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Predicting floods in the Pacific Northwest

Oregon’s coast Oregon’s coast Sascha Burkard
08 Apr
2015
The Pacific North West’s isolated, low-lying cities are at risk from stronger storm surges

Cities in the Pacific North West, such as Seattle and Vancouver, tend to be coastal population clusters, making them especially vulnerable to storm surges that are expected to increase due to climate change, according to new research.

Unlike the South and East coasts of the US, coastal flooding in the Pacific Northwest comes mainly from large waves generated by storms rather than hurricanes.

‘We get big storms here, it’s not uncommon to see wave heights that are ten metres,’ says David Hill, a researcher at Oregon State University. ‘Those waves do a couple of things. They can overtop dunes and sea walls. There is also a curious effect where as those waves approach the shores and break, they can actually push the water up, creating a storm surge effect.’

A storm surge is an abnormal rise of water generated by a storm, which causes extreme flooding in coastal waters.

The research into the Pacific North West looked at trends over the decades until the century’s end. Data direct from IPCC was used in the research, modelling all the components that can cause flooding including waves, tides and wind.

‘The models that we need to simulate year after year of climate data are computationally intensive. They solve key physical equations that govern the transport of water and energy, which requires a fine grid in space and time,’ says Hill.

The findings were overlaid on a digital model to identify inundation zones. Oregon city planners will need to reconsider flood maps, based on the new data. Hill found that flood levels will vary considerably over different areas, a fact not taken into account in current flood maps.

There’s also more at work than just sea level rise, according to the research. Waves and tides will be amplified in the future.

This research was published in The Journal of Geophysical Research

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