The Mississippi Delta region of Louisiana is experiencing a combination of rising seas and subsiding land. The result: shorelines are sinking into the ocean. Roads, facilities, and indeed, whole communities are being washed over by the encroaching sea. One visually striking example is the fate of dozens of small-town cemeteries in coastal villages. Bit by bit, gravesites along the shore, once high and dry, are slipping into the water.
USA Today carried a slideshow with photos of the slowly disappearing graveyards (“Louisiana’s sinking cemeteries”). <i>The Huffington Post</i> also has the slideshows, along with a story (“Louisiana Cemeteries Sinking Along The Gulf Coast, Washing Away,” by Stacy Plaisance).
But the problems of the Gulf shore are much bigger than just the loss of some graves. At the “Climate.gov” website of the National Oceanic and Atmospheric Administration (NOAA), a long report places the cemeteries in a broader context: the ongoing challenge to the south Louisiana coastal society and economy from the combination of ground subsidence and sea level rise. While sea levels worldwide have risen less than a foot in the past century, the water along the Mississippi Delta is now close to three feet higher than a century ago, when compared with the elevations on shore (“Thriving on a Sinking Landscape,” by Caitlyn Kennedy). Benchmarks placed to aid in map surveys decades ago are now submerged beneath salt water, and over the years, homes and workplaces have disappeared — or, if still above water, are lapped by waves and vulnerable to frequent flooding from small storms.
Combining text, photos, and video, the six-page report details the effects of the sinking ground and rising sea on the people and the critical industries located at the mouth of the MIssissippi (which includes a significant segment of the U.S. oil and gas industry). Part of the story discusses the effort to raise roads above the sea: below, photos show a stretch of critical road that sits only inches above the Gulf, and another stretch of the same highway that has been re-engineered to withstand hurricane storm surge even after the predicted rise in sea levels in the coming century. The story also details the advanced GPS technology scientists are using to keep track of the changing land and ocean, giving engineers the data they need to design structures for a 75-year or longer lifespan even as conditions change.
Louisiana’s shoreline is an extreme case. The combination of ground subsidence and sea level rise there is unusual: nowhere else in the world have local sea levels risen so sharply in the last century. But climate scientists and oceanographers are warning that similar sea level rises of three feet or more are not unlikely in the coming century for the entire Atlantic and Gulf Coast shoreline, a product of melting ice sheets and expansion of the warming oceans. If that scenario comes to pass, the experience of the Louisiana shore will offer important lessons for shore regions in the rest of the country.