OSU engineer is studying estuary flooding in the Coos Bay estuary (pictured here) and the Tillamook Bay estuary.

New research suggests that intense storms could increase the impact of flooding in coastal estuaries. As more water is forced into the estuary, site-specific geographic features will cause more inundation in some parts of the estuary than others, contrary to the uniform rise that was previously expected.

Estuaries are mixing pots between rivers and the ocean – and also tend to be hotspots for human development. Tumultuous offshore waves that break during winter storms force water up into the estuary, causing it to inundate surrounding areas.

David Hill, a coastal engineer at Oregon State University, is studying how to more effectively measure the effects of flooding in estuaries along the Oregon coast.

“In Oregon, estuaries really represent a concentration of a great number of things,” Hill explained. “A concentration of infrastructure and a concentration of commerce. If you look where the population is, it’s all near estuaries.”

Historically, coastal managers have simply drawn a uniform circle around an estuary on a map to estimate flooding, and raised or lowered the line depending on predicted changes in water level. This method, although easy, neglects the complicated physics that take place in such environments.

Hill used historical storm data and future climate predictions to simulate the effect of storms on the Tillamook Bay estuary. His detailed models discovered that not all parts of an estuary are created equal.

“One thing that we found is that inside a large body of water like Tillamook Bay, there can be noticeable differences from one location to another. So the water levels in the whole bay are not the same. The northern part of the bay is more susceptible to higher water levels than the southern part.”

This new information is causing state flood maps to be updated and flood zones reevaluated. Hill says he is looking forward to working directly with coastal communities to find out what information is most useful in their planning.

Waves breaking offshore force water up into the estuary and cause flooding.

“A big part of this project is wanting to actually connect with organizations within our study sites. They’re the ones that have the best idea of what kind of information is valuable to them and that they need to do short term and long term planning.”

The project is only six months into a two-year cycle funding and already two papers are close to being published; one paper is in press with the Journal of Coastal Research, and the second is in re-review with another journal.

While Hill is focused on the impact to coastal infrastructure, OSU ecologist Sally Hacker is researching what effect inundation will have on eelgrass habitat in the estuaries.

“Eelgrass is a critical habitat for commercially important fish and crabs,” Hacker explained. “We will be using models to project the extent of eelgrass under future sea level elevations.”

Hacker will incorporate Hill’s data into her models to better predict ecosystem changes along the coast.

Scientists say it is likely that storm events will become more frequent and more powerful in the future. Understanding the economic and ecological impacts of flooding will help coastal communities adapt in an ever-changing climate.

Learn more:

• Preparing for Climate Change in Oregon Estuaries: Flooding, Ecological Impacts, and an Integrated Approach toward Adaptive Management (Dr. Hill’s current Sea Grant-funded research project