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New Study Forecasts Dramatic Beach Erosion Along U.S. Coastline

by Stefano Valentino

May 2, 2020 | Environment

PHOTO CREDIT: Edel Rodriguez

In the time of the coronavirus, various U.S. authorities have tried to mitigate the contagion by belatedly and unevenly restricting access to beaches. Yet in the not-so-distant future, nature will accomplish what government could not, as many of these sandy areas will have been slowly wiped out by coastal erosion due to sea level rise.

In just 80 years from now, the length of a human lifetime, almost half of the beaches along the U.S. coast, and around the globe, will have approached the point of extinction from climate-driven coastal flooding and human interference. This dire prediction emerges from an authoritative new study by the Joint Research Center of the European Commission, or JRC, published in the peer-reviewed Nature Climate Change, a monthly journal dedicated to publishing the most significant and cutting-edge research on the character, underlying causes, and impacts of global climate change.

Coastal sand erosion will inflict a heavy toll on areas with a concentration of urbanization and tourism. As beaches retreat, these regions will have less of a buffer zone that now both protects them from the ravages of the oceans and provides for recreational activities. As a result, a significant proportion of coastal populations, existing residential and commercial assets, and public infrastructure will be at risk of inundation. Related revenues and taxes will decrease, and costs for future shore protection will skyrocket.

Dreams of waterfront lifestyles, holidays in tropical resorts, and plans to move to the seaside—all will likely end up relegated to old family picture albums for incoming generations of Americans.

Animal life cycles will be impacted, as beach erosion reduces the nesting areas available for birds, sea turtles, and other species populating coastal habitats.

Every lost yard of sand erosion in turn erodes public and private capital. Many of the world’s most famous beaches, mostly along densely developed shorelines, are already ecologically dead and dependent for their survival on human interventions. Public administrations have been investing in countermeasures that may prove increasingly expensive, if not socially controversial and economically unsustainable.

According to the JRC researchers, just 30 years from now, erosion will have dramatically thinned an estimated 2,451.6 miles (36.06 percent) of sandy coastline in the United States and 22,429 miles (13.6 percent) around the world. This pattern will progress further during the second half of the century, washing away projected totals of 2,451.6 miles (36.06 percent) and 59,068 miles (25.7 percent) of shorelines in the United States and the world, respectively.

Alarmingly, these predictions are far from the most catastrophic estimates. Indeed, they rely on a forecast of greened global economies and a curbing of global warming (which frankly seems optimistic given the Trump administration’s dismissal of climate change). In this more hopeful scenario, based on reduced ice-cap melt and lower thermal expansion of water, oceans will rise by only 19.7 inches during the 21st century.

However, if we continue to release carbon emissions at current rates, the International Panel on Climate Change warns that sea level rise will be 31.5 inches. In this scenario, a total of 3,436 miles (55.5 percent) of U.S. beaches will go underwater.

Globally, the average shoreline retreat will be 94 yards (the low-carbon scenario) or 140 yards (the high-carbon scenario). Actual erosion will vary from location to location. Flatter or wilder coastlines will be more affected than those where waterfronts are steeper or artificially maintained as part of coastal development.

“Erosive trends increase proportionally to greenhouse gases,” observed Michalis Vousdoukas, an oceanographer at the JRC and lead author of the study. “Moderate emissions mitigation could prevent 17 percent of the shoreline retreat in 2050 and 40 percent in 2100, thus preserving on average 46 yards of sand between land and sea.”

Interactive map of U.S. coastal erosion projections:

source: Joint Research Centre of the European Commission

In the worst climate scenario, the United States is expected to rank sixth in the international tabulation of coastal erosion, led by Australia (9,227 miles), Canada (8,963), Chile (4,138), Mexico (3,410), and China (3,380).

“We calculated the total miles of the submerged shoreline by taking into account only those locations where water will travel inland by more than 109.4 yards, assuming that there are no physical limits to potential retreat,” Vousdoukas said. “However, the chosen 109.4 yards threshold is conservative, since most beaches have widths below 54.7 yards, especially near human settlements and in small islands, such as [those in] the Caribbean and the Mediterranean. If we consider all locations affected by a 54.7 yards retreat, then the total miles of submerged shoreline will likely be a much higher number.”

Large beaches will narrow by a range of 109.4 yards to over 218.7 yards on Atlantic and Pacific seaboards and the Australian side of the Indian ocean, wiping out over 60 percent of sand in a number of developing countries that are economically fragile and heavily dependent on coastal tourism.

How development impedes beach replenishment

Historically in the United States, the east coast has been the most affected by sea level rise, with 86 percent of the beaches already experiencing a high level of erosion. However, the last decade has seen a dramatic shift also in the west coast, where the waters have grown much warmer, and the sea is now rising faster there than elsewhere in the world.

