Historically, the Mississippi River has been prone to overflowing its banks and flooding nearby cities and states. After the Great Flood of 1927, the U.S. Army Corp of Engineers was tasked with building levees and spillways in an attempt to control and mitigate the destructive effects of the flooding. By 1931, the Bonnet Carre Spillway was completed to divert excess water into nearby Lake Pontchartrain and the Mississippi Sound. The spillway has 350 gated bays that can be opened or closed by cranes operating on the 1.5-mile weir crossing the floodway. Since the end of its construction, the spillway has been opened 14 times, most recently in 2019.
Beginning in February 2019, the U.S. Army Corps of Engineers opened Louisiana’s Bonnet Carre Spillway twice for a total of 123 days in order to prevent flooding in low-lying New Orleans. Before that, the record was held by the 75-day opening in April 1973. While New Orleans and the rest of Louisiana were spared, these long 2019 openings had terrible effects on the state of Mississippi. When the spillway began diverting to Lake Pontchartrain and the Mississippi Sound, the millions of gallons of water flowing into Lake Pontchartrain soon spilled over into the Sound. But it wasn’t just water that flooded into the Sound, it was also fertilizer and sediment, which became catalysts for disaster.
By the time the spillway closed in August 2019, there had already been a disastrous domino effect on Mississippi’s economic and environmental state. Since the Mississippi Sound is a saltwater body, the freshwater intrusion disrupted the balance of the environment. The fertilizer runoff further exacerbated this issue and caused blue-green algae blooms, which are a highly toxic health hazard. According to the New York State Department of Health, “Exposure to high levels of blue-green algae and their toxins can cause diarrhea, nausea or vomiting; skin, eye, or throat irritation; and allergic reactions or breathing difficulties.” Additionally, drinking any water contaminated by blue-green algae may cause liver problems in both humans and animals. Because of the environmental disruption, Mississippi’s seafood crops took massive hits. In September 2019, the Department of Marine Resources estimated 95% of the oyster population had died from too low of a salinity level, which ended oyster harvests for the rest of the year. Additionally, the shrimp harvest decreased by 85% and the crab harvest dropped by 35-40%. This is incredibly economically devastating, especially since Mississippi is reportedly America’s poorest state. But perhaps worst of all was the fact that Mississippi was not alerted by the Army Corps of Engineers about the spillway openings.
In December 2019, the state of Mississippi filed a federal civil lawsuit against the Army Corps of Engineers because of the “unprecedented devastation upon the Mississippi Sound,” finally making years-long tensions public. In the months that have followed, some have argued that a flood control plan from the 1920s is outdated and doesn’t accommodate the needs of 21st century environments. Others argued that the Corps of Engineers were stuck in a no-win situation and had no other choice but to open the Bonnet Carre. Fortunately, officials from both Mississippi and the Army Corps of Engineers will be meeting in June 2020 to try and work out better solutions for the future. But ultimately, the 1928 Flood Control Act by which the Corps operates will have to be changed to lessen future negative impacts on Mississippi’s environment.