Increasing risk of compound flooding for major US cities

 

The number of compound coastal flooding events driven by a combination of both storm surge and heavy precipitation has increased significantly over the past century for many major US coastal cities, find Thomas Wahl and Jens Bender (both University of Siegen) together with scientists of the University of Maine (USA) and the University of South Florida (USA). The study was published online in Nature Climate Change last month.

“Nearly 40% of the US population resides in coastal counties and flooding in these usually low-lying, densely populated and highly developed regions can have wide-ranging social, economic and environmental consequences.” says Thomas Wahl. When storm surge and heavy precipitation co-occur, the potential for flooding in low-lying coastal areas is often amplified compared with either phenomenon in isolation. “In case of compound events the flooding risk from sea- and rainfall will double and cause even higher floods in the affected areas” emphasizes Jens Bender.

The scientists determined the likelihood of the joint occurrence of these two phenomena for the contiguous United States. In the case of New York City, the authors determine that the observed increase in compound events is attributable to storm surge weather patterns that also favour high precipitation, as opposed to weather events primarily driven by high precipitation accompanied by storm surges. They find that long-term sea-level rise is the main driver for increased flooding along the US coastline, but changes in the joint distributions of storm surge and precipitation associated with climate change and variability further increase flood potential.
If German and European coastal cities are also subject to a higher risk of those compound events needs to be investigated in further studies.

 

Reference: Wahl, T., Jain, S., Bender, J., Meyers, S. D., Luther, M. E. (2015): Increasing risk of compound flooding from storm surge and rainfall for major US cities, doi: 10.1038/nclimate2736.

Contact:

Thomas.wahl@uni-siegen.de
Jens.bender@uni-siegen.de