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NATURAL HAZARDS: WHAT ARE THEY, CAN THEY BE PREDICTED, AND CAN THEY
BE PREVENTED? 11
present effects of global warming may represent another such change in natural
conditions, fuelled by anthropogenic activity, which has the effect of accelerating
natural processes.
Natural Hazards in Norway
As seen from the ongoing risk assessment of natural hazards in Norway the major
risks seem to be associated with the geological and the hydrological cycles (reference
this volume). Rockfalls and large landslides, due to their relatively high frequency
and some recent events that had disastrous consequences (e.g. Lodalen; Nesdal 1998),
these are considered the most likely natural hazards to occur also in the future, and
are given much attention (e.g. Blikra, this volume).
As human beings, we are used to Mother Earth providing a solid and stable
substratum under our feet, and when this fundamental circumstance fails, like in an
earthquake or a great landslide caused by quick clay, it is particularly scary. Due to
the relatively high frequency of large landslides and rockfalls, the Norwegian
population is to some degree accustomed to such events and are able to relate to them,
even though the consequences can be huge (Blikra this volume). Being situated far
from active tectonic plate boundaries, we are less accustomed to other geological
hazards like earthquakes. Still, such events do occur in the Norwegian mainland and
in the Norwegian continental shelf, although both frequency and magnitude are very
moderate (Ramberg et al. 2008). Regularly occurring micro-earthquakes do,
however, indicate that some larger seismic events may occur in the future (cf. the
Oslo earthquake 1904). It would probably be irresponsible entirely to avoid
estimating the risk potential and the consequences of such events in the most densely
populated regions of Norway, despite their infrequency.
The Acceptance of Natural Hazards
Because natural hazards are associated with the principal forces and processes on
our planet, some philosophical/political aspects can sometimes arise when dealing
with them. A simple example is the annual problem of flooding: Is it most convenient
to solve the problem of flooding by constructing defences that completely prevent
water from leaving the river channel but thereby perhaps increasing water levels
downstream, or is it better in the long run to find a (sustainable) balance point in the
water budget that can be handled locally? This balance point also affects the risk
element in warnings: People who are persuaded or even forced to leave their homes
may be less willing to do so if the warnings are not correct e.g. in cases where a
predicted rock fall or earthquake does not happen (e.g. Blikra this volume). This
requires that the political authorities and the populace understand and accept risk
assessments, which may sometimes be very challenging (e.g. Nur 2008).
Natural hazards represent a challenge to humanity and we are perhaps
approaching a threshold to a period of enhanced risk affiliated with global climate
change. As always, the most vulnerable part of the human population are those who