Flood control along the Mississippi River is a central piece of a newly passed federal law — work that advocates believe is critical as the river basin sees more frequent and severe extreme weather events due to climate change. 

The Water Resources Development Act (WRDA) is passed by Congress every two years. It gives authority to the U.S. Army Corps of Engineers to undertake projects and studies to improve the nation’s water resources. 

Signed into law Jan. 4, this year’s package includes studies on increased flooding in the upper basin, flood mitigation measures throughout the river system, ecological restoration, and a $6 billion floodwall in Louisiana. 

The Mississippi River is managed in large part by the Corps of Engineers, so it often features prominently in the bill, with a dual aim of making the river more suitable for shipping and restoring environmental degradation from flooding, nutrient pollution and climate change. 

Kirsten Wallace, executive director of the Upper Mississippi River Basin Association, called this year’s WRDA “a pretty special one.” She said it contained wins for many of the diverse stakeholders along the river, including shippers, environmental advocates, riverfront communities and federal and state agencies — who don’t always agree. 

Advocates lauded the law’s emphasis on nature-based solutions. In a press release, Stephanie Bailenson, policy team lead for The Nature Conservancy, said, “Since 2016, Congress has directed the Corps to consider natural and nature-based solutions alongside or instead of traditional infrastructure. This latest act continues that trend.”

But all of these projects are only promised, because funding doesn’t come until later, when Congress appropriates it. Many projects authorized in previous versions of the law are still unfunded, according to the Congressional Research Service.

Here’s what will affect the river in the Water Resources Development Act of 2024: 

Flood risk study

The law authorizes a large-scale study of flooding on the Upper Mississippi River System, which includes the Mississippi River from its headwaters to where it meets the Ohio River at Cairo, Illinois, as well as the Illinois River and portions of some smaller tributaries.

The upper river has seen two major floods in the last few years; one in 2022, and one in 2019, which lasted for months and caused billions of dollars in damage. 

The study’s chief goal: figuring out how to reduce flood risk across the entire river system, instead of relying on municipalities to try to solve flooding problems themselves, which can sometimes have impacts downstream. North of St. Louis, for example, levees constrain the river to protect communities and valuable farmland from flooding — and some levee districts have raised those levees higher, safeguarding themselves but effectively pushing floodwaters faster downstream. 

“This plan allows more of a comprehensive way for levee districts to improve what they currently have … in a way that doesn’t put them in a position to be adversarial or just impose risk somewhere else,” Wallace said. 

She said the study will be a challenge, but that levee districts are eager for solutions as flood risks and heavier rainfall increase. 

Once the study receives funding, it will be led by the Army Corps’ St. Louis District, Wallace said. It’ll solicit input from cities, towns and ports along the river, recreators, the shipping industry and federal environmental agencies like the U.S. Fish and Wildlife Service and the U.S. Geological Survey. 

Flood projects

Cities and towns along the river could get help for the localized effects of flooding too, thanks to several projects authorized by the law. Upstream, that includes La Crosse, Wisconsin, which will enter into an agreement with the Army Corps to study the role of the city’s levees, which were constructed around the river’s record flood in 1965. 

“We have to have an eye on maintaining what we’ve got and looking toward the future and whatever conditions the river might undergo to be prepared as best we can,” said Matthew Gallager, the city’s director of engineering and public works. “Because obviously, nature is going to win.” 

Downriver, Louisiana secured the largest project authorization within the law. To protect communities in St. Tammany Parish, north of Lake Pontchartrain, Louisiana plans to build a $5.9 billion levee and floodwall system totaling 18.5 miles in length to protect over 26,000 structures, most of which are family homes. 

The St. Tammany Flood Risk Management Project is slated to receive $3.7 billion in federal funding. The other 35% will come from non-federal sponsors, such as the Louisiana Coastal Protection and Restoration Authority (CPRA). 

“By authorizing the St. Tammany project for construction, Congress recognizes again the national importance of Louisiana and that CPRA can work with the Federal Government to execute a multi-billion coastal protection project successfully,” CPRA Chairman Gordy Dove said.

The law also authorizes a federal study of the Lake Pontchartrain Storm Surge Reduction Project, a component of Louisiana’s Coastal Master Plan meant to protect nine parishes bordering the lake. The Army Corps of Engineers will investigate whether the proposed project to reduce flood risk is in the federal interest. 

Other approved flood control projects will be funded along the lower Mississippi River and its tributaries, including the Ouachita River in Louisiana. Several counties in Mississippi will also receive funding to improve environmental infrastructure, such as water and wastewater systems. 

Near Memphis, the bill authorizes the Hatchie-Loosahatchie Ecosystem Restoration project, which covers a 39-mile stretch of the lower Mississippi River. The project aims to manage flood risks while also restoring and sustaining the health, productivity and biological diversity of the flyway. 

In New Orleans, a study was authorized to investigate ecosystem restoration and water supply issues, such as the mitigation of future saltwater wedges that threaten drinking water and wetlands at the very end of the Mississippi River. 

Upper Mississippi River restoration

The law also increases the amount of money Congress can give to the Upper Mississippi River Restoration program, which funds habitat restoration activities and scientific research on the upper river. 

Congress increased the money it can direct to the research part of the program by $10 million, bringing the total the program can get to $100 million annually. 

The boost “really is a recognition of the value of the science … the understanding that has improved about how the system is functioning over the last three decades,” said Marshall Plumley, the Army Corps’ regional manager for the program. 

If given extra funding, Plumley said program staff want to use it to better understand the effects of the increased amount of water that has flowed through the river in recent years. That increase, partly attributed to wetter conditions due to climate change, is changing the river’s floodplain habitats, including forests and backwater areas. 

Water infrastructure funding

The Mississippi River functions as a water superhighway, transporting around $500 million tons of goods each year. Infrastructure to keep shipping running smoothly is costly, and one adjustment in WRDA 2024 is aimed at shifting the burden of those costs. 

Taxpayers have been funding inland waterway infrastructure for nearly two centuries, but Congress established the Inland Waterways Trust Fund in 1978, which requires the private shipping industry to pitch in. 

Today, the trust fund’s coffers are filled by a 29-cent per gallon diesel tax on commercial operators that use the Mississippi River and other inland waterways, adding up to about $125 million per year in recent years. New construction — like wider, more modern locks and dams on the upper river — is paid for through a public-private partnership: the private dollars in the fund, and federal dollars allocated by Congress. 

Until recently, the private dollars covered 35% of new construction costs and federal dollars covered 65%. The new WRDA adjusts that to 25% and 75%, respectively. 

Advocates for the shipping industry have long believed taxpayers should have a bigger hand in funding construction because it’s not just shippers who benefit from an efficient river. 

The balance in the trust fund “always limits” construction that can happen in a given year, said Jen Armstrong, director of government relations for the Waterways Council. 

“We can’t afford to have projects take three decades or two decades to complete,” Armstrong said, “because we have other locks that are deteriorating.” 

Armstrong said she believes shifting more of the cost to the federal government will accelerate those projects. 

Not everyone supports the cost share change, however, including American Rivers, which has opposed the creation of new locks on the upper Mississippi in favor of helping the river revert to more natural processes. 

Kelsey Cruickshank, the group’s director of policy and government relations, called it “a disappointing development that continues to give short shrift to the incredible ecosystem of the world’s third-largest freshwater river system.” 

This story is a product of the Mississippi River Basin Ag & Water Desk, an independent reporting network based at the University of Missouri in partnership with Report for America, with major funding from the Walton Family Foundation. The Nature Conservancy and American Rivers also receive Walton funding.