Coaledo Tide Gate Replacement for Fish Passage Improvement

The Coaledo Drainage District (CDD) is a 9,800-acre drainage along the main-stem Coquille River in Coos County, Oregon. CDD contains 11.4 miles of coho salmon habitat and 490 acres of tidal wetland habitat, of which 289 acres are restored wetlands protected in perpetuity by ODFW. However, this area has been converted from its historic state by clearing, leveeing, tidegating, and draining for agricultural purposes. These actions have led to the degradation of tidal wetland habitats and/or restricted access to remaining wetland and tidal channel habitats for juvenile coho and Chinook salmon, as well as other species. Lack of slow-water refugia and off-channel habitat is a critical limiting factor affecting Oregon Coast coho populations with the access and restoration of tidal wetlands being a top priority action for recovery. To address these limiting factors, CoqWA has partnered with CDD, The Bridges Foundation, private landowners, ODFW, Coquille Indian Tribe (CIT), and the Coos Soil and Water Conservation District (CoosSWCD), with the assistance of River Design Group (RDG) and Nehalem Marine to implement a working lands restoration project that promotes ecological, economic, and social resiliency in the Coquille watershed. This project will improve fish passage and restore hydrologic connectivity by replacing current deleterious infrastructure with three 8’x10’ box culverts, each fitted with an aluminum side-hinged tide gate and Muted Tidal Regulators to control upstream inundation and duration of gate door openness.

The Coaledo tide gates are restricting juvenile salmonid movements from mainstem Beaver Slough downstream to highly valuable wetland and slough habitats upstream. Monitoring data shows juvenile coho staging for extended periods of time downstream of the gate to gain access to these habitats. Replacing these tide gates will maximize fish passage without negatively impacting private landowners and infrastructure upstream. This project will result in a tidal regime that more closely resembles historic conditions. Projects like these are critically important for ecological and community resiliency to mitigate the effects of climate change, such as rising stream temperatures and more volatile storm events.