Researchers study coastal hazards

CORVALLIS, ORE.—Researchers at Oregon State University (OSU) are studying why wave heights in the Pacific Ocean have been increasing in recent years and how this phenomenon—coupled with global warming—might affect coastal erosion, flooding, and development along the Pacific Northwest coast. Peter Ruggiero, an assistant professor of geosciences at OSU, is developing new computer models that factor in the increasing wave heights, as well as rising sea levels and the potential increase in frequency of El Niño weather conditions. El Nino is a cyclic water temperature weather pattern that results in warmer-than-normal ocean temperatures and triggers larger storms in the Pacific Ocean.

"We’re trying to see how a combination of these different processes—bigger waves, higher sea levels, and potentially more frequent and intense El Niño conditions—could affect coastal areas along the Pacific Coast in a range of ways, from coastal erosion and lowland flooding to planned development," said Ruggiero, whose research is funded in part by a $190,000 grant from Oregon Sea Grant at OSU.

"If you’re thinking only about sea level rise, you’re missing the boat," Ruggiero said. "When we combine all these processes, the probability of waves overtopping a dune or banging into a sea cliff is three to 10 times greater than models that use only sea level rise projections."

Ruggiero’s colleagues, Paul Komar, an emeritus professor in the OSU College of Oceanic and Atmospheric Sciences, and Jonathan Allan, of the Oregon Department of Geology and Mineral Industries, have been documenting observed wave heights in the Pacific Ocean for the last 30 years. Their research shows that the average wave height has increased more than 15.7 inches during that time, and the average wave height of the five largest winter storms per year is increasing at a rate of as many as 2.75 inches per year.

"There has not been a lot of research into what’s causing this increase in wave heights," said Ruggiero. "But the data clearly shows it’s happening. And if this trend continues, we need to know what we’re up against, and what the relative impact on the outer coast will be. My preliminary research is showing that increased wave heights definitely play a significant role in the frequency and magnitude of coastal hazards such as erosion and flooding, so now we need to be figuring out the physics."

The project is extremely complicated, however, because landforms and sand at the outer coast are constantly rearranging themselves, said Ruggiero, who has been doing research on a section of coastline near Long Beach, Wash., where one part of the beach is retreating 16 to 32 feet each year, but another part is being built up. Wave run-up, or the thin layer of water that slides up onto the beach after a wave breaks and washes ashore, has been increasing faster in the Pacific Northwest than sea level rise during the past three decades, Ruggiero said. And nobody knows for sure exactly how global warming will affect sea level, El Niño patterns, and wave heights.

The computer models and data Ruggiero’s team are developing could become valuable tools for planners, who work with 20-year-old inundation maps created by the Federal Emergency Management Agency before global warming and sea level rise were issues.

"Our ultimate goal is to develop products that coastal decision-makers can use with regard to planned development and evacuation procedures in coastal areas," Ruggiero said. "You have the majority of the world’s population living within 50 miles of a coast. The more (hurricane) Ikes and Indian Ocean tsunamis happen, the more attention coastal hazards will get, and unless something drastically changes, these situations are going to get worse."