Atchafalaya Basin

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The Atchafalaya Basin, or Atchafalaya Swamp, is the largest wetland and swamp in the United States. Located in south central Louisiana, it is a combination of wetlands and river delta area where the Atchafalaya River and the Gulf of Mexico converge.

The river stretches from near Simmesport in the north through parts of eight parishes to the Morgan City area in the south.

The Atchafalaya is unique among Louisiana basins because it has a growing delta system with nearly stable wetlands. The basin contains about 70% forest habitat and about 30% marsh and open water.

It contains the largest contiguous block of forested wetlands remaining (about 35%) in the lower Mississippi River valley and the largest block of floodplain forest in the United States. Best known for its iconic cypress-tupelo swamps, at 260,000 acres (110,000 ha), this block of forest represents the largest remaining contiguous tract of coastal cypress in the US.

The Basin, which is susceptible to long periods of deep 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. The Basin is the largest existing wetland in the United States with an area of 1,400,000 acres (5,700 km2) including the surrounding swamps outside of the levees that historically were connected to the Basin.