Ironically, Flood Control is Flooding New Orleans

Katrina floodwaters. Photo courtesy of ABC News

Man-made flood-control systems—such as levees, upstream dams, and canals—continue to be responsible for widespread damage to the New Orleans and Louisiana landscapes.

The levees and canals on the Mississippi River provide infrastructure for oil excavation, shipping, and land development, yet they are the primary culprits in the degradation of natural wetlands. Many other ecosystems changes, such as deforestation, species invasion, and land cultivation, have also contributed to wetland loss in the region.

Wetlands act as natural speed bumps for severe weather. Storm waters lose energy as they pass over swamps, marshes, or mangrove forests, which helps reduce flooding. One study found that two to four miles of wetlands lessen a storm surge height by up to 12 inches.

Unfortunately, the coastal wetlands that provide this protection are disappearing rapidly. Louisiana has been losing up to 40 square miles of marsh per year for several decades. In other words, a football-field-sized segment of wetland disappears into open water every 30 minutes. The open sea has advanced some 20 miles inland due to wetland degeneration.

In its natural state, the Mississippi River periodically changed course within a 200-mile wide arc known as the Mississippi Delta. The delta forms as the river deposits silt over time, creating land mass and wetlands. Historically, this counteracted the natural subsidence that occurred in the region by flooding low lying areas and replacing the soil that was lost. In contrast, levees confine the Mississippi River to one path. As a result, the Mississippi is depositing its silt deep into the Gulf of Mexico and the Delta is sinking. Additional sinking results from underground oil, gas, and water extraction.

The impact of human activity in southern Louisiana became painfully clear when Hurricane Katrina hit in August 2005. Ecosystem degradation, and in particular the loss of wetlands and the shoreline protection ecosystem services they provide, contributed to the devastating scale of the disaster. Eighty percent of New Orleans flooded, power was out across four states for several weeks, over 1,000 people drowned, and levels of pollution were extreme. The economic damage of Katrina has been estimated to be in the range of $200 billion.

To quote Albert Einstein, “the significant problems we face cannot be solved with the same level of thinking used when we created them.” The State of Louisiana has estimated that economic losses from public-use and infrastructure would be $137 billion over 50 years if wetland loss were to continue unchecked. It is expensive to recreate the storm and flood protection services of wetlands once they are lost, yet maintaining and protecting them continues to be ignored. To date, the U.S. Army Corps of Engineers has used most of its allocated $7 billion reconstruction budget for traditional engineering projects.

WRI has a new report, Ecosystem Services: A Guide for Decision Makers, which will help people avoid the inadvertent loss of ecosystem services and connect nature’s health to the achievement of social and economic goals.