Morganza Spillway

Morganza Spillway
Name	Morganza Spillway
Location	Pointe Coupee Parish, Louisiana, United States
Coordinates	30°58′N 91°35′W
Operator	United States Army Corps of Engineers
Opening	1954
Type	Spillway
Reservoir	Atchafalaya Basin

Contents

Morganza Spillway is a flood-control structure on the Mississippi River in Pointe Coupee Parish, Louisiana, constructed and operated to divert high flows from the Mississippi into the Atchafalaya Basin and ultimately the Gulf of Mexico. It functions as a complementary facility to the Bonnet Carré Spillway and the Old River Control Structure within the Mississippi River and Tributaries Project, aiming to protect population centers such as Baton Rouge and New Orleans by reducing river stages. The spillway has been opened only a few times since completion, most notably in major high-water crises that engaged federal, state, and local agencies including the United States Army Corps of Engineers, the Secretary of the Army, and regional emergency management authorities.

Description and Purpose

The Morganza facility sits near the town of Morganza, Louisiana and channels excess floodwaters through the Atchafalaya Basin to relieve pressure on the main Mississippi River channel. Engineered as part of the broader Mississippi River and Tributaries Project authorized after catastrophic floods, its purpose parallels that of the Bonnet Carré Spillway near St. Charles Parish, Louisiana and the Old River Control Structure near Simmesport, Louisiana. The spillway protects industrial assets along the river such as facilities in the Petrochemical Company corridors in Plaquemine, Louisiana and Baton Rouge and safeguards military installations like Camp Beauregard and regional infrastructure including Interstate 10 and US Route 61. Operation decisions involve coordination with the Federal Emergency Management Agency, the Governor of Louisiana, and regional floodplain authorities.

Planning for the Morganza Spillway followed catastrophic floods including the Great Mississippi Flood of 1927 and subsequent federal responses embodied in the Flood Control Act of 1928 and later amendments. The spillway was designed during mid-20th-century work led by the United States Army Corps of Engineers with construction completed in the early 1950s and official activation in 1954. Its development involved partnerships with state agencies such as the Louisiana Department of Transportation and Development and local parishes including Pointe Coupee Parish and St. Landry Parish. Construction impacted historical settlements along the basin and intersected issues addressed in cases like Missouri v. Illinois and interstate water management discussions referenced in hearings before the United States Congress.

Morganza comprises a gated concrete-weir system with movable spillway structures that funnel excess flow from the Mississippi River into a controlled channel leading to the Atchafalaya River and eventually the Gulf of Mexico. It is part of the engineered network including the Old River Control Structure and the Bonnet Carré Spillway and works in conjunction with levees managed by the New Orleans District, United States Army Corps of Engineers. Operation thresholds consider stages at monitoring points such as Red River Landing and Angola, Louisiana, and are informed by hydrologic modeling from institutions like the United States Geological Survey and the National Weather Service. Decision-making integrates inputs from the National Oceanic and Atmospheric Administration, the National Aeronautics and Space Administration for remote sensing, and regional authorities such as Entergy Corporation for infrastructure resilience.

The spillway has been opened in limited circumstances, most notably during the Great Flood of 1973 and the Mississippi River floods of 2011 when the United States Army Corps of Engineers authorized its use to lower stages at Vicksburg, Mississippi and protect cities like Baton Rouge and New Orleans. Openings require coordination with downstream communities in the Atchafalaya Basin including Simmesport, Louisiana and Morgan City and impact navigation along the Lower Mississippi River governed by the United States Coast Guard and the American Waterways Operators. During activations, emergency responses have involved the Federal Emergency Management Agency, the Louisiana National Guard, and nonprofit organizations such as the American Red Cross and The Nature Conservancy.

Diverting Mississippi waters through Morganza alters hydrology, sediment transport, and ecology in the Atchafalaya Basin, affecting wetlands protected under state programs and federal statutes including those administered by the United States Fish and Wildlife Service. Impacts extend to fisheries in the Gulf of Mexico, commercial shrimping fleets operating from ports such as Berwick, Louisiana and Morgan City, Louisiana, and to agricultural lands in Pointe Coupee Parish. Economic considerations balance protection of petrochemical complexes near Baton Rouge and Plaquemine, Louisiana against habitat loss in areas managed by organizations like the Louisiana Department of Wildlife and Fisheries and conservation groups including Audubon Society. Environmental reviews have referenced analyses by the Environmental Protection Agency and studies published by universities such as Louisiana State University and Tulane University.

The United States Army Corps of Engineers maintains the Morganza Spillway, performing periodic inspections, repairs, and upgrades in collaboration with the New Orleans District and national authorities such as the Assistant Secretary of the Army (Civil Works). Maintenance activities coordinate with state agencies including the Louisiana Department of Transportation and Development and local parishes, and funding arises from congressional appropriations under legislation like the Water Resources Development Act. Long-term management planning considers climate variability assessed by the National Climate Assessment and infrastructure resilience frameworks promoted by the Federal Emergency Management Agency and the United States Department of Transportation.