Geography Reference
In-Depth Information
The geographical injustice of urban water
access and management is a fruitful field for
applied geography.
cannot afford coastal protection works. Subsidence
affects many parts of urban areas.
In 1997, a garden in Ripon in Yorkshire, UK,
disappeared into a 40 m deep hole. Within hours,
a double garage disappeared, along with the
children's sandpit. The house involved and two
neighbouring dwellings had to be evacuated. They
were built above soluble Triassic gypsum, which
extends along the eastern edge of the Pennines
and also occurs in Cheshire. Such karstic solubility
phenomena have to be considered when planning
new housing estates.
Over much of southern Britain, and in many
other countries, the problem of cracking clay soils
provides a major constraint on urban
development. Many clay soils expand when wet
and shrink and crack during long dry periods.
Such 'shrink-swell' phenomena cause differential
shifts of parts of the structure, such that floors tilt
slightly and windows and doors no longer close
properly. Such natural subsidence may be covered
by household insurance, premiums for which were
previously based on the pattern of past claims.
Now geographers are assisting companies in
mapping the hazard due to cracking clays
(Doornkamp 1995).
Any form of land development alters the form
of the slopes and the passage of water over the
ground and into the weathering profile. Landslide
and soil erosion potentials are altered.
Developments in steep granitic terrain in Hong
Kong, the Rio de Janeiro area of Brazil and
peninsular Malaysia have led to large-scale
landslides, severe gullying and soil erosion. Impacts
can be divided into two phases of the
development process: those during project
construction and those in the period after
completion of building work. Geographers have
helped to develop guidelines for the recognition
of landslide potential and for erosion control.
Six key contributions can be made by
geomorphologists to urban environmental
management (Hart 1986):
Competition for groundwater resources, depletion of
aquifers and subsidence
Delhi illustrates how most low-latitude cities have
outgrown the municipal water distribution
systems. Many rich people sink wells, saving water
charges, but lowering the water table and forcing
people to dig deeper. This again tends to deprive
the poor of access to cheap, good-quality water
and may also induce the type of subsidence that
has affected Bangkok and Mexico City.
Competition between rural and urban areas for water
supplies
Another controversy arises in trying to balance
urban and rural water needs. With a
per capita
consumption of around 220 litres per day, Delhi
uses twice as much water per head as Bombay.
Rural people protest that water is used for
swimming pools in Delhi, while they do not have
enough for their crops. Within the city, water is
used to keep politicians' lawns green, while the
middle class do not get enough pressure for a real
shower and the slums are not connected to the
water mains at all.
THE ROLE AND SIGNIFICANCE OF
URBAN GEOMORPHOLOGY
Every climatic, topographical and geological
situation creates problems for the construction and
maintenance of cities. Some of these are due to
processes occurring at present, and some are
legacies from the past, such as the remobilisation
of ancient landslides, or foundation problems due
to complex subsurface conditions in sediment laid
down in past climates, greatly different from those
of the present. Many cities face earthquake,
volcanic, tsunami or avalanche risks. Possible
worldwide sea level rise threatens many millions
of urban people, especially in poor countries that
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making initial reconnaissance surveys to select
suitable sites for urban development within a
region or a country;
