Mississippi River and Tributaries Flowline Assessment: Atchafalaya River Sedimentation Model Report
ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS VICKSBURG United States
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A HEC-6T numerical sedimentation model study was conducted to determine the effects of long-term sedimentation processes on the Project Design Flood PDF flowline for the Atchafalaya River. The upstream extent of the model was the confluence of the Red River and the Old River Control Complex outflow channel, approximately 8.5 miles upstream of Simmesport, LA. There were two downstream ends of the model each extended to the Gulf of Mexico, one for the Wax Lake Outlet and one for the Lower Atchafalaya River. The model was built from a previous study performed in 2010 using 1997 geometry. The calibration time period was 1997 to 2010, and bed elevations were compared with a 2010 bathymetric survey. The model was validated by simulating the years 1997 through 2016. Then the model simulated 50 years, from 2017 to 2066. Average bed changes were provided to the HEC-RAS model. The model incorporated the Morganza Control Structure flows, dredging, subsidence, and sea level rise. Model results showed that the Wax Lake Outlet is capturing an increasing amount of flow from the Lower Atchafalaya River, and the PDF scours the channel bed elevations during the rising limb of the hydrograph, especially near Morgan City.
- Hydrology, Limnology and Potamology