After: Live posts and toe stone protection help
keep stabilized bank in place.
Before: Eroding bank and invasive plants.
Village of Gates Mills Chagrin Riverbank Stabilization
The Village of Gates Mills completed a bio-engineered bank stabilization project in April 2019 to address erosion on three privately owned parcels between Old Mill Road and Chagrin River Road. This section of the Chagrin River is designated State Scenic and supports recreational fishing; however, upstream development contributes to increased stormwater runoff and bank destabilization. The excessively eroding bank was a major source of sediment to the Chagrin River. Prior to restoration, water runoff from rainstorms rose into the floodplain and further eroded the riverbank as the water receded into the stream channel. The riverbank lacked deep-rooted native plants to hold soil and sediment in place. The stabilization project is helping to minimize this erosion. The construction team installed toe stone protection and a series of seven short bendway weirs on approximately 400 linear feet of riverbank and planted native vegetation along 7,500 square feet of the stream to stabilize the banks, reduce scour and filter out pollutants.
Toe stone protection is a row of stone placed parallel to the stream at the bottom of the riverbank. It supports the weight of the bank, and in time, stabilizes the slope by the deposition of sediments behind the row of stones. For this project, the team filled the area behind the stones with smaller cobble and gravel. A bendway weir is a structure made of stones that jut into the stream channel. This project’s seven bendway weir structures, each made of two large boulder stones, “lean” into each other to stay secure and help deflect the river’s energy away from the bank. The series of weirs promotes natural sediment deposition of material between the weirs and creates in-stream habitat for fish and aquatic insects.
The team prepped the planting area by treating non-native, invasive plants with an herbicide safe for use near waterways or removing plants by hand. Invasive species at this site included Japanese knotweed, privet, bush honeysuckle, garlic mustard, Callery pear, and butterbur. The team planted live stakes and posts (dormant cuttings of native shrubs driven about 2/3 of the way into the bank) and containers of native, woody plants. Live stakes are about 2-feet long whereas the live posts average about 6 feet long (1-1.5 inches diameter). The plants’ fibrous root systems provide long-term riverbank stabilization and their leaves and stems protect the riverbank from the flowing water and enhance wildlife habitat. Examples of native plants installed as part of this project include the following shrubs: Winterberry, Silky Dogwood, Redosier Dogwood, Northern Bayberry, Buttonbush, Ninebark, Pussy Willow, Silky Willow, and Sandbar Willow. The team seeded all disturbed areas within the project area and voids between rocks with a native riparian seed mix with herbaceous plants such as Butterfly milkweed, Smooth Blue Aster, Partridge Pea, Blackeyed Susan, Ohio Spiderwort, and Wingstem.
This project was financed in part through a grant from the State of Ohio Environmental Protection Agency and the United States Environmental Protection Agency, under the provisions of Section 319(h) of the Clean Water Act. This project is included in an Ohio EPA and USEPA approved nonpoint source implementation strategy plan (NPS-IS), the Griswold Creek-Chagrin River plan.
The Watershed Partners assisted the Village of Gates Mills in applying for Ohio EPA Section 319 grant funding in 2016. The grant application had a total budget of $349, 578. Private property owners contributed the required 40% matching share of $139,831 and Ohio EPA awarded $209,747. The Watershed Partners assisted the Village with developing a request for proposals to hire a qualified consultant to design and build the project, reviewing project plans, coordinating with landowners, education and outreach related to the project, and administration of the Ohio EPA grant. Davey Resource Group was selected to design and construct the project and develop a long-term maintenance plan. The project was authorized with a Director’s Authorization by Ohio EPA under Nationwide Permit 13 which allows bank stabilization activities to prevent erosion.
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