Mississippi River Flooding: Morganza Floodway to open Saturday

From a source of life to … in 150 years

Engineers to open key floodway to avert flooding in Baton Rouge and New Orleans

Louisiana state officials have confirmed that the Army Engineers would open the Morganza Spillway by early Saturday evening (CDT), a report said.

The move is intended to avert flooding in Louisiana’s two largest cities, Baton Rouge and New Orleans; however, it could inundate  many thousands of homes and large tracts of crops.

Flooding in Atchafalaya basin is expected to exceed20 feet, affecting about 25,000 people, more than 10,000 buildings and up to 20,000 acres of cropland.

Mississippi River

The largest river in North America, the Mississippi River flows 2,340 mi (3,765 km) from its source at Lake Itasca in the Minnesota North Woods, through the midcontinental United States, the Gulf of Mexico Coastal Plain, and the Louisiana Delta. “’Mississippi’ is an Ojibwa (Chippewa) word meaning great river or gathering of waters—an appropriate name because the river basin, or watershed, extends from the Allegheny Mountains in the eastern United States to the Rocky Mountains, including all or parts of 31 states and 2 Canadian provinces. The river basin measures 1.85 million mi² (4.76 million km²), covering about 40 percent of the United States and about one-eighth of North America.” Mississippi River has the world’s third largest watershed area and seventh average discharge rate. Source: USGS

Morganza Spillway – Satellite Images

Flooded Morganza Spillway.  May5, 1973. Click image to enlarge. Download largest image (2 MB, JPEG)

False color images using near-infrared, red, and green wavelengths. The top image taken by Landsat 1;  bottom image from Landsat 2.  Source: NASA-EO

Morganza Spillway area Sans flooding, 1977. Click image to enlarge. Download largest image (2 MB, JPEG)

Atchafalaya River is forecast to  crest at between 12 and 13 feet at Morgan City on May 23,  if the floodway is opened, breaking a previous record crest  10.6 feet, which was in 1973, a report said.

“They’ve still not officially made a decision on whether or when they will open the spillway, but the Corps of Engineers did tell me today that there are at 1.423 million cubic feet per second at Red River Landing and they are likely to get to 1.5 (million cubic feet) by [Saturday] evening and they will operate that system so that they will not allow that flow to exceed 1.5 through the Baton Rouge area,” Jindal said.

“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 cubic feet per second and rising, the Corps considers opening the Morganza Floodway.” The Army Corps said.  The Army Engineers said the flow rates were 1.449 million cubic feet per second at 7:00am CDT on Friday, May 13, 2011.

Mississippi River Commission Map

Click images to enlarge.

Lower Mississippi Valley Division and  Mississippi River Commission Map

Mississippi River Floodways

 Morganza Floodway

Morganza floodway as a substitute for the East Atchafalaya floodway that was originally planned for in the 1928 Flood Control Act. Governed by a 3,900-foot long and a 125-bay intake structure, the floodway is designed to divert 600,000 cfs from the Mississippi River during the project design flood. The Morganza floodway is operated when the Mississippi River flows below Morganza are projected to exceed 1,500,000 cfs, thereby assuring that flows between Morganza and Bonnet Carré remain at or below 1,500,000 cfs. The Morganza floodway, completed in 1953, has only been operated during the 1973 flood. Source: The MR & T Flooways Project – Mississippi River Commission 1973 .

Estimated Cost of Damage: $5billion [FIRE-EARTH estimate, as of posting]

Related Links

• Mississippi River breaks flood record at Natchez Posted on May 12, 2011

• More Severe Thunderstorms, Rain and Flash Flooding
• Flooding in Memphis – Update May 10
• Mississippi River Flooding: Disaster in Slow Motion
• Epic Flooding Could Inundate Large Parts of the U-S  Posted on February 10, 2011
• The Day Before Washington’s Birthday   Posted on February 20, 2011

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• 2011 Disaster Calendar