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The HEC-6T one-dimensional numerical sedimentation model was used to evaluate the long-term and system-wide sedimentation effects of modifying the operation schedule at the Old River Control Complex (ORCC). The changes evaluated were increasing and decreasing the percentage of flow that is diverted to the Atchafalaya River from the Mississippi River at the ORCC and modifying the distributions through the four ORCC structures. Sedimentation effects for several operation scenarios were compared to a Base Condition that represented the existing operation protocols. Additionally, a dredging scenario was developed and analyzed. This scenario featured dredging material from the Mississippi River and depositing it into the Outflow Channel, downstream of the ORCC. The predictive simulations extended for 50 years. The model was used to calculate and compare sand transport past various gages along the Atchafalaya River. Also, the model compared differences in water surface elevations and bed elevations using a specific gage analysis at several gages along the Atchafalaya River. Last, the effects of the various scenarios on annual dredging requirements in Berwick Bay were also determined. |
