different times through the day. The result is that cities are warmer than the surrounding countryside, sometimes considerably. Furthermore, cities remain warm well into the night when the countryside has already cooled.
This heat influences air circulation and patterns of precipitation.
Human activities release a wide range of emissions into the environment including carbon dioxide, carbon monoxide, ozone, sulfur oxides, nitrogen oxides, lead, and many other pollutants. Some of these emissions are toxic and have claimed many lives in some cities when concentrations reached dangerous levels as in the "killer smogs" of London in the 1950s and 1960s. Others emissions such as carbon dioxide, act to trap heat in cities. Cities also release quantities of dust into the atmosphere, with effects like those mentioned next.
The dust and emissions released into the atmosphere alter patterns of precipitation over the cities and in areas downwind. Cities often receive more rain than the surrounding countryside since dust can provoke the condensation of water vapor into rain droplets. Dust carried downwind from cities and industry can increase rain in city shadows. One of the most notable of these rain shadows, the La Porte anomaly in Indiana, is diagrammed below.
Urbanization has similar effects on land resources. Natural land cover is disturbed as cities are built leading to:
Rapid development can result in very high levels of erosion and sedimentation in river channels.
Pollutants are often dispersed across cities or concentrated in industrial areas or waste sites. Lead- based paint used on roads and highways and on buildings is one such example of a widely dispersed pollutant that found its way into soil. But humans also bury tremendous amounts of waste in the ground at municipal and industrial dumps. These materials can severely contaminate soils. Even such commonplace items like gasoline storage tanks at filling stations have the potential to cause serious contamination. When this problem was discovered a decade ago, hundreds of storage tanks had to be removed and replaced with safer containers. The most extreme cases of industrial pollution, as at Love Canal in Buffalo, New York, have forced the abandonment of large tracts of land.
The first picture shows the University of Texas at Austin as seen from the Capitol before 1895. On the second picture a part of the University of Texas campus and downtown Austin as it is today can be seen.
Urbanization has a great effect on hydrology, for a number of reasons.
As cities grow, natural groundcover changes dramatically. Natural vegetation and undisturbed soil are replaced with concrete, asphalt, brick, and other impermeable surfaces. This means that, when it rains, water is less likely to be absorbed into the ground and, instead, flows directly into river channels. Not only does more water reach the stream channels, but it arrives far more quickly after a storm. Natural vegetation slows run-off, concrete and asphalt speed the flow. The result diagrammed below indicates how urbanization speeds run-off and produces higher peaks of flow.
Higher, faster peak flows change streams channels that have evolved over centuries under natural conditions. The result is a spread of the channel vertically and horizontally to carry the extra flow. Rapid erosion of stream banks and down-cutting of stream beds occurs. When the existing stream beds cannot handle the increased flow, they flood the surrounding urban area, particularly development within adjacent floodplains.
Flooding can be a major problem as cities grow and stream channels attempt to keep up with these changes.
Click here to see examples of flood damage in Austin.
Often humans intervene to speed the flow of water through stream channels and to control erosion. Many different methods exist to control flooding and the flow of streams. Banks may be reinforced with plants, rock, or concrete retaining walls. In extreme cases, a stream may be "channelized," that is totally lined with concrete. Such channelization turns the stream into a very efficient culvert. Unfortunately, such channelization has the disadvantage of simply shifting the burden of the extra water flow downstream to other communities.
Click here to see examples of flood control measures in Austin.
As they grow, cities also tend to encroach on flood plains. These are low-lying areas that can hold and absorb overspill from stream during periods of high water. This encroachment of courses places humans in the way of floods. But encroachment also effects a watershed's ability to manage waterflow naturally. Excess flow may be kept out of floodplains by forcing extra flow downstream at higher speeds, with obvious consequences. Erosion and down-cutting will increase and the danger to downstream communities will increase.
These changes in the flow of precipitation into and through urban watersheds holds a number of consequences of water quality.
An increased area of exposed and soils and higher runoff speeds means that more sediments are carried into local and downstream watersheds. This leads to increased rates of sedimentation.
As water washes across urban surfaces, it dissolves and carries pollutants into streams and rivers. Toxic chemicals, oil, and other pollutants are all deposited in the watershed, sometimes in sediments. Also, most cities use rivers to dispose of the affluent from sewage treatment. Nowadays, it is relatively rare in the United States for untreated sewage to be discharged into waterways since storm and sanitary sewers have been divided for the most part into separate systems, but it does happen from time to time.
Click here to see examples of pollution of Austin rivers.
One of the most interesting aspects of these processes is that they interact to reinforce one another. Atmosphere disturbances caused by urban activities increase precipitation, which increases erosion, which carries more sediment into river channels. Disturbances of land can cause disturbances of aquatic environments and increased levels of dust in the atmosphere. These cyclic and cumulative effects mean that urban ecological relations can become particularly complex. One change leads to another and another in a complicated, spiraling series of feedback loops.
||Sometimes it is easy to see how urbanization shapes the environment, particularly in peripheral areas were large suburban developments may consume hundreds of acres per year. But the impacts of urbanization begin early. Sometimes, the period of initial urban settlement produces the most radical changes in watersheds as tracts of land are cleared for the first time. Encroachment continues long beyond initial settlement as an almost continuous process. These maps of "machine space" show how the area of impermeable surfaces increases through time.|
Click here to see examples of encroachment of Austin rivers and streams.
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Created 10/30/96 by Shannon Crum. Last updated 10/30/96 by slc.