Riprap is stacked in front of buildings.


By Steve Lundeberg, OSU news writer

Tillamook County’s risk of flooding and erosion may be more closely tied to development policies than to climate change, suggests new research partly funded by Oregon Sea Grant.

“Our modeling results suggest that adaptation policies implemented in response to coastal hazards will have a greater impact on community exposure than climate change,” said Peter Ruggiero, a professor in Oregon State University’s College of Earth, Ocean, and Atmospheric Sciences.

He and John Bolte, the chair of OSU’s biological and ecological engineering program, led the study, which was published in the journal Water. They used a computer modeling platform known as Envision to see how flooding and erosion might affect buildings and access to beaches in Tillamook County through the remainder of the 21st century.

Although the findings are based on simulations in Tillamook County, some of the results “are generalizable to the Pacific Northwest and some may be useful to communities in other parts of the country,” Ruggiero said.

Using data from Tillamook County, which is along the northern Oregon coast, the researchers entered into Envision information on:

  • landscape characteristics
  • population growth
  • development
  • water level
  • coastal change models
  • policy scenarios
  • climate change scenarios (e.g., changes in sea level, wave height, and El Nino frequency)

The model considered the following four policy scenarios:

  • continuing current development policies
  • implementing policies that involve resisting environmental change to preserve existing infrastructure and human activities
  • implementing policies that involve shifting development to suit the changing environment (e.g., managed retreat)
  • relaxing current policies such that existing buildings and infrastructure and new development take precedence over protecting coastal resources, beach access, scenic views, recreational use and public rights

The most important takeaway, Ruggiero said, was the power of adaptation policies to positively or negatively affect a coastal community’s exposure to the impacts of flooding and erosion. 

Those policies include:

  • constructing protective structures between the beach face and the shoreline
  • adding sediment to beaches where access in front of those structures has been lost
  • removing or relocating buildings repeatedly affected by coastal hazards and turning hazard zones into conservation areas
  • constructing new buildings well above the base flood elevation established by the Federal Emergency Management Agency
  • preventing new development in hazard zones even if those areas are within urban growth boundaries

“The combination of climate change and development pressures has the potential to significantly increase the effects of flooding and erosion on coastal populations,” Ruggiero said. “The strategies used to adapt to these impacts have the potential to either improve or exacerbate exposure to hazards.”

The National Oceanic and Atmospheric Administration was the other funder on the project. Former OSU graduate students Alexis Mills, Katherine Serafin and Eva Lipiec were additional co-authors.