The wetlands of the Mississippi River Delta are slowly sinking and rapidly eroding, but new research has found the river’s supply of sand — the material engineers most need to rebuild the delta — will stay constant for centuries. “It’s true that the total amount of sediment has diminished, but river sediment contains both fine-grained mud and course-grained sand, and our research found that upstream dam construction has not reduced the amount of sand in the lower Mississippi and won’t for at least 300-600 years,” said study’s lead author.