Geoscience Reference
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a concentration of people in urban cities and delcining rural population
—people in search of better jobs (to make more money) and small farmers
(either they have lost their lands to big farms or cannot compete with
mechanization of large farms) are moving to cities. However, because of
this mass migration, cities are becoming populated and there is a lack space
for further development. This is giving rise to either illegal settlements or
occupation of fragile land (such as hill sides) by low-income strata group
in a disorderly urban concentration areas known as slums.
Within the context of social actions needed in areas of low income
include: projects involving slum upgrading projects that involve integration
of social services for the weaker socio-economic communities; survey of
the lack of urban infrastructure (sanitation, transportation, education, etc.),
their needs for cultural and social activities and eliminating risks (such as
geological or geotechnical in character and include the houses with low
structural stability).
The mapping, characterization and prioritization of geological and
geotechnical risks in slums and informal settlements including risk of low
stability houses in the slums are discussed next.
Currently, slums are the possible alternative housing for a signifi cant
proportion of the population of large cities. Since immigrants settle in
the empty urban areas left behind in the process of growth of the city,
the conditions in slums are unfavorable and are on fragile land which is
vulnerable due to erosion and have higher risk of mud/land slides and
fl ooding (especially along the rivers). Most of the time, disjointed specifi c
programs are impelemted after an accident (e.g., landslide) but this is not
enough to prevent further disasters. It is necessary to act in a planned way,
using preventive interventions with multiple, integrated and prioritized
through a rational system of risk control (Carvalho 1994).
The geotechnical risk situations are often related to human intervention,
but may be aggravated or even due to the unfavorable geological
characteristics for human occupation in a particular location. In this sense,
the mapping of geotechnical risk situations is the starting point for an
adequate planning of interventions required. The goal of this activity is the
development of a comprehensive diagnosis of geotechnical risk situations.
Such risk situations may be associated with areas of slopes (including
massive landslides on and/or cut slopes in natural soil, landslides in
landfi lls, the outbreak of erosion, falling blocks, etc.) or the low areas
(including undermining the foundations of houses and/or restraints built
along by the stream, rupture of embankments on soft soils, erosion of
embankments, etc.). It is proposed, according to the recommendations made
by UNDRO 1991, that this diagnosis is carried out on two scales:
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