More Than Half A Million People At Risk Of Repeated Flooding Across 32 US Coastal Cities Due To Rising Sea Level

A new study found that sinking ground and rising sea levels would put more than 500,000 people in 32 coastal cities in the United States at risk of frequent floods.

If nothing is done to mitigate the risk, the deluges might cost $107 billion in damages by 2050.

Sinking Of Land

Coastal communities frequently experience subsidence-the progressive sinking of land over time. One of the most important drivers of this is the extraction of resources from the ground, such as water and fossil fuels, which causes the earth to compact.

According to a study published in the journal Nature, as oceans rise and coasts sink, up to 343,000 acres of land may be exposed to devastating flooding by 2050, caused by threats such as hurricanes, coastal storms, and shoreline erosion.

In the worst-case scenario, approximately one in every fifty residents in the 32 cities studied could be exposed to flood risks.

To study how subsidence and rising sea levels may influence coastal areas, Virginia Tech's Leonard Ohenhen and colleagues developed a model based on land elevation changes and anticipated sea level rise to 2050 for 32 major waterfront cities, including Boston and San Francisco.

The researchers discovered that cities around the Atlantic and Gulf of Mexico coasts, such as New Orleans, had lower heights and higher rates of subsidence, sinking at least 2 mm more per year than cities in other regions, posing a larger risk of future flooding.

Because of their higher elevation, urban centers along the Pacific coast are more protected against sea-level rise.

Climate change has been melting glaciers and heating ocean water during the twentieth century, causing the water to expand and sea levels to rise at a rate of around 0.13 inch (3.4 millimeters) per year over the last 30 years.

The land in coastal areas is sinking due to a perfect storm of factors: metropolises are growing taller and heavier, coastal land is shifting downward after the end of the last ice age, and gas, water, and other materials have been lifted en masse from below ground, hollowing out the land beneath cities.

US Flood Defenses

The study also shows that current estimations of flood risk in the United States, which do not account for the compounding effect of subsidence, underestimate the threat.

Team member Manoochehr Shirzaei, who is also at Virginia Tech, said these findings underline the critical need to bolster US flood defenses right now.

"Individual cities will need to take different adaptation measures. For New Orleans, flood defences should be upgraded for the entire city, while San Francisco probably needs to just defend important infrastructure," he added.

Ohenhen highlighted that major investment in both structural defenses and subsidence control measures is necessary.

The economic implications of such investments must be balanced against the potential costs of inaction, which could result in significantly higher economic and societal consequences.

And subsidence isn't simply a problem in the United States.

Sinking land due to groundwater extraction is anticipated to harm 19% of the world's population by 2040, and humans have even extracted enough water to alter the Earth's tilt.

Indonesia's government has stated that it will relocate its capital from Jakarta (home to 11 million people) to Borneo after the megacity sank more than 8 feet (2.5 meters) over the last decade.