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Geomorphic Investigation of Quinault River, WA, 18 Km Reach Upstream from Lake Quinault

In an effort to better understand what opportunities exist to restore sockeye salmon habitat, the Bureau of Reclamation (Reclamation) was asked to undertake a geomorphic evaluation of the Upper Quinault River on the Olympic Peninsula in northwest Washington State. The Upper Quinault River as described extends for 18 river kilometers (RK) (11.2 miles) from the upstream end of Lake Quinault (RK 0) to the junction of the North and East Forks of the Quinault River (forks) near the National Park Service Bridge (RK 18). The East Fork Quinault River is also commonly referred to as the mainstem fork of the Quinault.

Quinault River Study Area

Quinault River Study Area

The river has changed markedly since the late 1800s, largely as a result of clearing of mature forests and large woody debris in and around the river area in the late 1800s and early 1900s. We propose the river was in a state of transition to a new altered condition in the early 1900s in response to the removal of large woody debris and increased sediment load from vegetated islands and terraces that were eroded. Areas that were clear cut changed river processes to a greater degree than did areas where only the largest trees were selectively cut. After vegetation was removed, relatively stable hard points were gradually lost along the course of the river and have not been naturally replaced due to the lack of mature forest from which to develop new stable hard points. Once these hard points were gone, the river was free to migrate across the floodplain at a faster rate. The more rapidly migrating river liberated large amounts of sediment that had been stored in bars, vegetated islands, and the floodplain. The sediment supply quickly increased above natural levels. At about the same time, removal of vegetation on the adjacent terraces made terrace banks more vulnerable to erosion by the river during floods. This bank erosion, in addition to destroying property and roads, further increased the amount of sediment input to the river and resulted in a large loss of historically stable terrace channels.

Vegetation Age

Map of Vegetation Age

Increased channel migration, channel bank and terrace erosion, and the consequent reduction of the number of spawning salmon in the Upper River would also cause a decline in water quality and trophic productivity within the rearing environment of Lake Quinault. This is a critical phase for over all productivity of the system, and poor conditions in the Lake would act as a bottleneck that would limit production. Deteriorating conditions in Lake Quinault likely occurred simultaneously with changes occurring in the Upper River to affect and limit the capacity of the system to produce sockeye salmon.

Landowners whose property and infrastructure directly abut the active channel run the greatest risk of continued bank erosion and loss of land. Surfaces on the south shore near Lake Quinault may contain old lake bed deposits (clay) that have more ability to resist erosion than upstream more erodible alluvial terrace surfaces. Landowners within the backwater influence of Lake Quinault have also been subjected to repeated flooding. However, while some degree of flooding can be tolerated, eroded property cannot be easily recovered. Over the last century river-front landowners have responded to loss of property and endangered infrastructure by re-arranging or removing large woody debris and log jams in the river and placing cabled logs and rock riprap along the river bank to try and limit erosion. This approach has in places worked, but can also cause unanticipated effects to other land across or downstream from the site protected. In some cases this has limited habitat availability because entrances to side channel become blocked with fill or levees. Recently some landowners have begun replanting of forest along bank lines and are interested in additional short-term protection strategies that would help limit erosion risk.

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