Flooding From Hurricanes Worsened by Sea-Level Rise

By Stephanie Paige Ogburn, E&E reporter
12/6/2013 9:37:57 AM

There's an ongoing scientific quest to determine how tropical cyclones will change as a result of climate change, with researchers trying to understand whether such storms will get more frequent or more intense.

Yet while overall there's a fair amount of uncertainty about how such storms will change as the Earth warms, there's another aspect of tropical cyclones and climate change that researchers are more certain about.

That's the fact that sea-level rise and associated shoreline changes will drive flood risks higher from such storms in the future.

A new review paper published in the journal Nature, as part of a special issue on coastal regions, highlights this fact and warns that societies ought to develop ways to adapt to the risk posed by flooding from tropical cyclones.

The beginnings of Superstorm Sandy in Asbury Park, New Jersey. (Credit: Flickr/Anthony Quintano

"I think if we wait, we're going to be in trouble," said Jennifer Irish, a coastal engineer at Virginia Tech and a co-author of the paper. "Not only are there direct impacts [from climate change] because the sea levels are higher, but there is potential for sea-level rise to change shorelines and create a more vulnerable situation for coastal flooding."

Irish and her co-authors, including lead author Jonathan Woodruff of the University of Massachusetts, Amherst, focused their review paper on three important factors relevant to future coastal flooding from hurricanes. One was the changes in tropical cyclones, the second was sea-level rise and the third was shoreline change.

Those last two factors, sea-level rise and shoreline change, are known issues that coastal cities will be experiencing in the future. So it makes sense, the authors write, to invest in projects now that will reduce the impacts from flooding that will be exacerbated by them.

"The era of relatively moderate sea-level rise that most coastlines have experienced during the past few millennia is over, and shorelines are now beginning to adjust to a new boundary condition that in most cases serves to accelerate rates of shoreline retreat," Woodruff said.

A significant amount of research to date has focused on the climate change impacts on tropical cyclones, and the current consensus seems to be that cyclones might be less frequent but possibly more intense, Irish noted.

Shoreline change gets less attention

But less focus has been put on understanding shoreline change, possibly due to less funding devoted to that topic and partly because it's a difficult problem to solve, she said.

"I think it really comes down to we need to understand how sediments are moved around on the coast," she said.

As the review article shows, and as researchers are beginning to understand, sea-level rise will play an important role in the flooding from such storms.

"In our article, we don't mean to say that people haven't been considering sea-level rise. It's just maybe more recently come to light how important sea-level rise is compared to these other factors," Irish said.

Although there is considerable uncertainty about just how much sea-level rise various locales will experience, they can plan to adapt in a modular way. For example, a breakwater might be constructed or augmented with a stronger foundation, so that if it needs to be heightened later, as sea-level rise accelerates in the future, it can, Irish said.

The paper authors noted that coastal areas in developing countries are the most vulnerable, because existing infrastructure is not constructed to deal with such flooding.

But developed countries like the United States also continue to expand and develop on coastlines, which increases vulnerability.

"Most coastal populations are not prepared for an increase in extreme flood frequency," the authors reported.

Reprinted from ClimateWire with permission from Environment & Energy Publishing, LLC. 202-628-6500.

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