Dynamic geologic processes of crustal uplift and subsidence, earthquakes, and volcanic activity are potentially catastrophic forces that are also constantly present - though they occur over a longer time period. These forces have been causing dramatic changes in the coastal landscape long before humans settled and developed along the ocean shore. The vulnerability of coastal communities to the chronic and catastrophic forces at work is a continual concern to those who live, work, and recreate in those communities. And to the community managers. There are two general categories of coastal hazards.
Catastrophic hazards are regional in scale and scope.
Cascadia Subduction Zone earthquakes, and the ground shaking, subsidence, landsliding, liquefaction, and tsunamis that accompany them, fall into the category of catastrophic hazards. Chronic hazards are local in nature, and the threats to human life and property that arise from them are generally less severe than those associated with catastrophic hazards. The wide distribution and frequent occurrence of chronic hazards makes them a more immediate concern. Due to the relative uncertainty and infrequency of catastrophic events, Oregon coastal communities generally focus planning efforts on the chronic coastal hazards of flooding, erosion, and landslides. The damage they cause is usually gradual and cumulative.