44 JANUARY/FEBRUARY 2018 • FOGHORN NEWSWIRE Accumulating sediment within the lower Mississippi River could, when coupled with a major flood, cause the river to abandon its current course, potentially ruining the drinking water source for roughly 1.5 million people, according to new research presented in New Orleans on December 12, 2017 at the annual American Geophysical Union fall meeting. TheAmerican Geophysical Union is a not-for-profit, professional, scientific organization representing more than 60,000 members in 139 countries. The Mississippi River is an alluvial river, meaning its course is shaped by sediment and floods, and its floor is composed of loose, moving sands and soils. Because of these qualities, the river naturally changes course every 1,000 to 1,500 years. The Old River Control Structure, a 54-year-old floodgate system, manages the flow of the Mississippi into the Atchafalaya River, which runs parallel to and west of the Mississippi. This system prevents the Mississippi from flooding and changing its course. In the new research, scientists took measurements of sediment accumu- lating downstream of the Old River Control Structure to the Gulf of Mexico, a total of more than 300 miles. The floodgate system regulates the flow of water, but it does little to address sediment moving downstream in the Mississippi, where this sediment accu- mulates when the river’s flow naturally slows, according to the researchers. The new research finds sediment has caused the river floor down- stream of the floodgate to elevate and the sandbars to grow in volume by more than 200 percent. At least 36 million metric tons of coarse sand has been added to the river and narrowed the river channel by half a mile, according to hydrologist Yi-Jun Xu from Louisiana State University in Baton Rouge, who presented the new findings. Xu’s previous research found these sandbars could swell even larger in the near future, as sand has also ac- cumulated upstream from the control structure and could wash downstream under the right conditions. These changes diminish the river’s capacity to carry water on its current course. When sections of the river’s floor rise to a sufficient point, a sudden increase in flow — perhaps from a flood — could drive the Mississippi River to overwhelm the control structure and adopt a new path, potentially causing Study Warns Accumulating Sediment in Mississippi River Threatens Course Change, Water Supply We NY, too! We NY, too!