Sea Level Rise Driving Increase in Tidal Flooding

Flooding caused by high tides is often called “nuisance flooding”.  As sea levels rise, however, tidal floods are expected to become a more serious problem.

According to a report released this week by the Union of Concerned Scientists, coastal communities along this country’s East and Gulf coasts should expect to see a dramatic increase in tidal flooding over the next 30 years. Analyzing data from 52 tide gauges from Maine to Texas, researchers looked at how often communities flood now as compared to the past. They found that some areas have seen a fourfold increase in the annual number of flood days since 1970. Using a mid-range scenario of future sea level rise from the 2014 National Climate Assessment, the scientists forecast that, “more than half of the 52 communities can expect to average more than two dozen tidal floods per year by 2030.” Some areas, especially in the mid-Atlantic, can expect a tripling in the frequency of tidal flood events.

The report also states, “This flooding will define how and where people in affected areas live, work, and otherwise go about their daily lives.” Recognizing the need to adapt, the report offers “sensible steps for building resilient coastal communities.” These include upgrading infrastructure and developing both short and long-term plans to deal with sea level rise.

A tide that causes a minor flood today is a nuisance (white arrow). In the future, higher sea levels will allow high tides to push water deeper into coastal communities, affecting more homes, businesses, and infrastructure. Extensive moderate flooding—now usually associated with storms and high winds—is expected to become more common, simply from high tides.  Credit: UCS

Flooding – now usually associated with storms – is expected to become more common, simply from high tides.  Credit: UCS

Record Rainfall Floods Long Island

Record rainfall swamped New York’s Long Island on Wednesday morning. Flash floods prompted evacuations, submerged cars on major roadways, and even uprooted trees. Local officials have also reported one weather-related death.

One of the hardest hit areas was Islip in Suffolk County, where 13.27 inches of rain fell in less than 24 hours. That is more than the town would normally get for an entire summer season and is nearly double its previous daily record of 6.7 inches set in August 1990. The storm also shattered the record for 24-hour rainfall in New York State. The previous record was 11.6 inches, which was measured in Tannersville, NY during Tropical Storm Irene in August 2011.

The intensity of this rain event, according to the NWS, was caused by a few factors. First, several different weather systems came together over Long Island and were fed by moisture from the Atlantic Ocean. Then, the storm essentially stalled in place for hours.

While Suffolk County bore the brunt of the rain, flash flooding also caused problems in nearby sections of New Jersey and Connecticut. Here in New York City, we were mostly unscathed. JFK airport (in Queens) reported 3.2 inches of rain, but less than an inch was measured in Central Park.

Flood waters strand cars on Sunrise Highway in Valley Stream on Long Island, NY.  Credit: wpix11

Flood waters strand cars on Sunrise Highway in Valley Stream on Long Island, NY.                 Image Credit: pix11

A Day of Drenching Rain in NYC

April is famous for its showers, but yesterday’s precipitation was extreme. Torrential downpours brought New York City more than a month’s worth of rain in a single day.

According to the NWS, 4.97 inches of rain was measured in Central Park. Not only is that a new daily record for the date, it was the 10th rainiest day ever recorded in NYC. On average, we normally get 4.50 inches of rain for the entire month of April.

Up until yesterday, the city’s rainfall total was running below average for the month. So, while the rain was beneficial for the area, the rate at which it came down and its extended duration caused a number of localized flooding problems.

Scientists say the frequency of extreme rain events like this one will increase as global temperatures rise and our climate changes.

Super-Storm Sandy: One Year Later

One year ago today, Super-storm Sandy slammed the New York City tri-state area.  Despite being downgraded from hurricane status just prior to landfall, Sandy was the second costliest natural disaster in U.S. history.

Coming ashore with tropical storm-force winds at high tide, Sandy caused a record 13.88-foot storm surge.  It flooded many low-lying areas, including parts of the NYC subway system.  Damaging or destroying more than 650,000 homes, the massive storm displaced thousands of people for months.  According to NOAA, Sandy claimed the lives of 159 people and caused approximately $65 billion in property damage.  The storm also knocked out power to 8.5 million people for multiple days – including most of Manhattan south of 34th Street.

Sandy’s flooding storm surge also highlighted the dangers posed by rising sea levels.  In the wake of the storm, many government agencies – at all levels – began re-evaluating their strategies for dealing with future natural disasters.  The National Hurricane Center changed its policy for issuing warnings on post-tropical storms and is developing a new storm surge warming system. New York City’s Office of Emergency Management re-drew its hurricane evacuation zones. And, the National Flood Insurance Program, operated by FEMA, began implementing new policy rates for homes and businesses in flood prone areas.

While the arduous process of rebuilding is ongoing, progress has been made across the region.  Recovery levels vary by location.

A Cyclone and Typhoon Batter India and Japan

Hurricanes can develop all over the world, but they are referred to by different names – cyclones or typhoons – in different regions. This past week, two separate storms slammed India and Japan.

In India, Cyclone Phailin barreled across the Bay of Bengal and made landfall in the state of Orissa on Saturday.  Packing winds of 131-mph, it was the equivalent of a category-4 hurricane. Local officials say the storm’s flooding rains and strong winds destroyed tens of thousands of homes and claimed the lives of at least twenty-seven people.  The government’s pre-storm evacuation of nearly one million people, however, is credited with keeping the number of fatalities from being much higher. Sadly, a cyclone that hit the same area fourteen years ago left approximately ten thousand people dead.

