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Title: Morganza Floodway : soft opening scenarios
Authors: Clifton, Nathan D.
Lewis, James W.
Abraham, David D.
Bell, Gary L.
Keywords: Mississippi River
Flood control
Morganza (La.)
Hydraulic models
Publisher: United States. Army. Corps of Engineers. Mississippi Valley Division.
United States. Mississippi River Commission.
Coastal and Hydraulics Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: MRG&P ; Tech Note No. 6
Abstract: The Morganza Control Structure (MCS) is an important water management feature of the Mississippi River and Tributaries System. During extreme high-flow events, when the discharge past Baton Rouge is expected to exceed 1,500,000 cubic feet per second (cfs), water is diverted through the MCS, out of the Mississippi River in the vicinity of river mile 280, and into the Morganza Floodway to reduce the flow going past Baton Rouge and New Orleans. Completed in 1954, operation of the MCS has only occurred during the floods of 1973 and 2011 (USACE 2012). The Morganza Floodway is the area immediately downstream of the MCS, which hydraulically connects the diverted flow to the Atchafalaya River basin. The widespread flooding within the Morganza Floodway during the 2011 Mississippi River Flood negatively affected wildlife. According to Section V of the Post-Flood Report (USACE 2012), ground-dwelling animals such as turkeys, deer, rabbits, armadillos, feral hogs, and bobcats attempt to flee floodwaters. Natural flooding events of bottom land hardwood forests see floodwaters rising on the order of inches per day, during which ground-dwelling animals search for higher ground. During 2011, floodwater depths occasionally increased on the order of feet per day, which resulted in observed animal fatalities. According to a study by Chamberlain et al. (2013), flow through the Morganza Floodway in 2011 negatively affected wild turkey populations through direct reductions in survival. Out of five tagged wild turkeys, only one survived to reach dry ground. On the other hand, black bears, which were recently delisted as an endangered species in 2016, were shown to be minimally affected by the 2011 flood (O’Connell-Goode et al. 2014). Approximately 89% of the black bears remained within the flooded area. During the flood, black bears denned up in trees and fasted for the duration of the flooding event. One female was struck by a train during the event, and it is presumed her cubs were lost as well (O’Connell-Goode et al. 2014). The Morganza Floodway primarily consists of forest and agricultural lands. O’Connell-Goode et al. (2014) used barbed-wire hair sites to monitor black bears throughout the entire Morganza Floodway from Louisiana Highway 1 to U.S. Highway 190. In addition to wildlife living throughout the area, there is also a significant amount of agricultural (soybeans, corn, milo, sugarcane, etc.) and cattle production. The investigation used the existing numerical model of the Morganza Floodway by Bell et al. (2017). The numerical code employed is the two-dimensional Adaptive Hydraulics (AdH) code. The Bell et al. (2017) model of the floodway was developed to accurately resolve the flood of 2011; all simulated water surfaces were within 1 foot (ft) of measured gage water surfaces for all gage locations. More detailed information about the development of the AdH model can be found in Bell et al. (2017). The purpose of this study was to simulate the timing and extent of lower discharge flooding events into the Morganza Floodway. These lower discharge events are referred to as soft opening and are intented to gradually fill the floodway providing wildlife an evacuation period from the area before high flow releases.
Description: MRG&P Tech Note
Gov't Doc #: MRG&P Tech Note No. 6
Rights: Approved for Public Release; Distribution is Unlimited
Size: 11 pages/6.578 Mb
Appears in Collections:Technical Note

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