Yaquina Bay 2D Hydraulic Model Development

This project will complete 10% engineering designs and prepare a 2D hydraulic model of the historic Yaquina River Oxbow known as the Boone and Nute Slough Watershed (BNSW) and the immediately adjacent Yaquina River channel at the slough mouths. Our intent for the 2D model is to allow for additional questions to be answered, such as how many muted regulator gates would be needed to meet fish passage requirements, or how large of a bridged channel opening would be needed for fish passage requirements. This model will be utilized to create and evaluate up to five alternatives that will inform property owners within the BNSW about potential options for water and land management and habitat restoration, including tidal reconnection, under current conditions as well as with sea level rise projections. Project partners include the MidCoast Watershed Council, the Confederated Tribes of the Siletz Indians, McKenzie River Trust, private landowners within the BNSW, and a contracted technical engineering firm.

This modeling project will help inform one of the FIP’s highest priority tidal wetland restoration projects within this Focused Investment Partnership (FIP) initiative. Tidal wetland restoration is shown to increase the habitat quality and quantity for juvenile salmonids, especially when considering Life History Diversity and early estuary rearing of coho and Chinook. Chum salmon benefit as they are among the earliest estuary rearing after hatching out of the gravel in freshwater areas. Tidal wetland habitats provide energy-rich and abundant insect and amphipod populations for juvenile salmon foraging. Provision of nutritious prey leads to higher salmon growth rates and longer stays in the estuary, leading to higher adult survival rates. Studies conducted in the Columbia River estuary have linked estuary restoration (mostly of marshes) to increased habitat capacity, resulting in higher prey (insect and amphipod) densities, and higher juvenile growth rates. Increases in juvenile growth rates relate directly to survival.