On Wednesday, Typhoon Wipha rumbled along the coast of Japan near Tokyo. With sustained winds of 78-mph, it was the equivalent of a category-1 hurricane.  This storm’s torrential rain caused rivers to overflow and triggered deadly mudslides. One of the hardest hit areas was Izu Oshima, an island about seventy-five miles south of the capital, where a record 32.44 inches of rain fell in one twenty-four period.  Officials say this powerful storm destroyed more than three hundred homes and caused the deaths of at least seventeen people. According to the Japan Meteorological Agency, Wipha was the eighth typhoon of 2013.

Back in the United States, the Atlantic hurricane season remains fairly quiet.

Two Tropical Storms Cause Flood Disaster in Mexico

The hurricane season in the U.S. has been fairly slow this year – at least so far.  Mexico, our neighbor to the south, however, has not been so lucky.

Hit from both sides, Mexico was slammed by two separate tropical storms this week.   Manuel moved in from the Pacific and Ingrid came ashore from the Gulf.  Both storms brought torrential rain that caused widespread flooding, landslides, and power outages.  Impacting millions of people across the country, this one-two punch of extreme weather claimed the lives of at least one hundred people and displaced thousands more. 

One of the hardest hit areas was Acapulco on the west coast, where 7.43 inches of rain is reported to have fallen in one twenty-four hour period.  The flooding was so severe in this popular resort town that it turned roads into raging muddy rivers and carried crocodiles into the city.  With the only highway out of town destroyed in a landslide and the airport submerged in waist deep water,  locals along with nearly forty-thousand tourists have been stranded there for days.  

According to the Mexican National Weather Service, the last time Mexico was hit by two tropical storms within a span of twenty-four hours was back in 1958.

Colorado Flood Disaster

Relentless rain unleashed catastrophic flooding across Colorado’s Front Range this past week. While flash floods are not uncommon in the area, officials say the magnitude and duration of this event makes it one of the worst disasters in the state’s history.

According to meteorologists, the cause of this widespread and destructive flooding was a stalled low-pressure system that funneled moisture into the region from both the Gulf of Mexico and Pacific Ocean.  Forced upward by the local topography – the Rocky Mountains – this moist air condensed into rain clouds. Without upper level winds to move the system along, rain just kept falling locally. In Boulder County, one of the hardest hit areas, 18 inches of rain fell in one week.  They normally receive 20 inches for the entire year.

Impacting seventeen counties across the state, raging floodwaters turned roads into rivers obliterating thousands of homes and claiming the lives of at least eight people.  Local officials say hundreds of miles of roadways and dozens of bridges were damaged or destroyed.  This has left anyone living in small mountain towns stranded and cut off from basic services like power, communications, and clean water.

This devastating deluge follows a summer marked by drought and wildfires across the state.

Floods Nurture Congaree National Park

Floods are often thought of as disasters, especially when people and property are harmed. In nature, however, some ecosystems thrive on periodic flooding. While traveling in South Carolina last week, I had the opportunity to visit one such place – Congaree National Park.

Situated in the floodplain of the meandering Congaree and Wateree Rivers, the park protects the largest expanse of old growth bottomland hardwood trees still standing in the southeastern United States.  It is home to a dazzling array of biodiversity, including a number of champion trees – tress that hold the size record for their species.  These include a bald cypress with a circumference of twenty-seven feet and a loblolly pine standing one hundred seventy feet tall.  These trees would not be able to flourish without the moisture and nutrient–laden sediments that flood waters bring to the forest floor.

This floodplain forest is typically inundated by water several times a year. During my visit, the park was about 90% flooded as a result of recent heavy rainfall on top of an already wet spring.  It was an impressive sight.

The elevated boardwalk trail in Congaree NP disappears into high flood waters.

The elevated boardwalk trail in Congaree NP disappears into high flood waters.

Image Credit: The Weather Gamut

Sandy Highlights the Dangers of Rising Sea Levels

Six months ago today, Super-storm Sandy devastated a large section of the northeastern United States.  The flooding caused by its record storm surge was a heart-wrenching example of the dangers posed by rising sea levels.

Storm surge is the rise in sea height that occurs during an intense storm like a hurricane or nor’easter. Its baseline is local sea level. So, as sea levels rise, storm surges are able to reach further inland.  This is a serious problem for coastal communities around the world.

According to climate scientists, the average global sea level has risen about eight inches since 1880.  This may not sound like a lot, but it is a significant amount when you consider it is spread out across all of the world’s oceans.  That said, sea levels are not rising evenly across the planet.  Recent studies have found that certain areas, such as the East Coast of the US, are experiencing faster rates of sea level rise than others.  New York Harbor, for example, has seen its water level increase by more than a foot in the past century.

Sea level rise has two main drivers. They are thermal expansion – a process in which water expands as it warms – and the melting of massive amounts of land based ice, such as glaciers and ice sheets.  Both are the result of rising global temperatures.

In the future, sea levels are expected to continue rising as our atmosphere warms. Estimates of how much vary from four inches to two feet above current levels by 2050. This wide range reflects uncertainty in the amount of future greenhouse gas emissions, subsequent warming, and rate of ice melt.  What is certain, however, is that the frequency and magnitude of storm surge flooding will increase as sea levels rise.

Mapping Sandy’s Floodwaters in NYC

Forecasters predicted Sandy would be a serious storm – and it was.  Its storm surge, however, was higher and even more catastrophic than had been anticipated.

The New York Times, earlier this week, published an interactive map of the flooding caused by the super-storm in New York City.  It is an incredibly detailed visualization of how high the floodwaters actually reached in different parts of the city.