Increased Risk of Compound Urban Flooding May Sink Cities

The paper describing their research on the causes of compound flooding in urban areas of the U.S will appear in Nature Climate Change (Vol. 5, August, 2015) and is now available online.

Researchers also analyzed data specific to New York City and said the extreme flooding during Hurricane Sandy in 2012 was the result of an extreme storm surge, but that rainfall during the storm was “small in the historical context for such an event.” When all three happen together, it would be expecting the worst, especially for the low-lying densely populated and heavily developed regions in the U.S. A “Storm surge’ is an event caused by weather events which sees the relationship between the abnormal rise of water during a storm and the heavy precipitation on land, and both of these factors were mainly studied”. However other researchers not related to the study such as Philip Orton, a physical oceanographer at the Stevens Institute of Technology, have identified global warming as the reason behind heavy rainfall and have credited rising sea levels with the increase in coastal floods. In fact, if we don’t act fast to reverse the trend studies show that the odds of New York getting flooded by a combination of heavy rain and surging ocean tides has more than doubled in the last eight decades.

The largest cities in the United States are at much bigger risk of catastrophic flooding than previously thought. Consequently, they looked more closely at selected regions along the Atlantic coast.

A new study by scientists of the University of South Florida’s College of Marine Science dwells on this phenomenon known as “compound flooding” and has raised the alarm and triggered awareness on the impending risk and devastation that is to come, pointing in particular to communities along the Atlantic and Gulf coasts.

However, he also notes that such projections “may result in an underestimation of the flood risk”.

Overall, they found that the number of compound flooding events has been steadily increasing over the past century along many stretches of coastline. Wahl and his colleagues said there needs to be more research at local levels to determine risks and effects. “That research will require complex, integrated modeling experiments that investigate surface and drainage flows and include storm surge, rainfall and river discharge”. A storm surge could do that alone.