Environmental Engineering Reference
In-Depth Information
8.6.3
Geomorphology of Places and Hydrogeological Risk
Bernardino Gentili
The presence, quality, and quantity of numerous natural resources are
closely linked to the geological characteristics of the territory, but so too
are different conditions of geoenvironmental hazard, which are connected
to high-level risks. These depend: (1) directly on the geodynamic evolution
of the Earth's crust, as in the case of seismic and volcanic risk (“geological
risk”); and (2) on the interaction between geological and climatic condi-
tions, as in the case of “
hydrogeological risk
.”
Geological studies
have always given precedence to analyses concern-
ing natural environments and, as a rule, have more or less avoided intense-
ly humanized ones, particularly urban areas, because man has changed the
original structure, at least as regards the most superficial levels of the
Earth's crust.
However, given that there is no work or human activity that does not
have relationships (more or less close) with rocks and earth, in recent times
(particularly in the last three decades), the need to extend geological stud-
ies even to urban areas, with emphasis on aspects related to application, has
been felt with gradually increasing intensity. Specific research programs
aimed at adjusting operational methods have been developed to apply to:
(1) the definition of the natural geological model of the urban substrate;
and (2) the recognition of the changes introduced by humans in the
geolog-
ical structure
and the correct definition of their impact on the physical
environment [1, 2].
8.6.3.1 Hydrogeological Risk
In this area, the research on the mass movements that in “young” countries,
geologically speaking (e.g., Italy), are responsible for the largest number of
casualties and environmental damage after earthquakes, is of primary
importance.
Historical urban centers located on the top of mountains appear to be
particularly vulnerable to mass movements; this situation is far more com-
mon in territories of older urbanization, because they are “attacked” by the
upstream regression of the phenomena which are generally activated at
lower altitudes; the instabilities are generally slow or very slow-moving.
This is not the situation of towns located at the foot of the slopes or in an
intermediate position: they are generally subject to the mainly disastrous
impact of fast-moving masses.
Other hazards of noteworthy importance are linked to the action of sur-
face water and groundwater. The first is often associated with fluvio-torren-
tial processes, which in urban areas located at the foot of a slope or in a
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