Learning To Manage, Not Fight, the Mississippi River
When the floodwaters subside, experts say we should re-evaluate our relationship with the river
When the floodwaters of the swollen Mississippi River subside, experts say it may be a perfect opportunity to re-evaluate our relationship with the river. The opening of the Morganza Spillway in mid-May is not only helping ease the rising river, it is diverting nutrient-rich sediment to Louisiana's rapidly deteriorating wetlands. This might demonstrate how more diversions and working with the river, instead of against it, may be the best way to battle the rising waters in the future.
Experts say a comprehensive plan of river management should include less emphasis on extended levees and more focus on diversions, elevating homes and long-term creative solutions for managing the river.
Using diversions and spillways to divert floodwaters and carry sediment
David Muth, Louisiana state director for NWF, said the construction of levees since the mid-1800s has pinched off many of the river's distributaries. That has not only stopped sediment from building land in Louisiana's wetlands, it has deprived the river of the space it needs to expand. Annual spring flooding is a part of the natural process and with levees preventing water from entering the flood plains it creates bigger floods downstream.
“We need to give the river more room upstream from the delta so that the floods aren't so severe. The levees are like straightjackets, we need to expand the floodplain,” said Muth.
NWF has identified five activities that exacerbate flood damages and risks. They include: poor federal planning and management; wetlands and stream destruction; floodplain development; poor agricultural practices; and failure to curb carbon pollution.
With cities such as New Orleans, Baton Rouge, Natchez and Memphis already built in the river's natural floodplain, tearing down levees is not a viable solution. Hydrologists say that the answer is to now create more “diversions” to let the river expand its banks into other places.
There are currently only two dedicated diversions on the river, the Caernarvon and Davis Pond. While neither of the diversions were originally designed to carry sediment, minor sediment flow combined with the freshwater impact of stimulating plant growth has helped slow the rate of land loss. Most importantly, it gives the rising river waters a place to go.
Spillways such as the Bonnet Carre and the Morganza can also divert water and help protect cities. During very high waters their gates can be opened to intentionally flood open areas of land. While the Bonnet Carre diverts waters into Lake Pontchartrain, the Morganza can funnel up to 600,000 cubic feet/second to the Gulf through the Atchafalaya Basin.
When the Morganza was last opened in 1973, the sediment that flowed through it was credited with creating substantial land near the mouth of the Atchafalaya Delta. This opening may further demonstrate that by harnessing the power of the river, we can not only protect cities from flooding but restore Louisiana's coast.
“We need to have a series of outlets that we can open during big floods. It will not only help protect communities downstream, it will give those basins the life-giving sediment and nutrients they need,” Muth said.
Using 2011 flood as a model for more creative solutions
Clinton Wilson, Ph.D., an associate professor at the Department of Civil and Environmental Engineering at Louisiana State University, advocates building more diversions where they are needed. With biologists anticipating large sediment buildups and land creation at the mouth of the Atchafalaya, this event should provide hard data to sell to the public and legislators the idea of creating more diversions.
“I think there should be some good hard defendable data on the amount of sediment that has been deposited. We can take that, along with our education and outreach, and show people [what is happening],” said Wilson.
In addition to funding, one such hurdle in creating new diversions is finding the space to put them. There are a number of communities between the river and the Gulf, and sending flood waters down some canals would inundate these towns.
Doug Inkley, senior scientist at NWF, said all rivers have natural flood plains and despite hundreds of years of trying to fight the process, Mother Nature still wins. The Missouri, Arkansas, Ohio and Tennessee rivers have all flooded their banks and impacted cities and towns in recent years.
“We’re trying to stop a natural process. We are confining the river to the main river bed. Rather than fight it, management is more appropriate,” said Inkley.
Muth said that while New Orleans and Baton Rouge could be better protected by diverting rising waters through spillways and diversions, smaller communities in its path would have to be made more flood resistant. That could include raising more homes after the current flood, instituting more building codes that would set minimum elevations and creating “ring” levees where needed. Ring levees are smaller earthen barriers that could be built not along the river itself but around flood-prone communities.
“We need to be more creative because flooding is going to increase. We’re also going to get more flooding from the Gulf. You can build a giant levee from Texas to Mississippi and it won’t work,” said Muth.
Among other solutions, NWF recommends that we modernize federal water policy guidelines that would require the Corps to employee natural solutions in managing the Mississippi River. NWF also calls for protecting wetlands and streams from further development and reforming the National Flood Insurance Program (NFIP).