Lassen Creek Restoration Project (Modoc County, CA)

The Lassen Creek Project has been in the works for over two years. Implementation started in August of 2005 and is expected to be completed by October. This project is based on “pond-and-plug” restoration technique designed to return stream flow to a more natural elevation, meander, and bankfull capacity so that the stream regains its historic interaction with the floodplain.

This method is commonly applied to incised stream channels where adequate floodplain is available to relocate the “design” channel. On Lassen Creek, the channel had been altered by irrigation ditches and past management practices that had severe impacts to the morphology of the channel.

As one of the key tributaries for Goose Lake redband trout, Lassen Creek was a top priority for action by the Goose Lake RCD and CA DFG. A plan was developed by StreamWise in 2003 and implemented in 2005. The plan included relocation of the stream from the irrigation ditch and incised channel to a constructed design channel in the center of the meadow. Extensive revegetation was conducted to promote stability in the first season of flow. The gully and irrigation channels were filled to floodplain elevation by excavating a series of ponds along the gully.

The project is designed to:

•  restore groundwater hydrology to the meadow

•  improve fish habitat and passage

•  reduce water temperature by reducing stream width

•  enhance the riparian corridor vegetation

•  reduce lateral erosion and downstream sediment transport

Photo Gallery - click to open thumbnails
Filling of the incised gully. (Sept. 2005)	Filled portion of the former irrigation ditch. (Design channel in background)
Constructed design channel with sod mat transplants. (Sept. 2005)

2009 Update To be honest, Lassen Creek has been the site of our most difficult challenges in restoring natural form and function to meadow stream channels.  Most of the initial project construction performed well, but heavy winter flows dislodged fresh sod mats that lined much of the design channel.  Our assessment indicated that the sod had not rooted into the banks, Also, the channel substrate in these reaches was not coarse enough to resist erosion during major flood events.  The flood events that caused the damage occurred just two months after the channel construction.
StreamWise proposed and implemented a repair technique along 2000’ of channel based on the observations of stable channel conditions in the remaining one mile of project length.  We noted that in every reach containing coarse bedload material, there was no measurable vertical incision.  In every reach where juniper revetment was used to protect fill material from lateral erosion, we found stable banks and recovering vegetation.  In the newly constructed design channel segments, where no revetment was used (only sod placement), and no gravel was added to protect the bed stability, we found evidence of lateral and vertical erosion following peak runoff events.
The repair work utilized locally available materials to mimic the stable channel conditions and restore the floodplain and channel connection in these sections.  Junipers were extracted, with root wad intact, and placed parallel to the flow line along each bank of the damaged channel.  Then gravel from a nearby lens of alluvial deposits was used to fill the void between the juniper trees lining the stream.  The end result was a reduction in cross-sectional area, coarsening of the streambed to match natural conditions, and underlying revetment to resist potential lateral or vertical erosion.

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Design channel with peak runoff damage. Spring 2006

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Packing gravel between juniper revetment. Summer 2006

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Same section as above at bankfull flow. Spring 2008

The repair work has held up well after two seasons with periodic overbank flow.  The entire project now has access to the floodplain at bankfull flow levels.  The borrow ponds remain partially filled in summer due to the increase in groundwater surface elevation.  Riparian recovery is underway and the pond edges are beginning to naturalize with native vegetation.
The lower meadow, pictured below, continues to recover following the pond and plug restoration project.  Some gravel was added to short segments of riffles, but no major repair work was required in this ½ mile reach.

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Spring 2008.  Design channel in lower reach (below road).

Lassen Creek provides invaluable lessons regarding application of pond and plug techniques for restoration of mountain meadow ecosystems.  StreamWise continues to monitor the effectiveness of the original project construction and the repair work required to insure long-term stability and recovery of the project site.

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