71.5% of U.S. coastlines are subsiding

Tufts University and Virginia Tech researchers analyzed more than 190 million measurements from the 2007‑2020 period to study ground movements along U.S. coastlines.

Satellite‑based data revealed that the ground is moving downward over most of the country's coastline. In 43% of the coasts, annual subsidence exceeds 2 millimetres, and in 23.3% it surpasses 3 millimetres.

The highest subsidence rates were observed along the Gulf of Mexico coast, while significant ground loss was also detected across much of the Eastern Shore. In some sections of the western coast, the ground was found to be rising.

Groundwater extraction also plays a role.

Researchers say that both natural and anthropogenic factors jointly contribute to coastal subsidence.

The compaction of soft sediments over time and geological movements left over from the last glacial period are among the natural causes, while excessive groundwater use accelerates subsidence in some areas.

84 million people live in risk areas

According to the study, in coastal areas where subsidence is observed at low levels, 67.1 million people live, at medium levels 14 million, and at high levels 3.2 million.

Thus, the total population living in coastal areas with varying levels of subsidence reaches about 84.3 million.