Watershed Issues
Below is a summary of a few of the ecosystem threats we aim to address. This is not a complete look at the issues aquatic habitats face, but just some of the major problems we consider when improving aquatic habitat.
Riparian Vegetation
Plants need water, and water needs plants.
Riparian vegetation on Drift Creek (Siletz Basin)
Plants on the banks of streams have a multitude of benefits. Their roots stabilize sides of streams and reduce erosion. These highly productive areas sequester large amounts of carbon. The complex systems filter water before reaching the stream and groundwater, leaving cleaner water for humans and wildlife.
Fish inside the stream benefit from the riparian vegetation as well. The plants provide food and habitat for invertebrates that are food for young salmon and other fish. Trees that fall in the stream provide cover for small fish to hide. Tall plants provide shade for streams, keeping them at a temperature that can support cold water species like salmon.
MCWC and our partners have a heavy focus on planting in riparian areas. Strong riparian vegetation is central to watershed function and reduces the amount of management required my humans to reproduce ecosystem functions. Check out some of our planting projects under our habitat restoration projects.
Learn more about riparian areas
Stream simplification
complex, dynamic habitats are simplified for human land use.
Complex floodplain habitat on Big Creek
Healthy streams are not just one channel, they flow in interwoven braids above and below the ground. Fish rest in deep pools beneath fallen trees. Insects live under rocks in shallow riffles and feed the fish and birds. During high flows, the water floods over large, vegetated areas that provide temporary habitat and protection from the fast flowing water. Beavers build dams and create wide pools for young fish to grow. The tides push and pull their water where they flow into the ocean.
Human development requires predictable flows and reduction in flooding. Floodplains and tidal marshes are disconnected from natural flow using dikes and tide gates. Wetlands are drained through ditches to create dry land for development. Large trees are often removed from natural systems.
MCWC builds relationships with landowners, partners and stakeholders to maximize benefits to wildlife in balance with human use. We reconnect streams with their historic channels, place large wood into streams, and encourage the restoration of natural processes. Learn more about our habitat restoration projects.
Culvert replacements
Culverts protect infrastructure, but not all were built with nature in mind.
Failing culvert on Crazy Creek in the Alsea Basin
A nonfunctioning culvert can prevent aquatic life from moving through it, including salmon on their way to spawn. When flows are high, the water is too fast for aquatic animals to pass through the culvert. When flows are low, the erosion may cause a large gap between the stream and culvert that small animals cannot jump. These barriers can cut the journey of a fish on its way to spawn or access habitat short.
Directing the water through a small opening has drastic effects on the hydromorphology, or the shape of a stream over time. Upstream of the culvert, a large pool forms and causes swirling eddies that scour the edges of the pool. The high velocity output erodes the downstream side to bedrock.
Failing culverts can reduce the quality of habitat both close and far from the culvert. Fish and invertebates cannot remain in the fast water and bedrock near the culvert. Woody debris, gravel, and other natural parts of the landscape are transported long distances in streams and are vital for aquatic habitat, and an undersized culvert can prevent their transport.
MCWC has conducted large scale studies of our watersheds to understand where culverts are failing and coordinates with landowners and contractors to replace them. Check out our restoration projects to learn more.
Large woody Debris
Healthy Streams need large fallen trees, but many are missing
When large riparian trees fall into a stream or river, they affect the way water, rocks, and life move through the system as they decompose. History of land management on the Oregon Coast, and other places in the Pacific Northwest, has led to a lack of large wood in streams.
Benefits of large wood in streams. Illustration © The Nature Conservancy (Erica Simek Sloniker)
When a stream encounters a large log, it diverts the water and scours an area around the log. Over time, this generates pools and slow water areas that are refuges for salmon and other fish from high flows and predation. Breaking up water velocity prevents a channel from becoming incised, or eroding to become deeper and narrower, reducing the quality of habitat.
Salmon lay their eggs in gravel that accumulates in stream beds, and large wood prevents gravel and other materials from washing out of the stream unimpeded. Over time wood structures cause gravel bars to form upstream of them, further improving habitat quality and complexity.
A small nurse log with gravel bar build up (Mill Creek, Siletz Basin)
As logs break down, they become home to a suite of life. Fungi break them down, insects make their home, and new plants and even trees grow directly out of them. The biodiversity hosted in fallen logs, often called nurse logs, further improves habitat quality and food sources for salmon.
To hear how MCWC and our partners restore large wood in our working area, check out our restoration projects. If you have large trees you wish to donate to help create salmon habitat, check out our log salvage program.