The USACE St. Louis District recognizes the value of creating sustainable projects that integrate multiple missions by working with nature. Through the trust developed by years of collaboration with a wide range of project partners representing diverse missions, the District has a history of developing and implementing solutions that support USACE missions while increasing environmental and social value.
Engineering with Nature to Maintain Navigation on the Upper Mississippi River
The Corps of Engineers has been engineering the Mississippi River dating back to the early 19th Century. The objectives of the early projects were simple; to do whatever was necessary to get the required navigation dimensions and direct the river where we wanted it. This included the construction of long river training structures, the closing of side channels, snag removal, and the construction of locks and dams and a canal. In the 1970s after some test projects, the St. Louis District recognized that by working with rather than against nature, they could provide the congressionally mandated navigation channel while also providing environmental and social benefits and restoring or creating diverse aquatic habitats. This developed into decades of new and innovative strategies for engineering on the Mississippi River both in the open river and pooled reaches.
Innovation, Restoration, and Channel Maintenance on the Open River
The St. Louis District is required to provide congressionally mandated channel dimensions for navigation for Upper Mississippi River River Miles 300-0. On the open river reach of the Upper Mississippi River (UMR River Miles 195-0), this is achieved through dredging, rock removal, and the construction of river training structures. The St. Louis District works closely with a broad range of project partners who encourage us to develop engineering solutions that work with the natural tendencies of the Mississippi River while also creating broad stakeholder benefits including the creation and enhancement of environmental habitats. These solutions include modifications to the traditional river training structure designs to achieve desired results. These modified designs have resulted in the creation of shallow/low-velocity habitat, ephemeral islands, deep slack water scour holes, improvement of side channels, creation of mussel habitat, and the creation of vegetated islands.
The Middle Mississippi River is a dynamic system that naturally tries to change course through the creation of meander bends and channel cutoffs. These natural processes have resulted in reaches where a channel cutoff could occur. Rather than the design and construction of ‘hard’ engineering features to stop the channel cutoff potential, the St. Louis District has worked with project partners to work with nature to reduce cutoff risk while allowing the river to remain a natural system. One example is Thompson Bend where the solution to a potential channel cutoff was to work with local landowners to create a natural tree screen whose purpose is to reduce the energy of the river to stop destructive scour across the peninsula. Another example is at Dogtooth Bend where the District has joined informal collaborations with other Federal, State, local agencies, and NGO’s and Universities, to monitor the existing conditions of the peninsula and develop a comprehensive plan that addresses the missions of the stakeholders (e.g., flood risk reduction, environmental restoration, navigation, etc.).
Where dredging is required, the District is evaluating ways of using dredge disposal material to restore sandbar and island habitats, which are important habitats for the pallid sturgeon, a federally endangered species. Research is ongoing on other ways that dredge material can be used beneficially in riverine applications.
Environmental Pool Management
A series of locks and dams were constructed on the Upper Mississippi River, with most of the construction occurring in the 1930s. Although these structures provided a reliable navigation channel, they disrupted the natural hydrograph of the river which changed the environmental conditions and impacted the types of habitat that could survive. In the early 1990s, state and federal natural resource partners on the Upper Mississippi River asked the District to modify lock and dam operations at Lock and Dam 24 in Clarksville, Missouri; Lock and Dam 25 in Winfield, Missouri; and Melvin Price Lock and Dam in Alton, Illinois, to improve ecological conditions and restore some natural processes in the pools.
Environmental pool management restores form and function to the river by reestablishing natural processes and reducing large and rapid fluctuations in pool level. Managing for reduced water levels during the growing season mimics the natural cycle that existed before the construction of the lock and dam system on the Upper Mississippi River system, allowing for the growth of aquatic plants. To accomplish this, the St. Louis District slightly modified its operation, which resulted in increased the growth of aquatic vegetation during the summer while maintaining the authorized 9-foot (2.7-meter) navigation channel and staying within existing operating limits, a technique now known as environmental pool management. Over 30–40 days, the decrease in surface water elevations for about 160 kilometers exposes mudflats along riverbanks, around the perimeter of islands, and on the interior sloughs of islands, establishing optimal growing conditions. In 2015, the district began targeting 90 days of operation during the growing season, resulting in over 110 days of plant growth each year and reestablishing a perennial vegetation community of native arrowhead (Sagittaria latifolia) not seen since 1993. Since then, environmental pool management practices have consistently produced over 400 hectares of vegetation per year.
Alton Lake in Lower Pool 26
May 2017 when water elevations were at or near the normal pool.
July 2018 when water elevations were lowered for environmental pool management, while vegetation is growing.
May 2020 when water elevations were lowered for environmental pool management, before vegetation growth.
Due to the large success and broad stakeholder support of environmental pool management, the District is now considering ways to implement similar pool management practices at other dam operations within the District. Environmental pool management is also being piloted at other Districts’ Lock and Dam operations on the Upper Mississippi River.
Effective Partner Relationships Driving Innovation – River Resources Action Team
The design and implementation of engineering with nature projects are not possible without the trust, input, and support of project partners. The District has worked hard to develop and sustain close relationships with project partners to ensure that projects meet a diverse set of goals and objectives in addition to the engineering purpose. To formalize these relationships and coordination processes the River Resources Action Team (RRAT) was established in 2002 by way of a Memorandum of Understanding between the St. Louis District, U.S. Fish and Wildlife Service, Illinois Department of Natural Resources, and Missouri Department of Conservation. The RRAT was initially meant to formalize a coordination process to meet various regulatory, statutory, and procedural requirements of each agency as they relate to sustainable management of the Mississippi River within the U.S. Army Corps of Engineers, St. Louis District. Specifically, it provided a means for effective implementation of the reasonable and prudent alternatives (RPA) and reasonable and prudent measures (RPM) for the pallid sturgeon and least tern contained within the Biological Opinion covering Operation and Maintenance of the 9-Foot Channel Project and to provide a forum for coordination of 1) the Regulating Works and Channel Maintenance Programs; 2) the Upper Mississippi River Restoration Program and 3) other river management and operations programs.
Over the past two decades, the RRAT has since evolved into a highly valued collaborative mechanism for planning, prioritizing, and operating future St. Louis District Upper Mississippi River System projects/actions and for resolving any potential conflicts and disagreements regarding river management plans of the signatory agencies. The RRAT also serves as a platform for information exchange and data collection. The team approach has pushed the District to continue to develop innovative ways to fulfill our authorized responsibilities while helping to restore and protect ecosystem functions.
The RRAT continues to meet to coordinate a variety of Mississippi River issues, programs, and projects and remains a vital mechanism for communication among the signatory agencies. In addition, a regular coordination trip by boat down within the St. Louis District area of the Upper Mississippi is held to provide an opportunity for river engineers, environmental regulators, and concerned stakeholders to meet, to provide interdisciplinary project updates, and to communicate about the wider needs for river management. These meetings result in new ideas for additional river-training structures, identify potential project sites, and promote a better general understanding of viewpoints by developing relationships.