Mississippi River channel response to the Bonnet Carre Spillway opening in the 2011 flood and its implications for the design and operation of river diversions

摘要: Summary The large Mississippi River flood in 2011 was notable the lowermost Louisiana, USA reach for requiring operation of several control structures to reduce stress on artificial levees: largest diversion went through gated Bonnet Carre Spillway, which opened 42 days May and June. removal approximately 20% total discharge from river provided an opportunity examine impact water sediment transport capacity rivers. Boat-based, acoustic bed sampling surveys were conducted channel adjacent Spillway immediately prior opening structure, at full capacity, following (June 2011) 1 year after 2012) closure. designed (1) elevation change due scour or aggradation sediment, (2) suspended bedload variability upriver downriver Spillway. results indicate that 9.1 million tons sand deposited exit pathway extending least 13 km a rapidly progressively reducing magnitude per kilometer. surficial deposit finer grain size than lateral bars structure. We argue largely delivered suspension derived observed deflation upstream point, rather arriving drainage basin. Approximately 69% removed downstream between June 2012. conclude source reduction stream power, and, thus, Mississippi, associated with withdrawal. re-entrainment this material year indicates system re-establishes equilibrium pre-opening conditions. Future diversions coastal restoration will have address issue maintain deep draft navigation River.