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From NOAA 12-19-14
Sea level rise has given high tide flooding of our coastal areas a significant boost. It is expected that nuisance tides will increase dramatically in the next 15-30 years causing significant damage to urban infrastructure and making some neighborhoods uninhabitable. NOAA Tide level gauges from Portland Maine to Freeport Texas, show that daily nuisance floods have increased dramatically and are rapidly accelerating.
NOAA scientists Sweet and Joseph Park established a frequency-based benchmark for what they call “tipping points,” when so-called nuisance flooding, defined by NOAA’s National Weather Service as between one to two feet above local high tide, occurs more than 30 or more times a year.
Decades of tipping point crossings.
Based on that standard, the NOAA team found that these tipping points will be met or exceeded by 2050 at most of the U.S. coastal areas studied, regardless of sea level rise likely to occur this century. In their study, Sweet and Park used a 1½ to 4 foot set of recent projections for global sea level rise by year 2100 similar to the rise projections of the Intergovernmental Panel for Climate Change, but also accounting for local factors such as the settlement of land, known as subsidence.
These regional tipping points will be surpassed in the coming decades in areas with more frequent storms, the report said. These tipping points will be also be exceeded in areas where local sea levels rise more than the global projection of one and half to four feet. This also includes coastal areas like Louisiana where subsidence, which is not a result of by climate change, is causing land to sink below sea level.
NOAA tide gauges show the annual rate of daily floods reaching these levels has drastically increased – often accelerating – and are now five to ten times more likely today than they were 50 years ago.
“Coastal communities are beginning to experience sunny-day nuisance or urban flooding, much more so than in decades past,” said Sweet. “This is due to sea level rise. Unfortunately, once impacts are noticed, they will become commonplace rather quickly. We find that in 30 to 40 years, even modest projections of global sea level rise -- 1½ feet by the year 2100 -- will increase instances of daily high tide flooding to a point requiring an active, and potentially costly response, and by the end of this century, our projections show that there will be near-daily nuisance flooding in most of the locations that we reviewed.“
The importance of this research is that it draws attention to the largely neglected part of the frequency of these events. This frequency distribution includes a hazard level referred to as ‘nuisance’: occasionally costly to clean up, but never catastrophic or perhaps newsworthy,” said Earth’s Future editor Michael Ellis in accepting the paper for the online journal.
Ellis also observed that “the authors use observational data to drive home the important point that nuisance floods (from inundating seas) will cross a tipping point over the next several decades and significantly earlier than the 2100 date that is generally regarded as a target date for damaging levels of sea-level. The paper also raises the interesting question of what frequency of ‘nuisance’ corresponds to a perception of ‘this is no longer a nuisance but a serious hazard due to its rapidly growing and cumulative impacts’."
The scientists base the projections on NOAA tidal stations where there is a 50-year or greater continuous record. The study does not include the Miami area, as the NOAA tide stations in the area were destroyed by Hurricane Andrew in 1992 and a continuous 50-year data set for the area does not exist.
Based on that criteria, the NOAA team is projecting that Boston; New York City; Philadelphia; Baltimore; Washington, D.C.; Norfolk, Virginia; and Wilmington, North Carolina; all along the Mid-Atlantic coast, will soon make, or are already being forced to make, decisions on how to mitigate these nuisance floods earlier than planned. In the Gulf, NOAA forecasts earlier than anticipated floods for Galveston Bay and Port Isabel, Texas. Along the Pacific coast the earlier impacts will be most visible in the San Diego/La Jolla and San Francisco Bay areas.
Communities that rarely if ever experience this type of tidal flooding will be forced to adapt to a new normal of regular flooding, and in some areas a new normal of daily floods. NOAA is encouraging Coastal cities to plan for abandoning some areas and retreating inland. Mitigation efforts such as fortification and green infrastructure such as dunes and wetlands as well as gray infrastructure such as sea walls, pumping stations and storm water systems are also advised and that plans should be in place as soon as possible.
The Union of Concerned Scientists notes:
By 2045, many coastal communities are expected to see roughly one foot of sea level rise. The resulting increases in tidal flooding will be substantial and nearly universal in the 52 communities analyzed.
One-third of the 52 locations would face tidal flooding more than 180 times per year. Nine locations, including Atlantic City and Cape May, New Jersey could see tidal flooding 240 times or more per year.
A growing proportion of these floods would be extensive, and as floods reach farther into communities, they would also last longer. Flood-prone areas in five of the mid-Atlantic communities studied could be inundated more than 10 percent of the time.
As the reach of the tides expands, communities now largely unfamiliar with tidal flood conditions will be forced to grapple with chronic flooding -- a new normal. Many of the studied locations that today see fewer than five tidal floods per year could see a 10-fold increase in the number of floods annually by 2045.
Coastal communities must act with urgency to prepare for this rising threat — and there are many things we can do to help ensure enduring coastal communities.
Municipalities, with state and federal help, should prioritize and incentivize flood-proofing of homes, neighborhoods, and key infrastructure; curtail development in areas subject to tidal flooding; consider the risks and benefits of adaptation measures such as sea walls and natural buffers; and develop long-term plans based on the best available science.
The costs and challenges, however, are too great for municipalities to shoulder alone. A coordinated, well-funded federal response is also needed and should include both substantial investments in coastal resilience building, as well as action to deeply and swiftly reduce global warming pollution. This latter action may ultimately be the only reliable way to protect coastal communities over the long term – by slowing the pace of future sea level rise.
There is a hard truth about adaptation, however. It has fundamental limits — whether physical, economic, or social — and it can only fend off the impacts of sea level rise to a point.
As sea level rises higher, even our best protection efforts will not suffice in some areas in the face of rising tides, waves, and storm surges.
Honolulu . (CREDIT: Photo by D. Oda)
Annapolis
Credit: Amy McGovern/flickr
Boston
Credit: tbha.org
Miami
Credit: Grist
San Francisco
Credit: Sergio Ruiz/Flickr
Manhattan
Credit: Brian Kahn
Tick, tick, tick, tick