Louisiana's Flood History: At a glance

The beautiful state of Louisiana has a total square mile count of 51,843. 8,277 square miles of that total are bordering water, this includes many lagoons, rivers, bayous and lakes. Louisiana’s main waterway, the Mississippi River has a habit of flooding and then draining into the Gulf of Mexico, the water commonly flows through the heart of the Mississippi Delta. This area is approximately just 100 miles southeast of the city of New Orleans.

As a whole, Louisiana is made up of plains divided into three geographic sections: the East Gulf Coastal Plain, the Mississippi Alluvial Plain, and the West Gulf Coastal Plain. This means that much of Louisiana lies at close to sea level making damage from flood events a very real possibility. In fact, the highest point in the state, Driskill Mountain which sits close to the Arkansas border, is a mere 535 feet above sea level. Some areas actually sit below sea level; the lowest point of the state - 8 feet below sea level - is in New Orleans.

The Plains

East Gulf Coastal Plain - this marshland plain encompasses the area north of Lake Pontchartrain and east of the Mississippi River. Most of the area is lowlands, but rises to rolling hills in the northern-most part.

Mississippi Alluvial Plain - the most bountiful plain of the three, the Mississippi Alluvial Plain runs adjacent to the Mississippi River from Arkansas down to the Gulf of Mexico and is distinguished by hollows and ridges. Much of the soil is made up of silt and clay. The fertile Mississippi Delta is part of this plain.

West Gulf Coastal Plain - To the west of the Mississippi Alluvial Plain is the West Gulf Coastal Plain which consists of barrier beaches along the Gulf of Mexico, marshland that extends nearly 20 miles inland, and the Louisiana Prairies the furthest north. Driskill Mountain is part of this plain.

River Flooding

1927 - The Great Mississippi Flood

Described by Herbert Hoover, then the U.S. Secretary of Commerce, as "the greatest peace-time calamity in the history of the country," the Great Mississippi Flood of 1927 impacted over 16 million acres in seven states including Kansas, Oklahoma, Illinois, and Louisiana. Caused by excessive rainfall that ran from the summer months of 1926 all the way through the spring of 1927, the flood caused significant devastation along the river's route. In total, more than 245,000 homes and businesses were damaged by flood waters, the death toll ranged from 250 to 500, and the damaged reached well beyond $400 million dollars.

In Louisiana, a total of 10,000 square miles spread over 20 parishes lay submerged beneath flood waters. New Orleans, itself, saw 11.16 inches of February rainfall, a far cry above the normal average of 4.4 inches. The rainfall was unceasing through March and the first half of April. On the 15th - Good Friday, as it turned out - in excess of 14 inches deluged the city and overwhelmed the city's drainage pumps.

At this point, none of the levees were breached, but neither did they let the water in the city drain which essentially put pressure on the levees from both sides since the Mississippi River was also steadily rising. This prompted residents of the Crescent City to buy boats and start stockpiling food.

With the levees in such a precarious position, a decision had to be made to either do nothing and risk New Orleans flooding from a levee break upstream or manually breach a levee downstream to drain the city. Governor O.H. Simpson opted to manually breach a downstream levee to create an alternate route to the Gulf of Mexico. On April 29, destruction of a levee at Caernarvon, a city just shy of 20 miles southeast of New Orleans, began. 10 days later, a waterway was created which routed excess water from the Mississippi River.

This course of action had far-reaching consequences. 10,000 residents of the area that would be flooded once the waterway was opened had to be evacuated, the vast majority of whom lost everything. To add insult to injury, the manual destruction of the levee proved to be unnecessary since the levees eventually experienced a breach on their own which helped remove pressure on the New Orleans levees. Areas to the south were not in the clear yet as was seen when levees on the Atchafalaya River and at Bayou des Glaises were breached. The water that poured through these breaches merged north of St. Landry Parish's Port Barre. Arnaudville, Beaux Bridge, St. Martinville, New Iberia, Jeanerette, Franklin, and Morgan City were all inundated with flood waters.

The month of May closed with 60,000 refugees, thousands of drowned cattle, and acres of farm crops lost as southern Louisiana was formed into a lake that spanned between 50 and 100 miles wide and 200 miles long. The flood waters didn't begin to empty into the Gulf of Mexico until June.

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1973 - Lower Mississippi Flood - March - May

Not since the Great Mississippi River Flood of 1927 had such a large volume of water flowed down the Mississippi River. The Bonnet Carre Spillway was opened from April 7th through June 14th to release the excess water into Lake Pontchartrain. The Morganza Spillway was also utilized for the first time from April 19th through June 13th which diverted water from the Mississippi to the Atchafalaya Basin and into the Atchafalaya River.

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1983 - Lower Mississippi Flood

The lower Mississippi Flood in May and June of 1983 ranks second for the most destructive flood since 1927. Red River Landing in Pointe Coupee Parish sustained flooding lasting 115 days. The Bonnet Carre Spillway in St. Charles Parish was opened for 35 days to let water drain into Lake Pontchartrain and further into the Gulf of Mexico. Many flood stage records were set: On May 29th, the river crested at 33.30 feet in Donaldsonville, on May 31st, it reached 43.90 at Baton Rouge. Damages were estimated at $15.7 million.

