"We're essentially putting a straitjacket on the river itself, disconnecting the river from the surrounding environment and preventing these natural exchange processes," Nittrouer said. "Because we build communities along these rivers, we build levee systems that corral all that water and sediment and take it straight to the Gulf of Mexico."
What caused such a large percentage of sand to divert to the spillway in such a small amount of water? The researchers believe that the local conditions at that point in the river hold the answer. The spillway is on the inside of a bend and adjacent to a sandbar.
"That acts as a means of allowing for sustained high-concentration sandy water to be positioned very near the spillway itself, so that sediment-enriched water is now spilling into the floodway and that sediment is depositing out," Nittrouer said.
Now, the researchers will further explore how local river conditions could favor the movement of sediment from the river into the neighboring wetland spillway. They plan to use modeling and lab studies to find optimal conditions that could shunt sediment out of the river, with the eventual goal of designing other spillways that could be opened strategically to rebuild lost wetlands without flooding residential areas.
|Contact: Liz Ahlberg|
University of Illinois at Urbana-Champaign