seawalls

Natural solutions for disappearing islands

June 12, 2025 By EarthWise Leave a Comment

Atoll islands are made from sediment produced by corals, clams, snails, and varieties of algae that secrete carbonate. Under the right conditions, over time, fragments of coral skeletons, shells, and other sediments made by marine life are piled up by waves. Eventually, islands are formed – some large and some small. Atoll islands are home to a diversity of human cultures and are important refuges for a quarter of the world’s seabirds as well as numerous nesting sea turtles and tropical plants.

Rising sea levels – the rate of which has more than doubled over the past 30 years – are a mounting challenge for atoll islands. And by the end of this century, sea level is projected to rise between 11 and 40 inches, depending on the world’s actions with regard to greenhouse gas emissions.

The ability of atoll islands to persist depends on the health of their ecosystems and the extent to which their natural processes have been disrupted by human activity. To protect the most vulnerable islands, some researchers now propose using nature-based solutions – like restoring and protecting coral reefs and native forests.

Reclaiming seabird habitat can help reefs persist and restore the resilience of atoll islands. Seabird guano washes off islands and into reefs, providing nutrients that boost coral growth and fish populations.

Nature-based solutions cannot help the most urbanized atoll islands. These islands have already irreversibly lost their natural adaptive capacity. For those places, engineered approaches such as concrete seawalls are needed.

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How Natural Solutions Can Help Islands Survive Sea Level Rise

Photo, posted July 3, 2014, courtesy of Roderick Eime / MG Media via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Protecting New York City From Flooding | Earth Wise

April 21, 2023 By EarthWise Leave a Comment

Hurricane Sandy flooded Lower Manhattan in October 2012, closing Wall Street, blacking out power for 250,000 people, and killing 44 New Yorkers. Within a year, plans were in motion to build berms, floodwalls, and water gates along the city’s Lower East Side in a $770 million first phase of an overall plan to defend New York City from future floodwaters.

Plans got more and more complicated, and the price tag reached $1.45 billion before the existing plan was scrapped by former Mayor Bill de Blasio’s administration in 2018 without involving the community groups that were instrumental in creating the original plan. After years of lawsuits and court actions, the revised East Side Coastal Resiliency Project is finally proceeding, now at a price tag approaching $3 billion. The project will include 18 moveable floodgates and will protect 110,000 New Yorkers, including 28,000 low-income public-housing residents and is expected to be completed in 2026.

The original larger overall plan was halted in 2020 after former President Trump mocked it and claimed that it would cost $200 billion. The current plan, created by the U.S. Army Corps of Engineers and known as the 3B alternative, calls for a combination of deployable flood barriers, floodwalls, seawalls, and elevated promenades wrapping around the lower part of Manhattan. The cost of the project is estimated to be $61 billion.

In the meantime, over 10 years after Sandy, a similar storm would have almost the same effect today as Sandy had back then.

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New York City Begins Its Climate Change Reckoning on the Lower East Side, the Hard Way

Photo, posted January 19, 2013 courtesy of Andres Alvarado via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

The Rising Threat Of Rising Seas | Earth Wise

February 3, 2020 By EarthWise Leave a Comment

Global sea level rose by about 6 inches during the 20th century. It is currently rising more than twice as fast and accelerating. The rate of rise was 2.5 times faster from 2006 to 2016 than it was for nearly all of the 20th century.

Sea level rise occurs when glaciers and ice sheets lose mass. Much of that meltwater comes from Greenland and Antarctica. But levels also rise because, as water warms, it expands. Added to that are the effects of human activities such as groundwater depletion and a geological phenomenon called isostatic adjustment that is going on in parts of the East Coast where the land is actually sinking.

In Atlantic Canada, sea level rise is outpacing the global average and has already led to boardwalks swamped by swelling tides, drowned forests, submerged wharfs, and threatened historic shoreline buildings.

Recent research suggests that globally, land now occupied by 300 million people could be affected by floods at least once a year by 2050 unless carbon emissions are significantly reduced, and coastal defenses strengthened. (This new figure is more than three times higher than earlier estimates).

Researchers at Dalhousie University in Nova Scotia are studying nature-based strategies for mitigating the effects of the rising seas. These include conserving or restoring coastal ecosystems like dunes, wetlands, and reefs which could provide protection at a lower cost than building seawalls and other man-made obstacles. Wetlands, for example, can reduce the force of waves and act as obstacles to storm surges, while also trapping sediment and stemming erosion. Wetlands also serve as important carbon stores, but it is estimated that roughly half of the world’s coastal wetlands have been lost over the past 100 years to human activity and extreme weather events.

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The Looming Threat of Rising Sea Levels – And What We Can Do About it

Photo, posted February 14, 2015, courtesy of Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Should New York Build A Storm Surge Barrier?

December 6, 2019 By EarthWise Leave a Comment

In 2012, Superstorm Sandy’s storm surge combined with a high tide and buried lower Manhattan under 13 feet of water. Across all five boroughs, subways, highways, and parking garages flooded and homes and businesses were destroyed. Sandy caused nearly $20 billion in damages in New York City alone and more than 50 people died.

Ever since that disaster took place, there have been discussions about building storm surge barriers to protect the city from future storms. Columbia University’s Sabin Center recently hosted an event to discuss the feasibility of building such barriers.

A study by the U.S. Army Corps of Engineers called the NY and NJ Harbor and Tributaries Focus Area Feasibility Study (HATS, for short) evaluates five options for coastal protection, which range in scope and price.

The most extensive option would involve constructing six miles of storm surge gates along with 26 miles of floodwalls, levees, and buried seawalls. This option would cost $62 billion but could theoretically save $131 billion in damages and protect 95% of the study area.

The study also considers the side effects of building storm surge barriers. These include environmental impacts such as effects on fish and wildlife, water quality, noise and vibrations, and changes in water flow. While these effects can be quite serious and there is opposition from many quarters related to environmental impacts, others point out that there is really no other credible defense against storm surge. The debate over whether or not to build storm surge barriers could easily last for many more years.

In the bigger picture, storm surge barriers do nothing to protect against rain-driven flooding, sea level rise, and tidal floods which continue to increase.

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Should New York Build a Storm Surge Barrier?

Photo, posted October 30, 2012, courtesy of Pamela Andrade via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.