“Sea level rise is exacerbating the problem of shoreline construction and catchment barriers (such as buildings, roads, dams) that have depleted the natural supply of replenishing sediment for sandy beaches,” Vousdoukas said.

Sediment flows down from mountain streams and waterways and stops only temporarily on any specific seashore. This natural supply takes years to build up and is crucial in feeding the beaches. Any human disruption to sand migration could reveal itself elsewhere on the given coastline. In some regions, however, marine erosion is counteracted by land rise, which is an upward extension of the coastline (the land abutting the Baltic Sea, for example, is slowly rising).

Sediments may also be carried by rivers, either naturally, as in the Amazon, or driven by artificial activities such as those in the Chinese deltas, where residues accumulate from upstream industrial sites.

Scientists at the JRC projected future man-made and natural changes, assuming that they will follow the same trends observed over the last 30 years. Both variables, amplifying or counteracting sea level rise, will contribute to the actual variation of the seashore width. Despite the general pattern, a few shorelines are thus expanding, because sediments outweigh sea level rise. However, according to the projections in the new JRC study, sea level rise will prevail over sediment collection on the shorelines in the United States by a considerable margin.

Man-made obstruction to the natural replenishment of beaches is a long-term process, as much as sea level rise, and has been documented in several locations on both U.S. coasts. For instance, San Francisco’s famous seafront neighborhood Pacifica has eroded so quickly in part because of all the sand dredging farther up the coast in the Bay. Trendy spots around Los Angeles have shared the same fate. Many Malibu beaches lost significant amounts of sand after the Pacific Coast Highway was created. In Santa Monica, fresh sediment rarely reaches the coast because the creeks were dammed and the L.A. River was turned into a concrete channel.

Unintended consequences

The same goes for South Carolina. In Charleston, three-mile-long rocky jetties were built in the 1800s to create a wider and deeper channel that would provide access to the harbor for increasingly large commercial ships. The construction of the jetties has blocked the flow of sediment over time. As a result, many beaches along the Charleston coast have eroded severely, shaking the local multibillion-dollar tourism industry.

“A third, more minor, driver of erosion that we assessed to make our predictions is the intensification of storms,” Vousdoukas observed. “Associated with climate change, wave surges will further erode the most vulnerable beaches.”

The east coast of the United States, in particular, is exposed to an increasing risk of catastrophic storms. In 2016 and 2017, Hurricanes Matthew and Irma saddled Florida with millions of dollars of spending to replenish vanished beaches. In 2012 and 2018, North Carolina had to pay the bills incurred by Hurricanes Sandy and Florence to avoid losing summer tourism revenues.

By the end of the century, up to 63 percent of the earth’s low-lying coastal regions, which host one beach out of three, will be menaced. In these areas, both population density and development tend to be higher than in the hinterlands.

“Seaward human expansion will continue, mostly in unspoiled coastlines that are particularly extensive in Asia and Africa,” Vousdoukas concluded. “Therefore, adaptive measures are urgently needed.”

In the United States, there is no clear set of directions, no one-size-fits-all solution. The big dilemma revolves around what should be sacrificed: either man-made development, sitting on beachfronts or on top of cliffs, or the beach along the shore. The choice involves hard math and a trade-off between economic and environmental values, and between private interests and the public good.

Large numbers of homes at risk

A recent analysis by Climate Central, an independent U.S.-based organization of scientists and journalists reporting on the impact of climate change, shows that in the most optimistic climate change scenario, nearly 20,000 homes built in the past decade along the U.S. coasts will be exposed to flooding by 2050. If greenhouse gases and sea level rise are not curbed, the number of homes at risk will jump to 800,000 (at a valuation of $451 billion) by 2050 and to 3.4 million (worth $1.75 trillion) by 2100. In California alone, more than $150 billion in property could be wiped away. Seawalls are one option to protect homes and strategic infrastructure, but they disrupt the natural replenishment of sand, helping to wash away beaches until they vanish altogether. For every new seawall protecting a home or a road, a public beach is sacrificed.

To counter these unintended consequences, some states (examples include Oregon, North Carolina, and Maine) have banned new seawalls. Others have imposed significant restrictions.

In Malibu’s Broad Beach, sand was disappearing so rapidly in the 2000s that a rock wall was built in 2010 to protect those homes built right on the beach from flooding. Today, there is just a tiny strip of sand visible during high tide.

According to a U.S. Geological Survey study published in July 2018, without the supply of sand from eroding cliffs, beaches in the whole of Southern California may not survive rising sea levels. At the same time, cliff-top development is unlikely to withstand the 62 to 135 feet of cliff recession forecast by 2100.

