News Release

Report offers framework to guide decisions about Spirit Lake and Toutle River at Mount St. Helens

A new report from NASEM offers a framework to guide federal, tribal, state and local agencies, community groups, and other interested and affected parties in making decisions about the Spirit Lake and Toutle River system, near Mount St. Helens

Peer-Reviewed Publication

National Academies of Sciences, Engineering, and Medicine

WASHINGTON - A new report from the National Academies of Sciences, Engineering, and Medicine offers a framework to guide federal, tribal, state and local agencies, community groups, and other interested and affected parties in making decisions about the Spirit Lake and Toutle River system, near Mount St. Helens in southwest Washington state. The process should include broader participation by groups and parties whose safety, livelihoods, and quality of life are affected by decisions about the lake and river system, the report says.

In addition, updated data are needed to inform decision-making, said the committee that wrote the report. Currently, much of the information that informs long-term management of the system is from the 1980s and 1990s and is incomplete and sometimes outdated. Agencies engaged in risk management of the system should develop a coordinated monitoring system to track changes in factors that affect risk, and the data and analysis should be made available to all. Recent insights about the likelihood of a Cascadia Seismic Zone earthquake affecting the Mount St. Helens vicinity warrant greater examination, the report notes.

"Our report stresses the importance of thinking of Spirit Lake and the Toutle River as a system," said committee chair Gregory Baecher, Glenn L. Martin Institute Professor of Engineering at the University of Maryland, College Park. "Using an analytic process that is also deliberative will help decision-makers identify the many objectives, alternatives, and impacts of those alternatives for managing that system."

The 1980 eruption of Mount St. Helens radically changed the landscape surrounding the volcano in southwest Washington State. The eruption sent an avalanche of debris into the North Fork of the Toutle River and blocked the drainage of Spirit Lake, causing a dangerous rise of lake waters. Should the debris blockage- which is functioning as a dam - fail, 50,000 people could be put at risk of catastrophic flooding and mud flows. The region also suffers from chronic flooding, which is exacerbated by heavy sediment loads coming off the mountain.

In the 1980s, engineering measures were implemented to manage catastrophic and chronic flooding risks - including a tunnel to drain and help manage water levels in Spirit Lake, and a sediment retention structure to prevent sediment from flowing downstream. The tunnel now requires major repairs, and the sediment retention structure is nearing its capacity. In 2015, the U.S. Forest Service asked the National Academies to convene a committee to propose a decision framework to support the long-term management of risks related to the Spirit Lake and Toutle River system.

To guide choices about the lake and river system, the Academies' new report recommends a decision framework grounded in scientific and engineering information, and the use of decision analysis techniques to account for multiple objectives and the values of interested and affected parties. The framework guides the decision-making process through five steps, from clarifying the decision problem to identifying trade-offs among management options.

Early in the decision process, the range of interested and affected groups should be engaged at a depth sufficient for management decisions to be informed by their concerns and values, the report says. Although agencies may already include affected groups in community outreach, the methods of inclusion could be enhanced.

Participants in the decision process may include agencies with authority or interests in the system, those who experience the safety, economic, cultural, or life-quality impacts resulting from management decisions, and those with specialized knowledge related to potential impacts. The number of people participating needs to be small enough that discussions can be of sufficient depth to be meaningful and effective, the report says. In addition to this group, there must be a neutral support team that includes expertise in the technical and scientific fields of concern, decision analysis, stakeholder engagement, and group facilitation.

A framework implementer or lead also needs to be identified to be responsible for applying the collaborative analytic decision-making process. Ideally, the lead would be a new system-level entity or a formal consortium of existing agencies, the report says. The lead would provide a central focus for congressional mandates and appropriations, ensure collaboration across agency and jurisdictional boundaries, and maintain continuous engagement by all interested parties.

It is likely that the first attempt to apply the decision framework will be related to decisions regarding management of water levels in Spirit Lake. As decision participants consider long-term management of the lake, they need to consider a broad set of alternatives, the report says. Options to consider could include, for example, constructing a dry spillway as a backup outlet, or installing a second modern drainage tunnel that would provide redundancy and flexibility. The viability of these and other options is best quantified through an analytic deliberative process as outlined in the report.

Implementing the framework's steps and establishing a common understanding of the lake and river system depends on widely shared, reliable data and analysis, the report says. Monitoring capabilities and data collection need to be updated, and analytic capabilities need to be re-evaluated. Decisions need to be informed by a current characterization of the debris blockage damming the lake, current meteorological trends, a quantification of risks posed by volcanic activity on Spirit Lake water levels, and site-specific quantitative seismic analysis conducted at the debris blockage and the sediment retention structure.

Operational risks - those related to operating engineered structures in the river and lake system - should be explicitly considered when evaluating alternatives for management, the report adds; such risks do not appear to have been systematically considered so far. Examples of operational risk scenarios include rapid lake level rise when the tunnel is closed for repair, and the failure of engineered structures such as the sediment retention structure and levees.

In early 2018, members of the study committee will hold a public briefing in southwest Washington to discuss their findings and recommendations.


The study was funded by the U.S. Department of Agriculture's Forest Service. The National Academies of Sciences, Engineering, and Medicine are private, nonprofit institutions that provide independent, objective analysis and advice to the nation to solve complex problems and inform public policy decisions related to science, technology, and medicine. The National Academies operate under an 1863 congressional charter to the National Academy of Sciences, signed by President Lincoln. For more information, visit

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Andrew Robinson, Media Relations Assistant
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Copies of A Decision Framework for Managing the Spirit Lake and Toutle River System at Mount St. Helens are available from the National Academies Press at or by calling 1-800-624-6242. Reporters may obtain a copy from the Office of News and Public Information (contacts listed above).


Division on Earth and Life Studies
Board on Earth Sciences and Resources
Standing Committee on Geological and Geotechnical Engineering

Committee on Long-Term Management of the Spirit Lake/Toutle River System in Southwest Washington

Gregory B. Baecher1 (chair)
Glenn L. Martin Institute Professor of Engineering
Department of Civil and Environmental Engineering
University of Maryland
College Park

John J. Boland
Professor Emeritus
Department of Geography and Environmental Engineering
Johns Hopkins University

Thomas Dunne2
Professor of Geomorphology and Hydrology
Donald Bren School of Environmental Science and Management
University of California
Santa Barbara

Youssef Hashash
William J. and Elaine F. Hall Professor of Civil and Environmental Engineering
Department of Civil and Environmental Engineering
University of Illinois

John Kupfer
Professor and Chair
Department of Geography, and
Senior Associate Faculty
Environment and Sustainability Program
University of South Carolina

Ning Lu
Department of Civil and Environmental Engineering
Colorado School of Mines

Basil Stumborg
Decision Analysis Expert in Energy Planning and Economic Development
BC Hydro
Vancouver, British Columbia

Kathleen J. Tierney
Professor of Sociology, and
Natural Hazards Research and Applications Information Center
University of Colorado

Desiree D. Tullos
Associate Professor of Water Resources Engineering
Biological and Ecological Engineering Department
College of Agricultural Sciences
Oregon State University

Greg A. Valentine
Department of Geology, and
Center for Geohazards Studies
State University of New York


Sammantha L. Magsino
Staff Officer

1Member, National Academy of Engineering
2Member, National Academy of Sciences

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