Salmon River Estuary

The estuary is the nexus of intersections, where land meets sea meets salmon and cormorants, where salt water mixes with fresh. Among the most productive ecosystems on earth, estuaries create more organic matter per unit area than comparable forests, grasslands, or agricultural areas.

An estuary is an incredibly dynamic ecosystem, acting both as a transition and a buffer between salt and fresh water. Fresh water, nutrients, sediment, wood, dead plants, and flood debris from the surrounding forests travel down the slopes and into the river that flows into the estuary. This cornucopia of organic matter meets the brackish water, the incoming tides, and the fish and other organisms that either reside permanently in the estuary or come in temporarily from the ocean. Meanwhile an estuary protects adjacent land from floodwaters, both outgoing and incoming, and supports the vegetation and soil that help prevent erosion and stabilize shorelines.

Migratory birds rest and forage in estuaries. Many animals and fish depend upon estuaries and value them as nursery sites. In the Pacific Northwest, estuaries provide a vital link to the iconic salmon. On their way out to sea, young salmon shelter, forage and rest in estuaries as they make the physiological transition from fresh to salt water. On their return to spawn in the rivers where they were born, salmon swim back up the estuaries. Their dying carcasses add nutrients to the river and provide food for eagles, mink, bear, and river otters.

An intriguing feature of Pacific coast estuaries is their role as record keepers of monstrous subduction-zone earthquakes and associated tsunamis over the past six millennia. Magnitude 8 to 9 earthquakes off the coast trigger tsunamis every 500 years or so, and the rush of water and beach sand into the estuary leaves a distinctive mark in the sediment. Dating of these sand layers and studies of Japanese monks’ records have revealed that the last tsunami to affect the Salmon River estuary was in 1700 AD.

Thousands of years prior to the tsunami, Native Americans were already populating the Oregon coast. Native peoples worldwide have used estuaries for natural resources, for sustenance, and for cultural purposes. In general, the Native Americans lived in harmony with the estuaries of the Pacific Northwest, neither trying to tame nor overexploit them. With the arrival of white European settlers in the mid 1800s, estuaries began to change. The US government systematically forced the coastal Native Americans onto reservations and claimed much of their land for farming. By the early 1900s settlers were growing hay and grazing livestock all along the Salmon River estuary. As settlement increased, the estuary was diked to provide livestock constant access and to accommodate other farming uses. Many non-native plant species were introduced. Dike building and further settlement continued into the 1960s.

From 1969 to 1975, the Oregon coast’s first amusement park, Pixieland, operated on the banks of the Salmon River within the estuary confines. The 57-acre park contained a frontier village, amusement park rides, an RV park, and many dikes to prevent flooding. When the park closed its doors forever in 1975, the Forest Service acquired the property under the 1974 Cascade Head Scenic Research Area Act. This act called for the restoration of the estuary to its “natural condition,” ultimately involving the removal of all the dikes that had been built within the estuary. In conjunction with the dike removal that started in 1978, scientists began studying changes in the marsh vegetation.

They found that, like most wetlands, the estuary responded quickly to restoration attempts. A large portion of the pasture grasses and invasive weeds disappeared from the diked marshes. Because the tides were unable to bring in sediment behind the diked marshes and cattle were continually grazing, marsh floors had subsided. Their current elevation is below that of the only undiked or control marsh, partially explaining why the current set of species is more like a low salt marsh than the high salt marsh control. There is no telling how long it will take, if ever, for the marshes to succeed from low salt marsh vegetation to high salt marsh vegetation; it is a different phase of vegetation succession, not necessarily a negative condition.

Before the dikes were breached, the river served as a direct conduit to the sea. With the removal of the dikes, the natural channel systems in the Salmon River marshes have been generally restored, re-establishing feeder tributaries and backwater channels to the main Salmon River channel. Scientists have demonstrated that this has improved and increased habitat for insect prey, small crustaceans and other forage that juvenile salmon like to eat, plumping them up for their entry into the ocean. The improved channel systems also create more and varied shelter for the young salmon to rest.

Meanwhile, the ready mixing of salt and fresh water in the restored marshes helps these young salmon adapt to the saltwater environment they are about to enter. As well as being imprinted with the scent of their native stream, it has been surmised that time in the estuary is when young salmon are imprinted with the natural cycles and currents of the sea. Better and varied forage and shelter have expanded the range and the migration behaviors of the young salmon, resulting in healthier and more resilient fish populations.

There are four possible Reflections Sites in the Salmon River Estuary: Knight Park, Mitchell Marsh, Control Marsh and Tamara Quays.