One alternative way to provide a degree of protection for both beaches and properties is to add sand to the seashore, to preserve a natural buffer zone between the sea and man-made constructions. But erosion continues, because sand is always moving. Depending on how fast a beach retreats, refurbishing projects have to be repeated every few years.

Carolina Beach, in North Carolina, has been replenished 31 times since 1955. In 2001, San Diego County pumped about two million cubic yards of sand from offshore onto 12 beaches, which then narrowed significantly by the following year.

Beach-nourishing projects can keep rolling as long as money is available and there is enough sand, which is neither limitless nor free. Sand is one of the world’s most exploited and widely consumed natural resources. Federal agencies, states, cities, and private companies are all competing to get permits to extract the precious grains from the seabed or from mines.

The U.S federal coffers have spent some $9 billion to rebuild beaches along the two coasts since 1923. Annually, Congress budgets $50 million to $70 million for beach replenishment, about one-third of which is spent on Florida’s 200-mile beach coastline, the longest of any mainland state, to protect that state’s $67 billion tourism industry.

Beach replenishment projects are co-funded by local administrations and the federal government, which usually pays 65 percent for the first application. Repeat applications are generally split 50–50 with the U.S. Corps of Engineers, the federal agency that is also tasked with managing flood risk across America.

Public funding benefits private property

As a general rule, the consensus among decision-makers is that the profitable shorelines are the ones most worth saving. Beach nourishment initiatives are mainly carried out to mitigate future flooding, protect valuable oceanfront properties, and boost local economies that rely on tourism. And indeed, newly nourished beaches suffer less erosion after storms than nonreplenished beaches.

Two decades ago, a study by the Howard Marlowe American Coastal Coalition projected that every five years, coastal erosion would cost beach tourism an estimated $30.2 million in lost consumer revenues.

However, through replenishing the same areas again and again, such initiatives end up disproportionately benefiting a small number of usually wealthy communities. An investigation by Pro Publica in 2018 explained that the Corps prioritizes projects that ensure the highest benefit, in terms of saved property values, measured against the cost of the projects. This practice tends to favor areas more densely populated by high-income property owners, since lower-income towns have a harder time meeting those criteria and have too low a tax base to manage the cost by themselves.

Statistics about past and ongoing beach-restocking expenditures offer an indication of what taxpayers should expect to pay to save at least some stretches of the nation’s sandy shoreline in the years to come. These figures include: $828 million spent in North Carolina since 1939; $21.5 million budgeted in Virginia Beach for the new project started in November 2019; roughly $100 million disbursed annually in Florida (derived from aggregate state, local, and private funding sources); and $65 million projected to save Malibu’s Broad beach.

According to some land-use consultants, rather than pursuing seawalls or sand replenishment projects, the more cost-effective and longer-lasting solution would be to locate coastal development further inland. This option is technically called “managed retreat.”

Supporters of this option argue that relentless efforts to reverse beach erosion create a vicious circle, by encouraging additional building along the shore, thus putting more people and public resources at risk. With the likelihood of increasing liability, insurers may decline to cover risky properties, and the state would become the last resort.

Still, without a clear mandate for managed retreat and in the absence of a public funding plan, there is currently no incentive for developers and homeowners to consider this option.

A recent simulation study, conducted in Oregon’s Tillamook County by that state’s Climate Change Research Institute, has shown that the implementation of inland relocation policies would save a considerable share of residential and commercial properties that would likely be lost to chronic erosion.

Managed retreat offers potential solutions

Managed retreat could further reduce the risk of flooding at the ground level through the deployment of elevated buildings, so that rising water would not reach the living space. This solution was suggested by the National Institute of Building Sciences in a 2018 report commissioned by the Federal Emergency Management Agency.

Even as the sea moves inland with ever-increasing speed, state and local administrations continue to lobby Congress through the American Shore and Beach Preservation Association for increased public funding for beach restoration and for ongoing federally backed insurance programs. These guarantees are needed by county and municipal authorities to bolster coastal development. Indeed, such investments would be less attractive absent government plans to preserve the beachfront.

With the coronavirus-induced economic slowdown, fuel consumption and greenhouse gas emissions have been reduced. The virus, ironically, has temporarily provided a window onto what full-scale mitigation of global warming would look like. Yet in the wake of the pandemic, with governments aggressively boosting economic recovery, emissions will likely increase to even higher levels than those recorded before the outbreak. As a result, the more severe coastal erosion projections associated with climate scenarios containing the least amount of mitigation will become, in Jonathan Schell’s memorable coinage, the fate of the earth.

Stefano Valentino is the founder of MobileReporter, an environmental-focused investigative storytelling platform, and a member of the European Data Journalism Network.

 


source: Joint Research Centre of the European Commission

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