00:00The sinking of land due to natural and man-made causes, a phenomenon known as subsidence,
00:12is pushing an increasing number of people into flood zones.
00:16Subsidence is a natural phenomenon linked to movements of tectonic plates or to the
00:21accumulation of sedimentary layers in shallow basins, but the phenomenon has accelerated
00:26due to human factors.
00:29The weight of buildings, for instance, and also the weakening of soils caused by the
00:34development of underground infrastructure, vibrations from road traffic, extraction of
00:39minerals and especially unregulated pumping of underground water from aquifers.
00:45An aquifer is an underground layer of porous and permeable rock containing water which
00:50provides a natural support to urban zones, where some big cities are sinking by over
00:5525 centimetres per year.
00:58The artificial covering of soils with, for example, bitumen and concrete, make the surface
01:03impermeable, preventing the refilling of underground water sources by rainwater, which further
01:09weakens this natural support.
01:11But the phenomenon of subsidence can be contained if timely action is taken.
01:16Cities can limit the artificial covering of surface soil, limit urban concentration or
01:20ban pumping from aquifers and by providing alternative water sources.
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