Environmental Engineering Reference
In-Depth Information
plain give rise, respectively, to prevalent phenomena of
debris flow
or
flood
. These effects are associated with the following: large reductions in
density and consequently of the draining sections of the natural
river
hydrographic network
; the incorrect sizing of the openings of the bridges
and drainage tunnels; excessive and/or “casual” use of subways that are
almost devoid of adequate drainage and underground works designed to
protect them from the surface water affecting them; the creation of reliefs
that slow down (or prevent) natural surface drainage of water and which,
furthermore, promote the deposition of sandy-loamy materials transported
by them, thus waterproofing soils, with the consequent elimination of
underground water drainage; and the almost systematic lack of mainte-
nance of drainage systems.
To the underground cavities, either natural or of anthropogenic origin,
are often associated phenomena of failure or collapse of artifacts. The pres-
ence of natural underground cavities, typical of rocks sensitive to karst
processes, may be assumed from the careful analysis of a detailed geologi-
cal map, while the presence of anthropogenic underground cavities, achiev-
able on different lithotypes, can be known only through oral or historical
testimony.
Significant progress has been made on the knowledge of the activation
and evolutionary control factors of the different types of hazard mentioned
previously, allowing the zoning of geoenvironmental hazards to be carried
out with considerable confidence, but there are still unresolved problems
related to the temporal prediction of events.
The technique is different depending on the type of
risk
, and always
provides a deeply detailed geological-technical study of the territory, sup-
ported by historical, geophysical, and geomechanical investigations and by
possible installation of monitoring systems. The purpose is to check
whether the anthropogenic (or other) “structure” falls within the “firing
range” of the process under consideration or in areas where it can signifi-
cantly feel its effects.
To do this, we must have a thorough knowledge of the lithotechnical
characteristics of the land forming the foundation of the structure and the
hydrogeomorphological characteristics
of the site and of an adequate
surrounding area. With a good approximation of the magnitude of the phe-
nomenon, it is possible to move on to engineering analyses, designed to
assess the likelihood that the anthropic structure fulfills the necessary
requirements to withstand the stress caused by the process.
The analysis of geoenvironmental risks is both essential and a priority
for any action of spatial planning aimed at improving the socio-economic
conditions of citizens, for whom
geoenvironmental security
is of “vital”
importance.
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