Geoscience Reference
In-Depth Information
6
Urban environments
Kevin Taylor
6.1
reservoirs for contaminant storage. As a result,
our knowledge base on urban sedimentology, and
the interactions with hydrology, air quality and
biodiversity, is rapidly increasing. This chapter
describes urban sedimentary environments, the
sources of sediments to these environments,
the physical and chemical characteristics of the
resulting accumulated sediment, and discusses
the impacts of intrinsic and extrinsic processes
upon these sediments. Finally, the sustainable
management options for urban sediments and
their impacts will be discussed.
INTRODUCTION AND DEFINITIONS
6.1.1 Introduction
The urban environment is one that is of increas-
ing importance globally, with implications for
both hydrological and sedimentological systems.
It has been estimated that 50% of the Earth's
population live or work in an urban environ-
ment (United Nations 2003) and this percent-
age is predicted to increase. Urbanization dates
back several thousand years, with development
taking place primarily along major rivers acting
as waterways. It was not until the Industrial
Revolution in Europe, and later throughout other
parts of the world, however, that the growth
of significant urban areas took place. The very
nature of urban land surfaces and waterways
results in unique hydrological, sedimentological
and atmospheric environments, leading to a wide
range of specific management and sustainability
issues, many of which are not encountered in
natural environments. The application of process
models derived from observation and measure-
ment of natural systems to urban environments
is, therefore, of limited value. The issues of
environmental pollution and sustainability have
resulted in a plethora of research into the quality
of urban air, groundwater and, to a lesser extent,
surface water. Urban sediments, and the role
of the urban environment as a sedimentary sys-
tem, have been largely neglected. It is increasingly
being recognized, however, that particulates in
urban environments are a major factor in human
health, through their impact upon air quality,
waterways and biodiversity, through the role of
sediments as vectors for contaminant transfer and
6.1.2 Definitions
The term
urban
is used widely throughout both
social and scientific literature, and has come
to mean different things to different people.
A definition suggested here for urban areas is
'those areas where the ecosystem is significantly
modified by human settlement and associated
activities; they are characterized by a unique
modification of the physical, chemical and bio-
logical environments, resulting from the con-
struction of buildings on a large scale'. One
key element of the urban environment that dis-
tinguishes it from the environments discussed
in the other chapters of this topic is its highly
engineered nature. Such engineering results in
land surfaces with distinct physical and chem-
ical properties. Although natural environments
have inevitably been altered by anthropogenic
activity, these have not resulted in the signific-
ant, and wholesale, change in fundamental pro-
cesses of sediment and water movement and
accumulation seen in urban environments. These
include increased storm peaks and shortened
