Climate change forcings are having significant impacts in coastal Louisiana today and increasingly affect the future of New Orleans, a deltaic city mostly below sea level, which depends on levee and pumps to protect from a host of water-related threats. Precipitation has increased in the Mississippi River basin generally, increasing runoff, so that in recent years the Mississippi River has been above flood stage for longer periods of time both earlier and later in the year, increasing the likelihood that hurricane surge, traditionally confined to summer and fall, may compound effects of prolonged high water on river levees. The Bonnet Carré Spillway, just upstream of New Orleans has been operated more often and for longer periods of time in recent years than ever before in its nearly 100-year history. Because all rain that falls within the city must be pumped out, residents have been exposed to interior flooding more frequently as high-intensity precipitation events can occur in any season. A sustainable path for New Orleans should involve elevating people and sensitive infrastructure above flood levels, raising some land levels, and creating water storage areas within the city. Management of the lower Mississippi River in the future must include consideration that the river will exceed its design capacity on a regular basis. The river must also be used to restore coastal wetlands through the use of diversions, which will also relieve pressure on levees.
High Water: Prolonged Flooding on the Deltaic Mississippi River