Scientists are continually refining their understanding of the potentially catastrophic forces of earthquakes and tsunamis, as well as the more gradual effects of climate change on the coast. The vulnerability of coastal communities to chronic and catastrophic forces is a concern to those who live, work, and recreate in those communities, and to public officials responsible for community safety and well-being. These natural hazards and their impacts can be magnified by the coastal environment. For this reason, coastal hazards are called out specifically in the Oregon NHMP.
There are two kinds of coastal hazards, catastrophic and chronic. Catastrophic hazards are regional in scale and scope, such as the massive Cascadia Subduction Zone earthquakes with severe ground shaking, subsidence, landsliding, liquefaction, and tsunamis. Catastrophic events are inherently difficult to predict and have only recently become a principal concern for coastal communities.
Chronic hazards are more local in occurrence and impact, are usually present over the course of a year, and may result in damage to life and property that, although sometimes dramatic, is limited in scope and severity. Chronic hazards include river and ocean flooding from storms, bluff and beach erosion, landslides on steep slopes, or windstorms. The wide distribution and frequent occurrence of chronic hazards make them a more immediate concern.
There are many dangers inherent in living on the coast. While coastal bluffs gradually erode over the long-term, they can also respond very rapidly, at times sliding away (in a matter of minutes to a few hours) so that homes and sections of highways are damaged or destroyed. Beaches are especially dynamic features, as sand is constantly shifted about. This is especially noticeable in major storms, with the shoreline retreating rapidly, periodically destroying homes built close to the sea. At other times, large quantities of sand migrate back onto beaches, burying homes built atop coastal dunes. There is no location on the Oregon coast that is immune to coastal hazards.
Without question, the most important natural variables that influence changes to the shape and width of the beach and ultimately its stability are the beach sand budget (balance of sand entering and leaving the system) and the processes (waves, currents, tides, and wind) that drive the changes.
Human influences associated with jetty construction, dredging practices, coastal engineering, and the introduction of non-native dune grasses have all affected the shape and configuration of the beach, including the volume of sand on a number of Oregon's beaches, ultimately influencing the stability or instability of these beaches.
Planning for Coastal Erosion
Cities and counties are required to account for areas subject to natural hazards in comprehensive plans and associated ordinances. On the coast, planning for coastal hazards is guided by Statewide Planning Goal 17: Coastal Shorelands; Goal 18: Beaches and Dunes; and Goal 7: Areas Subject to Natural Hazards (which covers earthquake and tsunami). These goals require local governments to identify and plan for the dynamic and potentially hazardous nature of coastal areas, particularly along the ocean.
Goal 17: Coastal Shorelands
The purpose of Goal 17 is "to conserve, protect, develop, and, where appropriate, restore the resources and benefits of all coastal shorelands." In addition to its conservation objectives for protecting various shoreland habitats, Goal 17 aims to reduce hazards to human life and property.
Local governments are required to delineate a Coastal Shoreland Planning Area that includes lands subject to ocean flooding and within 100' of the ocean shore or within 50' of an estuary or coastal lake, and adjacent to areas of geologic instability related to or impacting a coastal water body.
Goal 18: Beaches and Dunes
Goal 18 is designed "to conserve, protect, and where appropriate, develop, and restore the resources and benefits of coastal beach and dune areas." The goal also aims to reduce hazards to human life and property from natural or human-induced actions associated with these areas.
Areas subject to Goal 18 include beaches, active dune forms, recently stabilized dune forms, older stabilized dune forms and interdune forms. Uses shall be based on the capabilities and limitations of beach and dune areas to sustain different levels of use or development, and the need to protect areas of critical environmental concern, areas having scenic, scientific, or biological importance, and significant wildlife habitat as identified through application of Goal 5 (Natural Resources) and Goal 17 (Coastal Shorelands).
Local governments are required to inventory beaches and dunes and describe the stability, movement, groundwater resource, hazards and values of the beach, dune, and interdune areas. Local governments must then apply appropriate beach and dune policies for use.
Coastal Hazards Resources