The 1871 Bonnet Carré Crevasse breached a Mississippi River levee 31 miles from New Orleans, flooding populated areas and prompting construction of an artificial spillway.
Key Facts
- Distance from New Orleans
- 31 miles (50 km)
- Original levee height
- Over 12 feet (3.7 m)
- Breach width
- Approximately 1,200 feet (370 m)
- Floodwater speed
- 8 miles per hour
- Levee restored
- 1883
By the Numbers
Location
Cause → Event → Consequence
Excess water from the Mississippi River overtopped the east bank levee at Bonnet Carré, a point approximately 31 miles from New Orleans. The original levee stood over 12 feet high but could not contain the rising river. Local drainage infrastructure was insufficient to manage the resulting overflow, and strong northerly winds worsened the situation by pushing floodwaters toward inhabited areas.
The east bank levee at Bonnet Carré failed, opening a crevasse roughly 1,200 feet wide through which water rushed at 8 miles per hour. The breach widened daily as floodwaters inundated local areas and entered Lake Pontchartrain. A secondary nearby levee also broke under the increasing hydraulic pressure, extending the flood's reach into neighborhoods including Metairie and Gentilly.
Despite significant devastation, the crevasse had ecological benefits by diverting river sediment and reducing broader land erosion in surrounding wetlands. Recognizing this, local authorities commissioned an artificial crevasse to periodically relieve Mississippi flood pressure into Lake Pontchartrain. The original levee was not repaired until 1883, and the site eventually became the location of the Bonnet Carré Spillway.