resilient flood infrastructure in south louisiana
Every flood year, the Old River Control Structures that regulate Mississippi distribution into the Atchafalaya are threatened, risking a catastrophic switch in river course that would leave New Orleans without fresh water or a functioning port. This research suggests that the conditions for Mississippi avulsion have been constructed through a delta management paradigm which promotes river degradation to maintain navigation and flood relief; if we wish to maintain the existing channel, we must develop a new spillway typology which promotes aggradation at Old River during flood events.
Levee Pruning opportunistically utilizes the alluvial landscape and political infrastructure above the Old River Control Complex as a new spillway, mitigating degradation of the Old River Outfall Channel and reducing strain on Control Structures. Levees are lowered and widened so that the Mississippi gradually spills over as sheet flow during flood stage, creating a resilient flood diversion that is gradually activated based on the needs of Baton Rouge and below, growing stronger with sediment each year.
The controlled 70/30 split in flow distribution rewards certain uses and sacrifices others. Challenging this historic ratio requires a critical understanding of the basinwide effects of variable flow, maintaining sufficient freshwater through Old River for navigation and swamp ecology, while reserving the super levee spillway for flood relief. To evaluate a possible floodpath through Old River, an exaggerated terrain model was digitally fabricated and several levee cuts were tested, indicating instant relief at control structures by diverting the Mississippi to backwater flood zones first during extreme events. Additional distribution through a high water channel system could begin as early as Simmesport.