| Shoreland Processes and Hazards |
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| Introduction |
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Oregon’s ocean shore is subject to a wide range of geologic forces and climatic conditions that continually shape the coast and put life and property at risk. As development progresses into steeper slopes, ocean bluffs, and dune areas, the level of risk increases, as does the need to make better decisions about where to build and what to do to protect existing development.
Climatic conditions, sea level rise, storms and cyclical events such as El Niño exacerbate chronic ocean shore erosion problems, resulting in dramatic losses of beach and property and heightening the focus on hazard issues. 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.
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| What are Coastal Hazards? |
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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.
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| Planning and Regulation |
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As a part of the comprehensive planning process, cities and counties must address areas with natural hazards. Statewide Planning Goals 17 and 18 direct local governments to address natural coastal hazards in their comprehensive plans through inventory and implementation requirements. Ocean shore development permit authority resides with the Oregon Parks and Recreation Department.
Goal 17: Coastal Shorelands
The purpose of Goal 17 (pdf) is to conserve, protect, develop, and, where appropriate, restore the resources and benefits of all coastal shorelands. In addition, Goal 17 aims to reduce hazard to human life and property. Goal 17 provides for the protection of major marshes, significant wildlife habitat, coastal headlands, and exceptional aesthetic resources included in community inventories. Coastal shoreland inventories are required to identify and provide information on the nature and location of areas subject to geologic and hydrologic hazards within the designated coastal shorelands planning area. These areas include 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 (pdf) is designed to conserve, protect, where appropriate develop, and, where appropriate, restore the resources and benefits of coastal beach and dune areas. The goal also aims to reduce the hazard to human life and property from natural or human-induced actions associated with these areas. Coastal areas subject to this goal 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 Goals 5 and 17.
Inventories are required to identify and designate beach and dune uses and policies. The inventories describe the stability, movement, groundwater resource, hazards and values of the beach and dune areas. These areas include beaches, dune and interdune forms.
Ocean Shore Regulation
The Oregon Parks and Recreation Department [OPRD] is responsible for protecting the scenic, recreational, and natural resource values of the Oregon coast. OPRD accomplishes this goal through an extensive permitting program for shoreline protection under the authority of The Ocean Shore Law [ORS 390.605 – 390.770], also known as the "Beach Bill." OPRD regulates activities affecting the ocean shorelands west of the statutory vegetation line, the survey line, or the line of established vegetation which is most landward. The OPRD recently incorporated the Department of State Lands authority to regulate removal and fill activities along the ocean shore under their permit program. Activities permitted under these regulations are required to be consistent with the Statewide Planning Goals and corresponding provisions of local comprehensive plans.
Tsunami Inundation Zones
Under the authority of ORS 516.090, the Department of Geology and Mineral Industries [DOGAMI] has mapped tsunami inundation zones in coastal communities. The maps should be used by local governments for the purpose of developing evacuation routes and to identify areas where the development of certain critical and essential facilities and major structures are restricted, in accordance with ORS 455.446 and .447. There are exemptions for existing facilities and water dependent development as well as exemptions for certain facilities based on need for strategic location or school district boundaries. Local governments work with DOGAMI to create maps and develop evacuation routes.
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| What OCMP is Doing |
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The OCMP has a multi-year strategy to enhance coastal hazards management by a series of projects and work tasks to improve hazard policies, assessment and education. In 1994, the OCMP, along with other stakeholders involved in the Coastal Natural Hazards Policy Working Group, conducted a broad review and analysis of coastal hazards management at the state and local levels. Using an "all-hazards, all-decisions" approach, they evaluated the effectiveness of existing policy and policy implementation. The group identified 23 coastal hazards issues and 79 recommendations for improved policies and practices in the areas of hazard assessment, land use, shore protection and emergency response. They then published the recommendations in a report entitled "Improving Natural Hazards Management on the Oregon Coast" [available from Oregon Sea Grant Publications [.pdf - 3.8 MB] [HTML - 319 KB]]. Those recommendations have resulted in a series of projects and work tasks that are continually being carried out as financial and staff resources allow.
