ABSTRACT
All lands on earth are subject to natural hazards, such as, floods, droughts, landslides, earthquakes, typhoons, volcanism, etc. The hazard itself cannot be prevented, but through an understanding of the land conditions which are prone to a given hazard and the processes which could culminate in damage to life and property, it is possible to minimize the damage to life and property, through preparedness for a particular eventuality. For instance, Bangladesh and the province of Florida in USA, are highly susceptible to hurricanes. But the number of deaths per million of population in Florida due to hurricanes is much less than in Bangladesh, because of the prevalence of more efficient systems of preparedness and crisis management. Natural Hazard (H) is probability of occurrence, within a specified period of time
and within a given area, of potentially damaging phenomenon (e.g. landslide). Vulnerability (V) is the degree of loss (or damage) resulting from H, of a given magnitude, expressed on a scale from 0 (no damage) to 1 (total loss). Specific risk (Rs) is the expected degree of loss due to particular, H. Elements at risk (E) are the population, properties, and economic activities, including public services at risk in a given area. Total risk (Rt) is the expected number of lives lost, persons injured, damage to property, or decline of economic activity due to a particular, H (Carrara, 1984). Thus,
Rs = H × V ; Rt = E× Rs = E×H × V
The general model of management response to a hazard event is given in Fig. 6.1.1. A geological hazard is a geological condition, process or a potential event that poses
a threat to the health, safety and welfare of a group of citizens, or the functions or economy of a community or a larger governmental entity (US Geological Survey, 1977). The spectrum of hazards is quite large. Hazards may arise from natural or
technological causes. Hazardous conditions set the stage for future harm. It is therefore necessary to recognize how certain conditions of land when acted upon by a particular process, can culminate in perpetuating a particular kind of damage (Tables 6.1.1 and 6.1.2).
