The Bonnet Carré Crevasse was an 1871 breach in the Mississippi River

Mississippi River

The Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...

 levee

Levee

A levee, levée, dike , embankment, floodbank or stopbank is an elongated naturally occurring ridge or artificially constructed fill or wall, which regulates water levels...

s some 15 miles (24.1 km) upriver of New Orleans, Louisiana

New Orleans, Louisiana

New Orleans is a major United States port and the largest city and metropolitan area in the state of Louisiana. The New Orleans metropolitan area has a population of 1,235,650 as of 2009, the 46th largest in the USA. The New Orleans – Metairie – Bogalusa combined statistical area has a population...

 which resulted in substantial flood

Flood

A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...

ing. It was the worst flooding much of New Orleans had experienced since Sauvé's Crevasse

Sauvé's Crevasse

Sauvé's Crevasse was a Mississippi River levee failure that flooded much of New Orleans, Louisiana in 1849.In 1849 the Mississippi reached the highest water level observed in twenty-one years. Some seventeen miles up river from the city of New Orleans in Jefferson Parish lay a plantation belonging...

 in 1849.

Bonnet Carré was an area in St. Charles Parish, Louisiana

St. Charles Parish, Louisiana

St. Charles Parish is a parish located in the U.S. state of Louisiana. The parish seat is Hahnville. In 2010, its population was 52,780. In the eighteenth and nineteenth century, this was part of the German Coast, an area along the Mississippi River settled by numerous German pioneers in the...

. The East Bank river levee collapsed here at high water so dramatically that attempts to quickly staunch the breach were soon abandoned in the face of the huge and powerful flow of water. The flood eventually spread through most of the East Bank of the Parish all the way to Lake Pontchartrain

Lake Pontchartrain

Lake Pontchartrain is a brackish estuary located in southeastern Louisiana. It is the second-largest inland saltwater body of water in the United States, after the Great Salt Lake in Utah, and the largest lake in Louisiana. As an estuary, Pontchartrain is not a true lake.It covers an area of with...

. The river water increased the water level in the lake and in the system connecting Pontchartrain to the Gulf of Mexico

Gulf of Mexico

The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...

, its eventual outlet. Lake Pontchartrain overflowed its banks, with the water spreading into surrounding communities including the Lake and "Back of Town" sections of New Orleans.
The river levee was not restored at Bonnet Carré until 1883.

The area is now the site of the Bonnet Carré Spillway

Bonnet Carré Spillway

The Bonnet Carré Spillway is a flood control operation in the Lower Mississippi Valley. Located in St. Charles Parish, Louisiana - about west of New Orleans - it allows floodwaters from the Mississippi River to flow into Lake Pontchartrain and thence into the Gulf of Mexico...

.