Some perspectives on geological hazards

The importance of geological disasters ranks with with meteorological disasters on a global scale. Although available data are of limited quality it appears that geological disasters are far less frequent, kill twice as many people per event, produce more damage, but are less widely covered by insurance—suggesting that the victims are affected more severely.

Hazard pairing is too often ignored but mapping programs need to recognise that geological hazards frequently occur together, that a wide variety of types of hazards and consequences may stem from one event, and that equivalencies of risk must be established between hazards before hazard or consequence maps will achieve their full potential for planners and administrators.

Extreme events, with frequencies of about 1 in 10,000 years, are rarely considered by those interested in geological hazards though action has already been taken in some parts of the world to reduce the effects of floods with similar return periods. Examples of eruptions and tsunamis suggest that such infrequent geological events need to be at least included in worst-case scenarios. Several lines of evidence suggest that future disasters resulting from geological hazards are likely to be worse than those experienced so far this century.