Odds of storm waters overflowing Manhattan seawall up 20-fold

A press release from the American Geophysical Union: Maximum water levels in New York harbor during major storms have risen by nearly two and a half feet since the mid-1800s, making the chances of water overtopping the Manhattan seawall now at least 20 times greater than they were 170 years ago, according to a new study. Whereas sea-level rise, which is occurring globally, has raised water levels along New York harbor by nearly a foot and a half since the mid-19th century, the research shows that the maximum height of the city’s “once-in-10-years” storm tide has grown additionally by almost a foot in that same period.

The newly recognized storm-tide increase means that New York is at risk of more frequent and extensive flooding than was expected due to sea-level rise alone, said Stefan Talke, an assistant professor of civil and environmental engineering at Portland State University in Portland, Ore. He is lead author of the new study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union. The research also confirms that the New York harbor storm tide produced by Hurricane Sandy was the largest since at least 1821.

Tide gauge data analyzed in the study show that a major, “10-year” storm hitting New York City today causes bigger storm tides and potentially more damage than the identical storm would have in the mid-1800s. Specifically, Talke explained, there’s a 10 percent chance today that, in any given year, a storm tide in New York harbor will reach a maximum height of nearly two meters (about six and a half feet), the so-called “10-year storm.” In the mid-19th century, however, that maximum height was about 1.7 meters (about 5.6 feet), or nearly a foot lower than it is today, according to tide gauge data going back to 1844, he noted.

“What we are finding is that the 10-year storm tide of your great-, great-grandparents is not the same as the 10-year storm tide of today,” Talke said.

... The study’s findings may indicate that “storm surges’ interaction with New York harbor has gotten larger so that in addition to sea level rise, the storm surges may have been enhanced,” said Chris Zervas, a scientist at NOAA’s Center for Operational Oceanographic Products and Services in Silver Spring, Md., who was not involved in the study. “For the latter part of the 1900s, [it shows] that the possibility of overtopping the seawall has increased quite a bit in addition” to sea-level rise, he added...

The Hugh L. Carey Tunnel (formerly known as the Brooklyn Battery Tunnel) on Oct. 30, 2012, during Hurricane Sandy, shot by Metropolitan Transportation Authority of the State of New York, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license 

High tides likely to bring more floods, UK's Environment Agency warns

The Guardian (UK): The Environment Agency has warned that Saturday afternoon high tides will bring a further risk of flooding despite an improvement in conditions.

The agency said there were four severe flood warnings in place, three on the river Severn and one on the Lower Stour at Iford in Kent. There were a further 97 flood warnings and 244 flood alerts in place. The agency has removed 175 warnings or alerts in the past 24 hours.

The Met Office has issued yellow warnings of rain in the south of England and snow in the north of England and southern parts of Scotland. Up to 3cm of rain could fall in just six hours, and there are more warnings of flooding and travel disruption.

Residents in Chiswell and Portland in Weymouth, Dorset, were evacuated ahead of high tide on Friday night, while around 100 people living in Aberystwyth, Dyfed, were advised to move to higher ground, with many taking shelter in rest centres.

The ferocious weather has left widespread damage. In Aberystwyth debris was strewn across the promenade, rail lines in north Wales were left buckled by the power of the sea and a road collapsed in Amroth, Pembrokeshire.

Police continued the search for Henry Martin, 18, who has not been seen since he left his home in Membland, Newton Ferrers, near Plymouth, Devon, to take pictures of the weather on Thursday. Air, sea and land searches were undertaken. Martin had recently started a course in film and TV production at Greenwich University in London but was back home visiting his family for Christmas...

High waves in Blackpool, shot by R lee, Wikimedia Commons via Geograph UK, under the Creative Commons Attribution-Share Alike 2.0 Generic license

High tides illustrate vulnerability of San Diego’s shoreline

ScoopSanDiego: This week, some of the year's highest tides will breach California's coastal and bay shorelines, providing a glimpse of what the state can expect as sea levels rise in the coming years. Local environmental organizations are working within a statewide initiative to have volunteers in San Diego County document this winter's highest tides - known as "King Tides." Local organizers are focused on capturing coastal images on Dec. 23 - 24, 2011, Jan. 20 - 22, 2012, and Feb. 6 - 8, 2012.

Last year, photos taken during some of the highest tides of the year documented impacts to private property, public infrastructure and wildlife habitat across the state. As a result, the California King Tides Initiative was launched in the winter of 2010/2011 by a partnership of organizations including the Tijuana River National Research Reserve, San Diego Coastkeeper, WiLDCOAST and Surfrider San Diego Chapter.

Statewide, the organizations will use the photography to help policymakers visualize projected impacts from rising sea levels and take action to protect key infrastructure as well as wetlands, beaches and public access to the coast. The Initiative can engage Californians in a conversation about the future of coastal areas, identify and catalog coastal areas that are currently vulnerable to tidal inundation and build an online resource of images that can be used by everyone to communicate about coastal hazards.

"King tides demonstrate the power of visualization and give us a rare chance to see how higher sea levels and increased storm intensity could change our shoreline and impact our resources," says Kristen Goodrich, Coastal Training Program Coordinator at the Tijuana River National Estuarine Research Reserve. "One common sense approach to adapting to climate change impacts is to restore and protect wetlands, which function like natural sponges, buffering against rising sea levels, higher tides and increased storm and wave activity."...

High tide at San Diego's Ocean Beach Pier in 2002, during an El Nino, shot by Jon Sullivan, who has generously released this image into the public domain

Higher tides affecting the US east coast, especially mid-Atlantic

Scott Harper in the Virginian-Pilot (Hampton Roads, Virginia): Scientists are closely watching unusually high tides along the entire East Coast, especially in mid-Atlantic states including Virginia, where average daily levels are running between 6 inches and 2 feet above predicted norms.

One veteran researcher at the Virginia Institute of Marine Science, John Boon, said he suspects the trend could be the beginning of a decade-long phenomenon of high water caused by an El Niño-like effect in the Atlantic. “It’s possible we’re entering a new cycle,” he said this week.

Boon, a professor emeritus of marine science who has studied tides most of his career, described how Atlantic wind patterns and currents can subtly shift, often without explanation. The shift, in turn, pushes more water onto East Coast beaches, marshes and coastline through higher tides.

...The extreme tides, he and other scientists said, have occurred before and can last, on and off, for years at a time before suddenly changing back to normal. “There’s no scientific debate that these anomalous cycles happen,” Boon said. “It’s what causes them that’s debated.”

…Similarly on the Atlantic, quirky shifts in atmospheric pressure and winds, known as the North Atlantic Oscillation, contribute to weather variability – and might be at play now, said Larry Atkinson, an oceanographer at Old Dominion University in Norfolk. Atkinson said that what Hampton Roads is experiencing now will likely become the norm in 30 or 40 years due to sea level rise associated with the slow warming of ocean temperatures….

A statue of Neptune in Virginia Beach, Virginia, shot by Dmc313, who has generously released the image into the public domain