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Case Study - Asotin Creek - Meander Reconstruction

January 1, 1997, was an eventful time for Asotin Creek, Washington residents. In a period of less than a year, two large flood events occurred, causing extreme damage at numerous sites throughout the watershed.

The ordinary high flow (often referred to as channel forming or bankfull flow) is the natural size channel a river will seek, over time. Asotin Creek’s flows exceeded the ordinary high flow 10 times at Asotin and Headgate parks.

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Figure 1: The J. Bar S. winter feeding area.
This area received floods more than 10 times the ordinary high flow.

One impacted site is on the South Fork of Asotin Creek. This site, referred to as the J. Bar S. winter feeding site (Figure 1) and owned by Jake and Dan Schlee, received floods more than 10 times the ordinary high flow. Previous to January 1, the stream was located over a hundred feet away from the haysheds and feeding area. When large amounts of rock, cobble, and gravel collapsed into the right side of the stream corridor, the entire channel was directed toward the winter feeding area and hayshed. This redirection of flood flows undermined and eroded away thousands of tons of valuable topsoil and property, threatening the loss of the hayshed and corral. Fences and alternative water sources were destroyed. The challenges for stream restoration at this site were numerous because of the potential bridge constriction at the bottom, excessive downcutting, and limited area within which to work (Figures 2 and 3).

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Figure 2:South Fork of Asotin Creek restoration site before reconstruction.

Figure 3:After reconstruction.

The Asotin County Conservation District put an interdisciplinary team together in the spring of 1997 to develop a plan and alternative for the J. Bar S. site. An innovative approach referred to as meander reconstruction was proposed by the interdisciplinary team to correct the problem and restore some natural capabilities of the stream. It was accepted by the landowners and Asotin County Conservation District. Some natural capabilities are the dissipation of flood energy over floodplains and maintenance of a stable ordinary high flow channel.

Additional benefits to the approach would be to reestablish proper alignment with the bridge and restore fish habitat. This alternative was installed within the last 2 weeks of September, 1997. Care was used to move young steelhead out of the old channel while the new meandering channel was built. Other practices on site such as alternative water sources and fencing are soon to follow.

The meander reconstruction was designed to address both the landowners’ concerns and stream processes. Although on-site stream restoration cannot resolve problems higher up in the watershed, it can address immediate concerns regarding fish habitat and streambank stability. Numerous pools with woody debris were introduced to enhance salmon rearing and resting habitat. The pools were designed and set to a scour pattern unique to this stream type. This meander reconstruction is the first of its kind in the state of Washington.

The principal funding for this project was provided by the Bonneville Power Administration (BPA). The BPA funds are used to help implement the Asotin Creek Model Watershed Plan, which is part of the Northwest Power Planning Council’s “Strategy for Salmon.” The moneys for funding by BPA are generated from power rate payers in the Northwest. The purpose for funding is to improve the fish habitat component of the “Strategy for Salmon,” which is one of the four elements referred to as the four H’s— harvest management, hatcheries and their practices, survival at hydroelectric dams, and fish habitat improvement.

Table 1: Project costs (original estimate in April,1997 was $26,000)
Project Cost
Reconstructed meanders $10,200
Upstream revetments $2,800
Fencing $400
Riparian/ streambank plantings and potential operation and maintenance $3,500