Future Mississippi River

the old river control structure complex. view east-southeast, looking downriver on mississippi, 3 dams across channels of atchafalaya river right of mississippi. concordia parish, louisiana in foreground, on right, , wilkinson county, mississippi, in background, across mississippi on left.

the old river control structure, between present mississippi river channel , atchafalaya basin, sits @ normal water elevation , ordinarily used divert 30% of mississippi s flow atchafalaya river. there steep drop here away mississippi s main channel atchafalaya basin. if facility fail during major flood, there strong concern water scour , erode river bottom enough capture mississippi s main channel. structure lost during 1973 flood, repairs , improvements made after engineers studied forces @ play. in particular, corps of engineers made many improvements , constructed additional facilities routing water through vicinity. these additional facilities give corps more flexibility , potential flow capacity had in 1973, further reduces risk of catastrophic failure in area during other major floods, such of 2011.

because morganza spillway higher , river, dry on both sides. if failed @ crest during severe flood, flood waters have erode normal water levels before mississippi permanently jump channel @ location. during 2011 floods, corps of engineers opened morganza spillway 1/4 of capacity allow 150,000 ft/sec of water flood morganza , atchafalaya floodways , continue directly gulf of mexico, bypassing baton rouge , new orleans. in addition reducing mississippi river crest downstream, diversion reduced chances of channel change reducing stress on other elements of control system.

some geologists have noted possibility course change atchafalaya exists in area north of old river control structure. army corps of engineers geologist fred smith once stated, mississippi wants go west. 1973 forty-year flood. big 1 lies out there somewhere—when structures can t release floodwaters , levee going have give way. when river s going jump banks , try break through.

another possible course change mississippi river diversion lake pontchartrain near new orleans. route controlled bonnet carré spillway, built reduce flooding in new orleans. spillway , imperfect natural levee 4–6 meters (12 20 feet) high prevents mississippi taking new, shorter course through lake pontchartrain gulf of mexico. diversion of mississippi s main channel through lake pontchartrain have consequences similar atchafalaya diversion, lesser extent, since present river channel remain in use past baton rouge , new orleans area.