Working with Bellevue Park’s staff, ICF developed a stream and wetland restoration plan that was submitted to local, state, and federal agencies for approval. The restoration plan focused on relocating a portion of the stream to its historic channel.
The plan included installing log structures along the bank for bank stabilization, placing other log structures with root wads in the remaining portion of the stream to establish pools and glides, and placing a spawning gravel streambed mix along the restored channel bottom. ICF coordinated with bridge engineers to improve channel hydraulics through bridge replacement (i.e., bridge span length, placement of wing walls, and bridge deck height above 100-year flows). A maintenance bypass channel was designed to avoid impacts on flows and fish during the maintenance activities.
Another unique feature of the project is an in-line sediment pond designed to capture sediment originating in the upper basin outside the park. ICF designed the sediment pond to provide capacity and minimize maintenance dredging. The sediment analysis module (SAM) in Hydrologic Engineering Centers River Analysis System (HEC-RAS) was used to estimate sediment transport capacity through the project area. These elements were coordinated with the permitting agencies and ultimately authorized due to their necessity to the restoration.
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