Washington, D.C. is sinking, and could drop by 15 centimeters (6 inches) in the next 100 years. The sinking land makes the nation’s capital even more vulnerable to flooding as sea levels are expected to rise.
The new findings, published in the journal GSA Today, confirm what geologists have hypothesized for decades about Chesapeake Bay. The sea level in the Chesapeake has been rising at twice the global average for the last 60 years. Geologists suspected that this was a remnant of the last ice age due to a phenomenon known as “forebulge collapse.” The weight of a prehistoric ice sheet to the north had been pushing up the land in this area, but as the ice sheet began melting away 20,000 years ago the bulged-up area started to sink back.
“It’s a bit like sitting on one side of a water bed filled with very thick honey,” said Ben DeJong, the lead author of the new study, in a statement, “then the other side goes up. But when you stand, the bulge comes down again.”
Researchers were able to confirm this hypothesis with an extensive field study in which they drilled 70 boreholes – sometimes a hundred feet deep – in the Blackwater National Wildlife Refuge on the Chesapeake’s eastern shore. This allowed researchers to get a better understanding of the geological process that dates back several million years. Researchers combined sediment data with high-resolution maps to create 3D portraits of the land sinking. They were even able to paint a clearer picture of how the sinking will continue. Researchers predict that Washington, D.C. could sink by 15 centimeters (six inches) in the next century.
While 15 centimeters may not sound like much, it’s a sobering conclusion when combined with the average global sea level rise. This rise in sea level isn’t likely to be equal across the globe, with scientists previously showing that sea level rises in the Atlantic were already three to four times higher than the global average.
In short, Washington, D.C. is particularly vulnerable to flooding, threatening its monuments and wildlife refuges. Researchers point out that the land sinking is not predominately driven by human influence, but long-term geological processes. So for once it’s not completely our fault. It is vital, however, that policymakers respond, researchers say.
“It’s ironic that the nation's capital – the place least responsive to the dangers of climate change – is sitting in one of the worst spots it could be in terms of this land subsidence,” said Paul Bierman, senior author on the new paper. “Will the Congress just sit there with their feet getting ever wetter? What’s next, forebulge denial?”