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Atchafalaya Swamp, Louisiana, USA – March 10th, 2009

March 10th, 2009 Category: Image of the day, Lakes, Rivers

Louisiana, USA - March 1st, 2009

Louisiana, USA - March 1st, 2009

A series of bays and wetlands along the southern Lousiana coast. The Mississippi River flows down into the Gulf of Mexico, carrying dense tan and brown sediments.

The bays visible at the bottom center, including Vermilion Bay (left), West Cote Blanche Bay (center) and East Cote Blanche Bay (right).

West of these bays are two lakes: White Lake (right) and Grand Lake (left), which appear dark brown with sediments and practically joined together from high water levels.

East of the bays is the Atchafalaya Basin, or Atchafalaya Swamp, the largest swamp in the United States. It is a combination of wetlands and river delta area where the Atchafalaya River and the Gulf of Mexico converge.

The Atchafalaya is unique among basins because it has a growing delta system (notice the two branchlike protrusions in the full image) with nearly stable wetlands.

The Atchafalaya Basin, the surrounding plain of the river, is filled with bayous, bald cypress swamps, and marshes that give way to more brackish conditions and end in the Spartina grass marshes, near and at where it meets the Gulf of Mexico. It is susceptible to heavy flooding, is sparsely inhabited.

The basin is about 20 miles (32 km) in width from east to west and 150 miles (240 km) in length. With 595,000 acres (2,410 km2), it is the USA’s largest swamp wilderness, containing nationally significant expanses of bottomland hardwoods, swamplands, bayous and back-water lakes.

Atchafalaya River and Bays along the Louisiana Coast

December 20th, 2008 Category: Rivers

Atchafalaya River and bays, Louisiana - December 12th, 2008

Atchafalaya River and bays, Louisiana - December 12th, 2008

This ASAR (radar) image allows viewers to see currents in several bays off the coast of Louisiana, USA, west of New Orleans. The flow of water moves southward, pouring out of various streams and rivers, towards the Gulf of Mexico.

The bays visible are, from left to right, Vermilion Bay, West Cote Blanche Bay, East Cote Blanche Bay and Atchafalaya Bay.

The main river visible (top right) is the Atchafalaya River, a distributary of the Mississippi and Red rivers. It is approximately 170 miles (270 km) long.

Formed near Simmesport at the confluence of the Red River with the Mississippi, it meanders south as a channel of the Mississippi, through extensive levees and floodways, past Morgan City, and empties into the Gulf of Mexico in Atchafalaya Bay approximately 15 miles (25 km) south of Morgan City.

The river is now forming a new delta in the bay – the only place on the Louisiana coastline that is gaining ground.

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).