Environmental Impacts

 

OVERVIEW

Since its construction in the late 1950s and early 1960s, the Mississippi River Gulf Outlet (MRGO) has impacted over 600,000 acres of coastal ecosystems surrounding the Greater New Orleans area—completely destroying over 27,000 acres of wetlands. Prior to construction of the MRGO, the coastal wetlands provided economic opportunities, helped clean water, and provided natural storm surge protection to urban communities like the Lower Ninth Ward, New Orleans East, Chalmette, and Arabi.

In 2005, Hurricane Katrina underscored the importance of the impact of the MRGO on wetlands and public safety when storm waves generated in Lake Borgne regenerated in the MRGO channel and destroyed the earthen levees while the surge was still rising. This large scale breach of levees resulted in catastrophic flooding of communities. In 2007, the U.S. Congress singled out the MRGO's role in Katrina's devastation by calling for the U.S. Army Corps of Engineers (the Corps) to close the MRGO and to develop a plan for ecosystem restoration. The Corps has closed the channel to navigation, which is the first step toward restoring historical salinity levels and reducing erosion along the banks of the MRGO. However, the Corps is still working on a plan to fix the damage caused by the construction and operation of the channel. Much more remains to be done to address this legacy— "Mister Go" isn't gone yet!

 

THE ECONOMIC AND ENVIRONMENTAL COSTS

Wetland destruction caused by the MRGO The Mississippi River Gulf Outlet (MRGO; commonly pronounced "Mister Go") is a 76-mile long artificial channel that was built to provide a navigation shortcut from the Gulf of Mexico to the heart of New Orleans. Authorized by Congress in 1956 and completed by the U.S. Army Corps of Engineers (the Corps) in 1968, the MRGO originally was 650 feet wide at the top and at least 36 feet deep.i More earth was dredged to construct the MRGO than was moved to construct the Panama Canal.ii

Proposed as an economic development project, the MRGO was lightly used and expensive to maintain. In 2006, the MRGO cost taxpayers nearly $20,000 for each vessel traveling in the channel.iii

The MRGO also came at a steep environmental price, which scientists and communities along the MRGO had anticipated before the Corps started construction. When the Corps dredged the channel, they converted 20,000 acres (31.2 square miles) of wetlands to open water, and allowed saltwater to flow inland from the Gulf, eventually damaging an additional 7,600 acres (11.8 square miles) of wetland and lagoon habitat. By 2005, erosion along the channel's banks expanded the MRGO to a width of 3,000 feet in some areas, bringing it in close proximity to the hurricane protection levee. Saltwater moving up the channel also damaged or destroyed freshwater cypress forests of Orleans and St. Bernard Parishes, and created a dead zone in Lake Pontchartrain. All told, the construction and operation of the channel has impacted more than 618,000 acres (965.6 square miles) of habitat—an area almost three times the size of New York City's five boroughs.

 

THE HUMAN COST

A home in the Lower 9th Ward - Post Katrina When communities like the Lower Ninth Ward, Arabi, and Chalmette were established, a natural storm buffer of cypress trees and other wetlands helped protect them from hurricanes. The MRGO put those communities at risk by damaging or destroying that protective buffer.

Despite being at a higher elevation than much of New Orleans, St. Bernard Parish and the Lower Ninth Ward (called "Lower" because it is downriver from the Upper Ninth Ward) experienced the deepest, most violent flooding in the New Orleans metro area during Hurricane Katrina. According to a 2009 report by eight expert scientists, the extensive flooding in this area was directly attributable to the MRGO. Through detailed wave and hydrodynamic modeling, the scientists showed that waves in Lake Borgne were able to rebuild to 8 to 9 feet high as they crossed the MRGO channel, breaching the earthen levees along the channel while the surge was still rising. The flooding was also worsened by the levee-lined intersection of the MRGO and the Gulf Intracoastal Waterway, which funneled storm surge through the MRGO and into the Industrial Canal—flooding the heart of the city. During Hurricane Katrina, the fierce surge and waves caused levees and flood walls to collapse and unleashed a wall of water into densely populated communities east of the Industrial Canal.

It is clear that MRGO destroyed communities and cost lives. Restoring natural storm surge protection must be a major focus in planning the restoration of areas affected by the MRGO.

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