USA: Corps Repairs Rock Structures Along Missouri River
The Kansas City District has announced that the Missouri River Bank Stabilization and Navigation Project (BSNP) has received over $31 million of Disaster Relief Appropriations Act (DRAA) funding to repair flood damage to the river rock structures that comprise the BSNP. This is in addition to over $45 million already received in DRAA funds to repair damaged levees within the district.
The structures of the Missouri River BSNP were authorized and designed to provide a reliable navigation channel and prevent meandering of the river. The project was completed in 1981 and is maintained by the Corps of Engineers using annual appropriations from Congress. Damages to the project from the 2011 flood required DRAA funding because annual appropriations of $4 million are insufficient for required repairs. The BSNP structures will be repaired to the elevations as specified in the maintenance criteria established in the 1970s and to the lengths that existed prior to the flood. Despite sustaining significant damage during the 2011 flood, the structures performed as designed, preventing cutoffs or river channel re-routing that would have occurred without the BSNP.
The DRAA funds will be used for repairs to river structures in the Kansas City District’s area of responsibility, which extends from Rulo, Neb., to St. Louis. Throughout the past winter and into the spring, the Kansas City District has been actively evaluating the condition of the river after the historic 2011 flood event and assessing system vulnerabilities prior to the start of the commercial navigation season. Inspections of the Kansas City District structures have shown that approximately 400 of the existing 5,000 river rock structures have significant damage; eight locations have navigation channel impacts, and substantial erosion of the bank line has occurred along the entire length of the river.
Riverbank erosion from the 2011 flood event was much greater than normally experienced. Although the BSNP structures tend to reduce bank erosion, they were not explicitly authorized or designed for this. Some level of erosion occurs during every flood event. Direct repair of the flood-induced bank erosion is not part of the BSNP authorization or DRAA funded repairs. However, repairing the BSNP structures will assist in restoration of eroded banks and will restore the equivalent level of erosion protection that existed prior to the flood.
The first construction contract using these DRAA funds has been awarded, and work has started on river structures at Missouri River mile 475 to river mile 480 at Holt County, Mo., and Doniphan County, Kan. Additional contracts will be issued and awarded to complete identified repairs. The last of the repair contracts is scheduled to be awarded by September 30, 2012, and will take several years to complete due to extensive damages from the 2011 flood.
Another component of work on the river consists of mitigating for environmental damages caused by the construction of the BSNP. Mitigation includes building of side channels and some rock structures to create shallow water habitat. Constructed chutes that have eroded excessively due to prolonged high flows or due to compromised grade control structures are being addressed in seven locations in the Kansas City District. When appropriate, Missouri River Recovery Program (MRRP) funds are used for actions to address the amount of flow in chutes and/or erosion concerns associated with MRRP projects. To date, two of the seven chute sites have already been addressed, and work is ongoing at a third site. Detailed assessments of the performance of shallow water habitat sites and the effects on other authorized purposes will be ongoing as additional concerns are identified.
Dredging Today Staff, May 1, 2012; Image: usace