The State of Missouri represented by the Missouri Department of Conservation, has partnered with the U.S. Army Corps of Engineers through the Planning Assistance to States authority for development of a comprehensive water resources plan. The Plan will address a water resources problem associated with flooding that frequently exceeds the current capacity associated with the Columbia Bottom Levee System and results in recurring costly repairs to the levee and closure of conservation area features amongst other challenges. The Plan will evaluate the technical, economic, environmental, and regulatory requirements to enable a levee setback and roadway modification/realignment across conservation area lands.
The Columbia Bottom Levee System is located at the confluence of the Mississippi and Missouri Rivers in north St. Louis County, Missouri. The levee is a non-federal system that is approximately 7.84 miles in length, with an estimated overtopping Annual Exceedance Probability of 20% (or 1/5 return period) reducing flood risk to an approximately 6.55 square mile area. Several parcels or individual landowners are located in the leveed area. The largest landowner in the leveed area is the Missouri Department of Conservation who purchased 4,318-acre area in 1997 to create an urban conservation area known as Columbia Bottom Conservation Area.
Frequent flood events are causing significant damage and destruction to the Columbia Bottom Conservation Area’s infrastructure rendering much of it unusable and inaccessible. This includes the levee, main asphalt road, parking lots, and confluence viewing platform. In addition, the frequency, depth, timing and duration of these major floods make it very challenging to manage the mosaic of bottomland habitats on the site. MDC efforts to reduce flood risk, repair damage, and intensively manage the area for waterfowl hunting are incurring costs to MDC through expenses, staff time, and resources that have become unsustainable and out of alignment with their mission to conserve nature and invest taxpayer funding wisely and prudently. MDC has identified the need to re-think the management goals of Columbia Bottom Conservation Area to create a sustainable balance between natural resources, human recreation, and financial investment.
The Corps of Engineers, with the St. Louis District as the lead and the Kansas City District as supporting element, will provide planning and engineering approaches to address the current failed levee segment including installation of a setback levee on the south side of the conservation area. This analysis will enable downstream flood risk to be reduced on neighboring properties and allow MDC to achieve its new management objectives. USACE will develop a Plan for the levee degrade and setback while maintaining the same overtopping AEP to the overall leveed area.
USACE will evaluate the alignment, necessary project features, types and quantities of material, sources of that material and provide rough order magnitude project cost, benefits, environmental, real estate and regulatory requirements. Our analysis will assist MDC in budgeting for more detailed project design and implementation of the levee setback and degrade.