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2011 - Great Mississippi Flood of 2011

The April and May floods of the Mississippi River began with two large storms that dropped record-breaking levels of rain on the Mississippi River watershed which stretches from the Allegheny Mountains westward to the Rockies and includes 31 states, either in total or in part, and 2 provinces in Canada. When this rain mixed with the annual spring snowmelt, record river levels were experienced from as far north as Illinois and Missouri all the way down to Louisiana. Thousands were evacuated out of concern for historic flood possibilities and for the first time since the 1973 flood, the Morganza Spillway was opened to divert the excess river water. This saved most of Baton Rouge and New Orleans from being inundated, though it did purposefully flood 4,600 square miles of the Louisiana countryside in order to do so.

The Bonnet Carre Spillway was also utilized to reduce water levels near New Orleans and to help maintain the integrity of the levees that safeguard the city. They were opened on May 23rd and fully closed by June 20th.

Hurricanes

1893 - Chenier Caminada Hurricane

October 1893's Chenier Caminada Hurricane was the most deadly in Louisiana history. Nearly 500 coastline miles from Timbalier Bay in southeastern Louisiana to Pensacola, Florida were devastated. The hurricane made landfall between New Orleans and Port Eads on October 1st, with the area from Bayou Lafourche to the Balize bearing the brunt of the devastation. New Orleans flooded and major damage was sustained in Neptuen, Ostrica, Point Pleasant, and Doullut. Buras in Plaquemines Parish suffered near total devastation with only two homes left standing. Plaquemines Parish also lost about 60% of its orange crop.

The number of deaths ranged anywhere from 1,848 to 2,448, with the tally finally stabilizing at 2,000. The estimated cost of damages reached in excess of $21,000, an astronomical amount at the time.

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1915 - Unnamed New Orleans Hurricane

In 1915, an unnamed, Category 4 hurricane smashed into New Orleans making landfall near Grand Isle. The results were devastating. Many homes and buildings were damaged or destroyed completely, including the collapse of two churches - a Presbyterian Church in Lafayette Square and Anna's Episcopal Church on Esplanade Avenue. Audubon Park saw its Horticultural Hall destroyed. It was reported that Lake Pontchartrain waters forced themselves into the drainage canals, flooding New Orleans. This was also seen with Hurricane Katrina in 2005. The Mid-City neighborhood experienced substantial flooding after the electrical power to the drainage pumps failed. St. Bernard Parish, the Rigolets, and the area around Lake Catherine were impacted by a 13-foot storm surge. The death toll reached 275, and the estimated damages reached $13 million.

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1957 - Hurricane Audrey

On June 27th, southwest Louisiana saw its most devastating hurricane in the form of Hurricane Audrey bringing with it storm surges up to 12.4 feet and causing waves that reached as high as 20 feet. The storm surges and river flooding inundated over 1.6 million acres. Cameron bore the brunt of the storm; many residents had taken shelter in the courthouse which was the only building to survive. Many of the area's wood houses were lifted and carried off by the flood waters, some landing miles away from where they originally stood.

Animals did not fare well, either. Portions of the Menard Intracoastal Canal were obstructed by the carcasses of alligators, cattle, muskrats, nutria, and snakes. In terms of human lives, 416 people were killed, most from Cameron Parish. The damages were estimated at $120 million.

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2005 - Hurricane Katrina

Hurricane Katrina made landfall near Buras-Triumph, Louisiana, on August 29, as a strong Category 3 hurricane, unleashing massive devastation. Between 8 and 15 inches of rain fell, with the area near Slidell receiving the highest amount recorded. All of the parishes surrounding Lake Pontchartrain were inundated by storm surges, some reaching up to 16 feet. As a result, Lake Pontchartrain overflowed and areas between Slidell and Mandeville were flooded. 217 square miles of coastal wetlands were also decimated. The total cost to all impacted areas of the United States is estimated at $108 billion. The total number of deaths reached 1,836, with 135 unaccounted for. 1,577 of those deaths happened in Louisiana.

Buildings and homes suffered extensive damage. According to the Department of Housing and Urban Development (HUD), 70% of homes in St. Tammany Parish were damaged, 80% in Plaquemines Parish, and 81% in St. Bernard Parish. New Orleans didn't fare much better. Some of the city's residents had evacuated, but many of those who remained found themselves huddled in the Superdome which had been set up as a shelter to ride out the storm and which ultimately suffered severe damage, as well, when the roof and waterproofing failed.

The failure of the levee system was perhaps the most devastating. Levees in St. Bernard Parish were breached, as were 53 levees protecting New Orleans, allowing flood waters to engulf the area. The vast majority of the main roads leading in and out of New Orleans were damaged, leaving only two ways in and out of the city - The Crescent City Connection and the Huey P. Long Bridge. It was the levee breaches, as well, that caused a significant portion of the deaths. Over 700 victims were discovered in New Orleans alone, with many having been found along city streets or floating on flood water. The levee failures rank at the top of the United States' most devastating civil engineering disasters.

The environmental impact from Katrina was immense. 30 oil rigs were destroyed completely or damaged, with oil spills seen at 44 southeastern Louisiana facilities. Most of the spills were contained before they could reach beyond the sites of their leaks, but even still, a mix of water and oil flooded Meraux. In total, over 7 million gallons of oil were spilled. 9 refineries were also closed due to Katrina.

It wasn't just oil that was found in the flood waters. In New Orleans, excess water was pumped back into Lake Pontchartrain over the course of 43 days. It was discovered that the water contained a combination of bacteria, heavy metals, oil, pesticides, raw sewage, and toxic chemicals.

With the majority of Louisiana sitting near sea level and its history of flood-events, flood insurance coverage is as important now as it ever has been. More information concerning flood insurance can be found on the pages of our website. For information concerning natural disaster preparation in the state of Louisiana, please visit The Governor's Office of Homeland Security & Emergency Preparedness.