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Posts tagged Morganza Spillway

Sediments in Mississippi Delta After Floods

30.2N 90.1W

May 31st, 2011 Category: Sediments

USA - May 23rd, 2011

Popcorn clouds hang in the skies above the Mississippi River Delta region and New Orleans, USA, forming dotted lines in the air.

In the clear areas, one can observe Lake Pontchartrain, the lower half of which is tan with sediments, and sediments seeping out of the delta arm of the Mississippi River and into the Gulf of Mexico.

This image was taken around the time of the May 2011 Mississippi River floods, which necessitated the second opening in history of the Morganza Spillway, a flood-control structure in Louisiana along the western bank of the Mississippi River.

Diversion of 125,000 cubic feet per second (3,500 m3/s) of water from the Mississippi River to the Atchafalaya Basin was planned during this event, with the structure operating at about 21% of its capacity.

This diversion was deemed necessary to protect levees and prevent major flooding in Baton Rouge and New Orleans, with the tradeoff of creating severe flooding in the Atchafalaya Basin.

By May 18, 2011, a total of 17 gates had been opened by the Corps of Engineers. The Corps estimated the flow rate at 114,000 cu ft/s (3,200 m3/s). However, on May 25, new estimates from the U.S. Geologic Survey (USGS) described a much higher 172,000 cu ft/s (4,900 m3/s), resulting in the closure of 3 bays by May 26, and additional closures by May 29, bringing the total to 11 bays. The new estimate for 11 bays is 120,000 cu ft/s (3,400 m3/s).