Atchafalaya Basin

The Atchafalaya is a distributary of the Mississippi and it is shorter and steeper to the Gulf, which means the river has been trying to switch into it for decades - the Old River Control Structure upstream exists to prevent that, and it nearly failed in the 1973 flood. If it goes, the Mississippi changes course and Baton Rouge and New Orleans lose their river. The basin below covers around five and a half thousand square kilometres of bottomland hardwood, cypress-tupelo swamp and bayou, the largest swamp in the United States, with some 110,000 hectares of cypress forest, the largest remaining tract of coastal cypress in the country, and the Louisiana black bear in its woods. Crawfish, alligators and a very long bird list live in it. Boat tours run from Henderson, and I-10 crosses it on a bridge about thirty kilometres long.

What's there

• Cypress-tupelo swamp - the largest river swamp in the country.
• A river trying to change course - held by the control structure upstream.
• A thirty-kilometre bridge - carrying I-10 across the basin.
• Alligators, crawfish and wading birds - through the bayous.

When to go

October to April; summer heat and mosquitoes are severe. A full day.

Practical notes

Access is by boat - the swamp is not walkable. Tours vary considerably in quality. Summer is punishing. Water levels change what is reachable.

Nearby

Breaux Bridge is west; Baton Rouge is east.

Key facts