WATERWAY AND LOCATION: The project would affect waters of the United States associated with the Yellow River. The project/review area is located west of 111th Avenue to the south of Moneek, Iowa in Section 14,Township 96 North, Range 7 West; at Latitude 43.138399 and Longitude -91.629505; in, Winneshiek County, Iowa.
EXISTING CONDITIONS: The project is located on a segment of the Yellow River that has experienced bank destabilization and erosion.
PROJECT PURPOSE:
- Basic: Streambank erosion protection
- Overall: The overall project purpose is to reduce streambank erosion in the Yellow River.
PROPOSED WORK: The applicant has proposed authorization to stabilize twelve streambank segments totaling 3,411 feet along the stream corridor. Methods utilized will be done using a technique of Longitudinal Peak Stone Toe Protection, Stone Toe Protection with Floodplain Bench, and Stone Toe Protection with slope above rock. The design includes 1,108 feet of stone toe protection, 470 feet of stone toe protection with a constructed floodplain bench and 1,833 feet of longitudinal stone toe protection.
Stone toe protection involves grading the streambank back to a 2:1 slope and lined 4 vertical feet high and 2 feet thick with rock rip rap. Above the lined rip rap stone, the streambank will be shaped to a 4:1 slope and seeded to native vegetation and covered with coir erosion control blankets. Stone toe protection with floodplain bench will have a 15-foot flat bottom bench installation above rip rap and then slopped 4:1 above the bench. In stream boulder clusters and bank root wads will be incorporated into the project to maximize aquatic habitat restoration.
Four stream crossings will be installed at critical locations along the stream corridor to allow for stable crossings for cattle and help exclude cattle from banks. Oxbow wetland restoration will occur on South oxbow and consist of excavations to remove depositional alluvial material over the historic stream channel bed. The site will be reseeded to diverse native wetland vegetation.
Bank and oxbow excavation will occur with Rock-Rip rap placed on bank toe up to 2 feet above normal high-water mark. Oxbow excavations will reach the historic channel bed and be staged back until the oxbow to resemble the natural elevation changes from the upstream end to downstream end of the oxbow. In channel 3 feet x 3 feet boulders will be placed to create habitat, and tree root wads will be strategically installed to add woody habitat features.
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