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Morganza Floodway

Intended to operate during emergency flooding, the purpose of the Morganza Floodway is to divert excess floodwater from the Mississippi River into the Atchafalaya Basin. The floodway consists of two structures – the Morganza Control Structure and the Morganza Floodway – which are designed to pass up to 600,000 cubic feet per second (cfs) of water to the Gulf of Mexico, alleviating stress for mainline levees downstream along the Mississippi River.

Located at river mile 280 in central Louisiana, the Morganza Floodway begins at the Mississippi River, extends southward to the East Atchafalaya River levee, and eventually joins the Atchafalaya River Basin Floodway near Krotz Springs, Louisiana. Seven design plans were originally proposed, and a two-structure design was selected. Construction of both structures was completed in 1954. The first component at Morganza is the floodway. At twenty miles long and five miles wide, it consists of a stilling basin, an approach and outlet channel, and two guide levees. The second element is a control structure containing a concrete weir, two sluice gates, seventeen scour indicators, and 125 gated openings.

The decision to open the Morganza Floodway relies on current and projected river flows and levee conditions, river currents and potential effects on navigation and revetments, extended rain and stage forecasts, and the duration of high river stages. When river flows at the Red River Landing are predicted to reach 1.5 million cfs and rising, the Corps considers opening the Morganza Floodway.

Every year, written notices are issued to all interests reminding them of the possibility of operation of the floodway. In the event that Morganza needs to be opened, the USACE project managers, along with news media and civil officials, will help notify all interested parties as soon as possible. On receipt of such notice, expeditious action must be taken as soon as possible to protect life and property. If the Morganza Floodway is operated, there is a possibility that personal property will be flooded. In the event of an opening, all water and/or gas wells must be sealed and capped to prevent contamination from floodwaters.

The Morganza Floodway was partially operated during the 1973 high water event to relieve pressure on Old River’s Low Sill Structure. Overall, the spillway structure fared well with minor scouring and slight damage to the stilling basin. Repairs have since taken place and the structure has been restored to its original state. Inspections are ongoing to ensure that the structure operates correctly in the event of an opening



2011 Morganza Floodway Proposed Clarifications to Standing Instructions

Based on lessons learned from the historic Mississippi River Flood of 2011, the U.S. Army Corps of Engineers, New Orleans District is releasing proposed clarifications to the standing instructions for operation of the Morganza Control Structure during a flood event.  The Corps is releasing these proposed clarifications for a 30-day public review period and will host several public meetings to gather public input. 

The proposed clarifications to the standing instructions will help ensure safe operation of the Morganza Control Structure during a flood event and prevent unnecessary stress on mainline Mississippi River levees.  As proposed, the Morganza Control Structure would be operated when a 10-day forecast projects a Mississippi River flow of 1.5 million cubic feet per second and rising past the structure.  The structure would be operated to maintain a water stage of 57 feet on the river side of the structure and a Mississippi River discharge rate that does not exceed 1.5 million cubic feet per second below the floodway.

The U.S. Army Corps of Engineers learned important lessons from 2011 regarding the safe operation of the Mississippi River and Tributaries System and the Morganza Control Structure.  The Corps’ goal for operation is to pass the project flood through the Mississippi River and Tributaries System safely, while reducing unnecessary stress on the flood control structures and the mainline MR&T levees.  In the event that the Morganza Control Structure needs to be operated, the Corps will coordinate all emergency operation efforts with our federal, state and local partners before, during and after such events.

Please contact the New Orleans District, Public Affairs Office for more information at AskTheCorps@usace.army.mil or 504-862-1759. Hard copies of the proposed clarifications to the standing instructions can be mailed upon request.

 

Public meeting details are:

When:  Tuesday, September 23, 2014

6:00 to 6:30 p.m. – Open House
6:30 to 8:30 p.m. – Presentation, Question and Answer Session

Where: St. Martinville

St. Martin Parish Government Building, 301 West Port St., St. Martinville, LA 70582

 

When:  Tuesday, September 30, 2014

6:00 to 6:30 p.m. – Open House
6:30 to 8:30 p.m. – Presentation, Question and Answer Session

Where: Morgan City

Morgan City Auditorium, 728 Myrtle Street, Morgan City, LA 70380

 

When:  Thursday, October 2, 2014

6:00 to 6:30 p.m. – Open House
6:30 to 8:30 p.m. – Presentation, Question and Answer Session

Where: Baton Rouge

Capitol Park Welcome Center, 702 River Rd., Baton Rouge, LA 70802

Morganza Floodway Opening Pace: 2011

Morganza Floodway Opening Pace: 2011
 
2011 Date
Bays Opened
Total Opened 2011
Discharge (CFS)
Day 1

May 14

2

2

21,000

Day 2

May 15

7

9

96,000

Day 3

May 16

6

15

158,000**

Day 4

May 17

1

16

170,000

Day 5

May 18

1

17

182,000

Day 6

May 19

0

17

179,000

Day 7

May 20

0

17

179,000

Day 8

May 21

0

17

178,000

Day 9

May 22

0

17

175,000

Days 10

May 23

0

17

173,000

Days 11

May 24

-1

16

160,000

Days 12

May 25

-2

14

140,000

Days 13

May 26

-2

12

121,000

Days 14

May 27

0

12

120,000

Days 15

May 28

0

12

119,000

Days 16

May 29

-1

11

109,000

Days 17

May 30

-1

10

98,000

Days 18

May 31

0

10

97,000

Days 19

Jun 1

-1

9

86,000

Days 20

Jun 2

-1

8

76,000

Days 21

Jun 3

-1

7

65,000

Days 22

Jun 4

0

7

64,000

Days 23

Jun 5

0

7

61,000

Days 24

Jun 6

-2

5

41,000

Days 25

Jun 7

-2

3

24,000

Days 26

Jun 8

-1

2

15,400

Days 27

Jun 9

-1

1

7,400

Days 28

Jun 10

0

1

7,300

Days 29

Jun 11

0

1

7,048

Days 30

Jun 12

0

1

6,736

Days 31

Jun 13

0

1

6,428

Days 32

Jun 14

0

1

6,125

Days 33

Jun 15

0

1

5,708

Days 34

Jun 16

0

1

5,301

Days 35

Jun 17

0

1

4,960

Days 36

Jun 18

0

1

4,571

Days 37

Jun 19

0

1

4,086

Days 38

Jun 20

0

1

3,620

Days 39

Jun 21

0

1

3,270

Days 40

Jun 22

0

1

2,931

Days 41

Jun 23

0

1

2,514

Days 42

Jun 24

0

1

2,119

Days 43

Jun 25

0

1

1,827

Days 44

Jun 26

0

1

1,549

Days 45

Jun 27

0

1

1,360

Days 46

Jun 28

0

1

1,145

Days 47

Jun 29

0

1

1,108

Days 48

Jun 30

3

4

3,317

Days 49

Jul 1

2

6

3,219

Days 50

Jul 2

0

6

2,360

Days 51

Jul 3

0

6

1,408

Days 52

Jul 4

0

6

943

Days 53

Jul 5

0

6

1,275*

Days 54

Jul 6

0

6

1,015*

Days 55

Jul 7

-6

0

720*

**Flow rate reduction - as more bays are opened, the capacity of each bay will decrease due to the elevation of the water in the receiving basin

*Sluice Gates Opened

NOTE: On Day 45 the structure lost hydraulic connection to the Mississippi River. After that the discharge was due to draining the forebay.