(WVUE) - When the state pumped millions of cubic yards of sand and dirt onto a Louisiana beach a couple years ago, the beach later sank.
A new LSU study finds the sheer weight of the sand compacted the earth below the Caminada Headland, causing the beach to subside by as much as 1 foot in one year.
"When you add sediments, there's a response," said LSU coastal scientist Harry Roberts, who led the team of researchers. "And that response is, really, pretty quick."
While the sinkage was expected, the rate of loss caught researchers by surprise.
"It was more than we had expected," Dr. Roberts said.
The $200 million Caminada Headland project ranks as one of the largest restoration efforts Louisiana has undertaken. The study examined the results after the state took 3.3 million cubic yards of sand from Ship Shoal, an ancient barrier island now submerged in the Gulf of Mexico. The project had raised the dune along the beach to 7 feet - 3 feet higher.
The Coastal Protection and Restoration Authority considers the headland critically important as the first line of storm defense for the nearby oil and gas hub of Port Fourchon. Roberts hopes the study, funded by CPRA, will continue over the next several years to allow scientists and planners to learn more about the effects of piling land onto marsh or barrier islands.
In a statement to the Associated Press, CPRA Chairman Chip Kline said engineers predicted the compaction from the weight of the sand and accounted for that in their designs.
"The bottom line is that we predicted the subsidence and overbuilt to accommodate the settlement," Kline said in the statement.
Although Roberts said the sinkage will trail off over time, he expects the beach to sink about 2 feet over a 20-year period.