Not Just Sea Level Rise: Northeast Faces Flooding From The Skies

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"Not Just Sea Level Rise: Northeast Faces Flooding From The Skies"

Flash flooding in Waitsfield, Vermont during Hurricane Irene.

Flash flooding in Waitsfield, Vermont during Hurricane Irene.

CREDIT: A.P. Images

The nation’s capital and financial center, not to mention other major metropolitan areas in the Northeast, are going to get soggy. And not just because of dramatic sea level rise and storm surge. The third National Climate Assessment, released Tuesday, stresses that the onslaught of water will come from the skies as well as the oceans.

In the aftermath of Superstorm Sandy, which slammed into the East Coast in October 2012, causing up to $80 billion in damage, most people in the Northeast quickly became familiar with the threat posed by sea level rise. Since 1900, the East Coast has seen about one foot of sea level rise — four inches more than the global average. And the area could see anywhere from another foot to four additional feet by the end of the century.

But the National Climate Assessment makes it clear that future flooding in the region won’t be limited to coastal areas. Precipitation is not only increasing in the area, but the incidence of extreme precipitation events, which often spark flash flooding, is on the rise as well.

Robert Bazouzi is no stranger to flooding. During Superstorm Sandy he used an inflatable air mattress to raft down his street in Hoboken, New Jersey to help get supplies for his family and the other people stranded in the apartment building by waist-high flood waters. His small hair salon, which he had just opened days before Sandy hit, was completely destroyed. But he rebuilt, and in compliance to LEED Silver Standards for energy efficiency.

“It was more expensive, and took me longer to get back on my feet, but I had to do something to help,” he said.

And Bazouzi is well aware of the fact that it doesn’t take a superstorm to flood his city. Just a few hours of heavy rain leave streets in low-lying areas of town impassable — an occurrence likely to happen with greater frequency as climate change accelerates.

“Hearing that we will have even more flash floods around here makes me want to move,” he said. “But we can’t all just pick up and go.”

Precipitation in the Northeast has increased by about five inches since 1895, or to look at it another way, the area has experienced about a 10 percent increase in precipitation every decade. And those extra inches haven’t been nicely scattered throughout the years; between 1958 and 2010, the Northeast saw more than a 70 percent increase in the amount of precipitation falling in very heavy rainfall events — the heaviest one percent of events, in fact.

While almost all of the nation has experienced this trend to some degree, the Northeast has experienced a greater recent increase in extreme precipitation than any other region of the United States. Only the Midwest even comes close, with a 37 percent increase in extreme precipitation events.

NE.Precip

CREDIT: National Climate Assessment 2014

According to Rob Moore, a water and climate expert at the Natural Resources Defense Council, 25 percent of flood damages in the country stem from heavy rainfall overwhelming stormwater systems, rather than flooding we normally associate with rivers rising over their banks.

While the report stresses that no single extreme weather event can be definitively linked to climate change, the authors call events like Hurricane Irene in 2011,”teachable moments” that revealed the region’s vulnerability to the kinds of extreme precipitation events that are likely to occur with increasing frequency in the years to come.

In preparation for Irene, 2.3 million coastal residents in Delaware, New Jersey and New York were told to evacuate. In the end, however, it was the inland flooding caused by heavy rainfall, rather than coastal flooding due to storm surge, that took the biggest toll. People who fled away from the coasts often ran straight into the worst of the flooding. In Vermont, which was perhaps hardest hit by unrelenting rain, over 500 miles of roads and 200 bridges were damaged and 17 municipal wastewater treatment plants were breached. Rebuilding costs reached a staggering $175 to $250 million.

As if on cue, just a week before the report was released, a slow-moving storm system that brought deadly tornadoes to the Plains and the Deep South dumped weeks worth of rain on the Northeast, causing widespread flash flooding.

New York City was slammed with nearly six inches of rain in 24 hours, triggering a mudslide that covered three of four Metro-North commuter rail tracks in Yonkers and left several streets in Queens more than two feet deep in water. Washington, D.C. tried to cope with a month’s worth of rain in a single day and in Maryland, hundreds of people had to be evacuated when officials opened the floodgates at a dam in Laurel, letting floodwaters gush onto major roads.

Ironically, the region expected to see the greatest increase in extreme precipitation events, is also the region with some of the most decrepit infrastructure for handling water. Almost every major city in the Northeast region, including New York City, Boston and Philadelphia, has combined sewer systems — so the same pipes that handle wastewater also have to cope with stormwater — something they are increasingly unable to do as downpours become more intense.

When these systems back up, it not only exacerbates the flash flooding problem, it also means people can be exposed to dangerous pathogens in sewage water. The National Climate Assessment notes that studies in Connecticut have found that the risk for contracting a stomach illness while swimming significantly increased after just one inch of rain.

“Water quality is one of the consequences of climate change that very few people think about,” said Moore of NRDC. “It’s more water quantity that we think about, too much or too little, in relation to the climate. But these heavy downpours often wash sewage into water bodies and dump dangerously high levels of nutrients from fields into our lakes and streams, which kill wildlife.”

Moore says that while cities figure out how to pay for upgrading their sewer systems and work on expanding green infrastructure, like permeable pavement, rain gardens and green roofs, there’s something very simple that Northeast residents can do to help protect against flash flooding.

“Use less water,” said Moore. “That seems odd when we’re talking about an area where the problem may be too much water, but if households use less water, that’s less water going into the combined sewer systems and it reduces the chance of overflow when we do get hit with a big storm.”

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