NATURAL DISASTER is an event in which human systems in a particular area and at a particular time have been severely disrupted due to the impact of a naturally occurring earth process defined as a geohazard. The magnitude of the impact and its severity are highly variable.
RESPONSE TO GEOHAZARDS includes all the measures and strategies that are used to reduce the negative impact of natural events. Following Alexander (1993). A hazard may be regarded as the predisaster situation, in which some risk of disaster exists, principally because human population has placed itself in a situation of vulnerability. When the risk becomes tangible and impending, there is distinct threat of disaster. Hence, the sequence of states pertaining to disaster is as follows:
Hazard - risk - threat- disaster (impact) - aftermath.
In Jamaica, land-use decisions must be based on accurate hazard information and risk assessment. In order to do a better quantification of the risk from natural processes and defining "acceptable risk," the geologists need to produce hazard zonation and risk maps which must be based on good science. These maps show division of land surface in a particular area into subareas and the ranking of these subareas according to degrees of actual or potential hazard from a specific hazardous condition, for example landslides. Mitigation, that is, reducing the severity, is to be based on the availability of hazard zonation maps. Acceptable risk is the level of risk that is acceptable to the society and it is elastic standard. If the society has a poor knowledge of a particular hazard and its impact, the acceptable risk may be high. However, a well-informed society demands that it remains less affected by the extreme natural events and tends to adapt itself to the natural physical environment.
Mitigation could be either structural or non-structural (Alexander, 1993)
Structural methods involve retrofitting of existing structures and reinforcement of new structures using civil engineering techniques. Safety features are provided so that the buildings, houses and infrastructures (roads, bridges, ship docks, and runways) may be able to withstand extreme natural events. These techniques are, however, very expensive.
Non- structural methods are:
a. Short-term which include emergency plans, evacuation plans, prediction of impact and warning processes.
b. Long-term which include building codes, construction norms, hazard micro zonation for all risks (multiple hazards) and selected risks, land-use control (regulations, prohibitions, moratoria, compulsory purchase), probabilistic risk analysis, insurance, taxation, education and training.