Human intervention halted the natural land building process of the Mississippi Delta.
Since the mid-eighteenth century, residents of New Orleans and other river settlements in the delta built levees to protect themselves from flooding.The flood of 1927, at the time the largest and most disastrous in the history of the Lower Mississippi Valley, prompted interventions including the construction of improved levees, spillways and dams as well as associated flood and additional navigation management structures designed to contain overflows and manage and stabilize a deepwater channel.
Containing the river starved adjacent wetlands of the fresh water and sediment needed to stave of the Gulf of Mexico’s rising tides. The delta has grown so far into the Gulf the River’s mouth is at the edge of the continental shelf. As a result, the 120 million tons of sediment the River carries ends up in deep water, where it is lost forever.The situation has been exacerbated by regional subsidence (sinking of the land) associated with man-made and natural forces, and compounded further by sea level rise and the increased volatility and severity of weather events resulting from global climate change.
The resulting land loss across the delta is leading toward catastrophic collapse. Over the last century, almost 1,900 square miles of deltaic wetlands, an area approximately the size of Delaware, have disappeared from Louisiana. Without action, by 2100 Louisiana won’t have any wetlands at all.
Maintaining the shipping channel and flood protection for coastal communities has led to increasingly expensive challenges. The necessity of safeguarding existing commerce and navigation has led to increasing levels of river management to protect the existing channel alignment and depth. Simultaneously, communities flourished in the protected areas behind the levees, increasing the need for protection and driving expectations of further flood-risk reduction. The unpredictability of congressionally approved funding for projects carried out by the U.S. Army Corps of Engineers exacerbates the problem.