During the late 19th and early mid-20th century, most of the wetlands along the lower Coquille River valley were drained and converted for agricultural use, to take advantage of the fertile soils of the lower river valley, which are rich in organic matter and naturally sub-irrigated. In some areas, dikes or levees were constructed and tide gates were installed to allow freshwater to drain out, while holding back incoming tide water. It was a common practice for wetland channels to be ditched into straight lines to create square areas of land. This optimized the amount of grazeable land for livestock but reduced critical habitat for juvenile fish.
Over the years, increased understanding of the ecologic importance of floodplain habitat connectivity and slow water refugia to the salmonid life cycle have led to increased regulations regarding fish passage at both the State and Federal level. Many tide gates and dikes along the lower Coquille River no longer function well and need to be replaced to maintain healthy pasture lands. But to replace them in accordance with current fish passage regulations requires a complex technical process, often employing an engineer or private environmental consultant to assist with design and permitting. The average landowners in Coos County tend to lack the technical expertise, the time, or the financial capacity to complete such projects entirely on their own. Some landowners take matters into their own hands and perform repairs despite the regulations; however, this can expose the landowner to potential regulatory enforcement actions.
Some landowners have partnered with local conservation groups such as the Coos Soil and Water Conservation District, Coquille Watershed Association, or Coos Watershed Associations, to pursue grant funding to pay for drainage infrastructure upgrades that comply with the fish passage rules. This has resulted in a new brand of restoration projects, referred to as "Working Landscapes" projects. These habitat enhancement projects aim to rebuild agricultural drainage infrastructure and replace old failing tide gates and undersized culverts with new, fish-friendly designs and to partially restore tidal or wetland channel habitat on working farms. The Coos Soil and Water Conservation District is currently managing six Working Landscapes Projects in the Coos and Coquille basins, as well as supporting our partners, the Coos and Coquille Watershed Associations, with several ongoing related efforts.
Although not the first of its kind, the North Bank Working Landscapes Project is one such project aimed at tackling the problem of increased flooding and crumbling water control infrastructure on the lower Coquille. The owners of the North Bank project site first approached the Coos SWCD in 2017, with concerns about erosion of the dike that protected their farm from the river’s salty high tides. From those early discussions, a plan was developed that proposed to not only repair the failing dike, but also to replace the old, 1ft diameter culvert and associated top hinge “mud flap” tide gate with a new, appropriately sized, side hinge aluminum tide gate. Drainage channels in the pasture would be redesigned and graded for better drainage and increased channel habitat complexity. Fencing would be built along the channels to protect them from livestock and native plants would be planted along the channels to stabilize the banks and provide fish and wildlife habitat.
In 2018, the Oregon Watershed Enhancement Board awarded $58,333 to the Coos SWCD to design and permit the proposal. Since then, Coos SWCD has worked extensively with the Oregon Department of Fish and Wildlife, the Coquille Indian Tribe, and the landowners to make the project design a reality. An engineering consultant was hired to proof and vet designs and assist with permitting. Grant funding for construction was sought and delayed by the pandemic in 2020-21, but in September of 2022 Phase I Construction was completed, which saw the installation of a new 7.0 ft diameter Weholite HDPE culvert and side-hinge aluminum tide gate and MTR by Nehalem Marine, LLC. This will allow fish to have greater access to the site than they have had for nearly a century. The next Phase (Phase II Construction) will involve a pullback and reconstruction of the eroding dike, as well as construction of the re-meandering tidal channel network. The remainder of the proposed work is slated to be completed in 2023-24.
After completion of the remaining project objectives, a comprehensive solution to grazing and fish habitat will be created. The new tide gate is equipped with a Muted Tidal Regulator, which is a device that will allow tide water, and fish, to move into and out of the restored tidal wetland channels for longer windows of time, over greater portions of the year. The tide gate and MTR will be managed in accordance with a seasonal water management plan.
Typically, the gate will be set to close when the interior channels are full to prevent the adjacent pastures from flooding during times of year when flooding is undesirable. The pastures will be protected from tidal saltwater flooding in the summers, so healthy forage grass can grow for livestock grazing and hay production. During the winter season when pastures are not in use, a higher level of tidal exchange and flooding of the fields can occur. Fish will be able to move between the river and wetland channels with every tide. This is very important because once in the wetland channels, fish are better able to forage for food without worrying about the heavy currents and predatory bass in the lower Coquille River mainstem. Studies have documented that juvenile coho salmon that have access to wetland channels for rearing grow larger and have a higher chance of survival on average than fish reared in the mainstem river. The project is also designed to gradually provide some thermal refugia in the summer, when the mainstem river reaches temperatures that can be devastating to juvenile salmonids.