Restoring Angora Creek

 

 

Prepared by Cyndie Walck

Sierra District

California Department of Parks and Recreation

 

The California Department of Parks and Recreation (CDPR) restored a reach of Angora Creek and the adjacent meadow, approximately one mile upstream of the confluence with the Upper Truckee River. The project site is located in Washoe Meadows State Park, approximately 1.5 miles north of Meyers and 2.5 miles south of the city of South Lake Tahoe in El Dorado County, California.  

 

Land use impacts, including sewer construction, and grazing, had degraded stream function and stability, as well as wildlife habitat and water quality.

 

A section of Angora Creek once meandered through a wet meadow, but the stream was captured by the South Tahoe Public Utility District (STPUD) sewer alignment when the sewer was constructed in the 1960s.  The excavation for the line follows a route straight down the slope of the meadow and it was not re-vegetated, leaving the path vulnerable to erosion.  The stream deviated from it’s original winding path to flow in a straight line directly on top of the sewer.  

 

It flowed directly from manhole to manhole for 

approximately 2,000 feet.  The straight path 

gave the stream more power,

so the stream eroded it’s bed and banks.   

 

Immediately downstream, the next 1,000-foot-long section of the channel had down-cut, scouring the bed of the stream to two feet below its original elevation.  This in turn caused the meadow to dry out and critical habitat was degraded.

 

CDPR restored the stream in fall of 2002. Project manager, Cyndie Walck, secured grant funding from the Lahontan Water Quality Control Board and the California Tahoe 

Conservancy.  

 

She then worked with Haen Engineering and River Run to 

do a natural channel design, and contracted with Watershed Science to do the construction. A new 

meandering channel was constructed in the meadow, 

and the sewer channel was filled. 

 

The 3,800-foot-long new channel mimics the shape and layout of the 

pre-disturbance channel.   

 

It is very sinuous (curvy) and is less deep and wide than the eroded channel.  This in turn causes the water to spread out on the meadow 

more frequently and raises the elevation of the groundwater in the 

meadow, improving habitat.  Both the new restored channel and the old captured alignment were re-vegetated using native plants.

 

The objectives of this project were to decrease erosion, enhance wetland and riparian habitat and to improve water quality by restoring the stream channel to a geomorphically functioning condition away from the sewer line.  In addition, restoration of the bed elevation and sinuosity of the stream restored access to the meadow floodplain, raised groundwater elevations, increased sediment deposition and nutrient removal and improved meadow health.

 

A ¾ mile section of creek and 20 acres of adjacent meadow were restored by this project. Cost, including planning, design, construction, re-vegetation, and monitoring was approximately $550,000. 

 

The project has been a great success with the new channel functioning properly, the water table elevated and the vegetation responding with 

lush wet species and improved the meadow habitat.