A draft supplemental environmental assessment for adaptive management to the Sandy Point Bend chute complex in Harrison County, Iowa is currently available for public review.
The EA evaluates the environmental impacts of adaptive management measures to maintain shallow water habitat quality within the chute complex and prevent impacts to the adjacent navigation channel.
The original project was constructed in 2012 along the right descending bank of the Missouri River between river miles 657 and 658 to function as shallow water habitat intended to benefit the federally endangered pallid sturgeon and other native fish and wildlife species. The project consisted of two chutes with four intermediate tie channels connected to the main channel of the Missouri River.
Over time, the constructed chutes have become deeper and wider than designed, resulting in them currently pulling more water out of the Missouri River main channel than the original design specified. This has impacted shallow water habitat quality within the chutes and begun to adversely impact adjacent navigation channel depths.
Measures would include (1) constructing three stone sills across the three Missouri River tie channels to prevent the tie channels from flowing during low flows, (2) modifying existing control structures at the two main channel inlets to allow all life stages of fish (particularly larvae and young-of-year fish) the ability to access the complex, and (3) modifying control structures downstream of the inlets to control the amount of flow entering the chutes.
These adaptive management activities would rectify any adverse impacts to Missouri River navigation channel depths and improve habitat quality within the chutes by decreasing depths and velocities.
The proposed adaptive management activities would be made under the Corps’ Missouri River Recovery Program, which helps to fulfill the requirements of the U.S. Fish and Wildlife Service’s 2003 Amended Biological Opinion for the Operation of the Missouri River Main Stem Reservoir System, Operation and Maintenance of the Missouri River Bank Stabilization and Navigation Project, and Operation of the Kansas River Reservoir System.