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INTRODUCTION i Man is periodically confronted by a variety of hazardous phenomena, some of which result from his own activities, and others that are rela- ted to the normal processes of nature. These natural hazards vary in both their frequency of occurrence and degree of severity. For example, Gulf Coast residents face the yearly threat of hurricanes, whereas de- structive floods are a fairly remote danger in most parts of the country; areas with steep slopes and evidence of previous landslides are likely to be more dangerous development sites than steep terrain where soil creep is the dominant process. This suggests that sensible responses of indi- viduals and society to such natural phenomena should take account of the complementary elements of severity and likelihood. Unfortunately, the formalization of those rather simple concepts in the techniques and analytical methods of engineering, planning and other supporting disciplines has shrouded the decision-making process in an aura of scientific and technological elegance. In other words, the re- sultant strategies, which generally combine elements of control, accomo- dation or avoidance, are commonly perceived by laymen as deterministic, precise and without significant error. Actually, the methods are often probabilistic and may contain extensive approximations, safety factors and professional judgment. The public sometimes seems inclined to re- linquish its participatory role in decision-making to the experts, per- haps for reasons of apathy or lack of understanding. This is potentially dangerous, however, because the ultimate decisions regarding natural haz- ards do not depend solely upon scientific and technical objectivity. Substantial economic and political pressures are exerted which mayor may not be in the best interests of the general public. It is indeed