Generally speaking, there are a series of policies and tools that coastal communities may adopt to mitigate the risk they face from coastal hazards. Improved siting, design, and construction standards would reduce the risk to new development in an identified hazard area.
For existing development additional methods for coastal hazard mitigation include soft stabilization and hard stabilization techniques. Soft stabilization techniques enhance the inherent buffering capabilities of the shoreline while hard stabilization techniques attempt to permanently fix the position of the shoreline, thus reducing the effects of wave attack. Indirect approaches to coastal hazard mitigation include education programs and natural resource protection laws. These practices are applicable along any type of shoreline and serve to both educate coastal landowners and preserve the natural environment.
Hazard Assessment
The OCMP and its state agency partners have undertaken a variety of projects to improve the level of data and information on coastal hazards. A pilot chronic hazards mapping project and shoreline stability database was completed for a 50-kilometer area in Lincoln County [Salmon River to Seal Rocks] by DOGAMI, with DLCD funding. A pilot catastrophic hazards mapping project of the Siletz Bay area was completed and published by DOGAMI, with DLCD funding. Tsunamis and other earthquake related hazards, including areas susceptible to soil liquefaction, soil amplification, and severe ground shaking, were mapped for the pilot project area in Lincoln County.
With the assistance of Oregon State University researchers and others, geometric and numerical models of foredune erosion have been developed and tested. The models allow planners to numerically evaluate ocean processes and sediment transport that cause beach and foredune erosion and provide information that can be used to determine how oceanfront construction setbacks should be established in dune backed beach environments.
Hazard Mitigation
DLCD analyzed the contents of geotechnical reports and developed a set of guidelines for the preparation of technical reports related to the impacts of coastal erosion. These guidelines were used by the Department to prepare a model ordinance for local government use and are being used in concert with other hazard mitigation project and mapping projects. A report of the Coastal Hazards Alleviation Techniques [ACHAT] (pdf) applicable to the Oregon coast was prepared for use by local governments in assessing natural hazards mitigation options.
Littoral Cell Management Planning
A littoral cell management plan is a comprehensive, integrated, area-wide hazards management strategy unique to different physical and social settings found along the Oregon coast. It is focused on the reduction of risk to new and existing oceanfront development from chronic coastal natural hazards. A littoral cell management plan should include: littoral cell inventories, a chronic hazards management strategy, and implementing mechanisms. See our "Special Projects" page for more information.
Oceanfront Construction Setbacks
An oceanfront construction setback methodology which considers the full range of geologic and oceanographic factors affecting shoreline stability on the Oregon coast was developed and field-tested.
Hazard Education
Coastal Earthquakes and Tsunamis, Reducing the Risk: Regional Conference. A three-state regional conference was produced by OSU Sea Grant Extension and DLCD to disseminate current scientific information on Cascadia Subduction Zone earthquakes. Experts shared the results of recent coastal hazards reduction projects, and identified and discussed management and policy options to reduce the risks to coastal communities from a major earthquake and tsunami.
Future Work
Coastal Development Handbook. A coastal development handbook for the Oregon coast is being developed on coastal process and hazards, beach and shoreland public policy, buying oceanfront property [what to look for, what questions to ask], building on oceanfront property, choosing appropriate hazard mitigation techniques, choosing and using geotechnical consultants and engineers. Expected publication date is June 2001. Some of the factors that affect our ability to improve the effectiveness of managing development in potentially hazardous locations are increasing development pressures and significantly higher property values on the coast. Ironically, some of the most potentially hazardous properties are also the most desirable because of location or views.
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| Additional Resources |
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Listed here are contacts, programs, and documents to assist planners, local governments and citizens in obtaining further information on coastal hazards.
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