Urbanization and the Geoenvironment - Sustainable Practices in Geoenvironmental Engineering - page 219

7
Urbanizat ion and the Geoenvironment
7.1 Introduction
In 2010, 50% of the world's population lived in cities, as compared with 20%, 10 years
before (WHO, 2014). More than 60% of the population will live in urban areas by the
year 2030, making this an increasingly signiicant component in the global environ-
ment. Cities account for 70% of the world's energy consumption and greenhouse gas
emissions. Urban centers, together with their suburbs, constitute what is now called the
built environment . This built environment includes (a) the various physical structures
that serve the community; (b) the resultant products and discharges associated with the
various industrial, municipal, and domestic activities such as wastepiles, dumps, aera-
tion ponds, gravel pits; (c) the infrastructure, such as pipelines, transmission towers,
roads, runways, bridges; (d) the various utilities necessary to service the community,
such as power plants, gas plants, wastewater treatment plants, reservoirs; (e) the other
kinds of resources associated with, and necessary to sustain the urban population and
the welfare of the community (e.g., parks, lakes, forests, recreational and sporting facili-
ties). By its very nature, the man-made environment that deines the built environment
is often in conlict with the natural environment and in particular with the goals of sus-
tainability of the land environment and its natural resources. The general perception is
that urban centers consume signiicant resources and pollute the air, land, and water.
Populations within the cities require clean air, clean water, sewage and waste manage-
ment systems, adequate food supply, housing, and transportation. It is estimated that
more than 200 million people live in cities that do not have access to clean drinking
water and that more than 400 million people live in cities that do not have access to
solid waste collection services and facilities. It is often argued that these demands are
currently not well met, and that the demand deicit will continue to escalate with time.
For example, in Accra, Ghana, only 5% of the inhabitants have access to a sanitation
network, whereas 50% do not have a septic tank or access to public lavatories (Fauchon,
2012). In Lima, Peru, 90% of the sewage (more than 16 m 3 /s), is discharged directly
into the sea. Some typical types of urban problems are summarized in the illustration
shown in Figure 7.1.
A recent deinition of urban sustainability offered at the Sustainable City Conference
in Rio (2000) stated: “The concept of sustainability as applied to a city is the ability of the
urban area and its region to function at levels of quality of life desired by the community,
without restricting the option available to the present and future generations and without
causing adverse impacts inside and outside the urban boundary.”
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