Project Location: The proposed bank site consists of an approximately 44-acre parcel along Beaver Creek, located west of Cobbler Avenue and north of 230th Street, within Section 21, Township 95 North, Range 18 West, Floyd County, Iowa. See attached location maps. Lat. 43.027017, Long. -92.978730.
Bank Objectives: The fundamental objective of compensatory mitigation is to offsetenvironmental losses resulting from unavoidable impacts to waters of the United States (WOTUS) authorized by Department of the Army Permits. Other objectives include: enhance and create additional wildlife habitat, restore native vegetation within the riparian buffer, widen the channel and pullback streambank slopes to increase cross-sectional area and stability, construct floodplain benches to provide a floodplain connection to frequent flows, and sell stream mitigation credits for project impacts proposed by other entities.
Project Description/Bank Establishment: The bank sponsor proposes to complete activities on approximately 44-acres of property owned by Naturion West, LLC. This project would result in the generation of emergent wetland and stream compensatory mitigation credits. The goal of this project is to restore 103.68-acres of emergent wetland, enhance 2.09-acres of forested wetland, establish 34.64-acres of buffer to generate an initial estimate of 7.56 wetland credits. The project will also restore 2,393.58 linear feet of stream with buffers to generate an initial estimate of 54,792.86 stream credits.
A. The proposed concept alignment would shape streambanks along 1,304.98 linear feet to increase the cross-sectional area of the stream, reduce shear stress, reduce velocities which will reduce erosional effects within the stream channel and adjacent floodplain. In addition, a floodplain bench about 5 to 10 feet in width will be added along 1,088.60 linear feet at a 10:1 slope. The floodplain bench will transition at a 4:1 slope to the existing floodplain elevation. The proposed channel will provide floodplain connectivity, particularly to the proposed 1.5-2-year low floodplain benches; increasing the frequency of flooding of the riparian fringe. The overbank floodplain inundation is controlled by downstream road crossings, culverts, and stream hydraulics for the larger/less frequent storms.
B. There are two rock riffles proposed. One at the upstream terminal end of the project and a second at approximately the midpoint of the project. Each riffle will be comprised of rock revetment with sloping upstream and downstream faces. The riffles will provide grade control to help stabilize the stream. Additionally, two existing beaver dams were in rough shape post flooding during spring 2024; however, they provide minor grade control. Two beaver dam analogs (BDAs) are proposed to improve hydrology and floodplain connectivity. Similar to dams built by beavers, BDA complexes will change the spatial distribution of water and increase retention time in the drainage area.
C. Wetland restoration is proposed south of Beaver Creek on the east side of the Bank. Topographically, this area is at a lower elevation. Grading will continue slightly into the riparian buffer within the floodplain to tie into natural contours. This depressional emergent wetland will receive floodwaters, precipitation, and overland runoff. Wetland surface area will comprise approximately 5.0 acres and the average depth will be 1.5 feet.
D. Other improvements include restoring diverse riparian buffer habitat. Restoration efforts include seeding the current row-crop field within the buffer with native mesic species. Vegetation within the riparian buffer will be managed with mowing, prescribed fire, herbicide, and native seed. The Bank would be seeded with appropriate native ecotype seed mixes.
E. Additional information on construction techniques, target plant community types, and detailed planting plans will be completed prior to the submission of the draft Mitigation Banking Instrument.
Service Area: The proposed mitigation bank will be in the Cedar Service Area.
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