Company:
RBF Consulting, a Company of Michael Baker International and City of Newport Beach
Status:
Awarded
Awarded:
Environmental Engineering Project of the Year
Additional Files
Buck Gully Images
Additional Information

Buck Gully Canyon Restoration

Project Location:

Buck Gully Channel, Newport Beach, California

Project Description:

Buck Gully Canyon is located in the southern part of Newport Beach, between Corona Del Mar and Crystal Cove State Park. The creek runs through the canyon, and has a watershed of approximately two square miles. Historically, Buck Gully was an ephemeral creek; however, beginning in the 1990s, the hillsides of the watershed were developed with single family residences and the Pelican Hill Golf Club. Irrigation associated with this development resulted in additional inputs of water to the creek, so that now the creek runs perennially, with flows equaling approximately 17 million gallons per month during the dry season.
 
The project site is located on the lower portion of Buck Gully Canyon, seaward of Pacific Coast Highway and between the residential streets Hazel Drive on the north, and Evening Canyon Drive on the south. Single family residences are located on both edges of the canyon, their lots extending down to the middle of the canyon. The creek runs in a southwest direction, and flows out onto Little Corona Del Mar State Beach, which is within the Robert E. Badham State Marine Conservation Area, a designated Marine Protection Area.
 
The transition from ephemeral to year-long flows, increased runoff frequency and volumes, and a reduction in contributions of sediment due to development of the canyon edges, resulted in significant alterations to the hydrology of the stream within the project site, including significant erosion and degradation of the canyon. The increased flows scoured out the canyon bottom, leading to the lowering of the elevation of the stream and jeopardizing the canyon banks and adjacent existing development. Other effects included deposition of large amounts of sediment in the canyon bottom, split stream flows, incised channels, flows shifting away from the center of the canyon and stagnation of open waters.

The change in the pattern and volume of flows was mirrored with a change in the habitat of the creek. Increased flows resulted in the replacement of native species adapted to drier conditions with many non-native and invasive species adapted to wetter conditions. Erosion disturbed the canyon bottom, leading to disturbed morphology and habitat characteristics at the site. Existing native trees became low in abundance and had stunted morphology, and the understory at the site was unnaturally thick. Invasive species and non-native species were located throughout the project site, and the biodiversity as a whole at the site was reduced.

RBF provided planning, restoration design, and regulatory permitting for the construction of grading and erosion control improvements, and native re-vegetation for the stabilization and restoration of Lower Buck Gully.  The project included the reconstruction and restoration of the canyon through the use of grade control structures and bendway weirs.  Gabion (rock-filled) grade control structures were installed (and planted over with native willows) along the canyon to restore the stream invert to its original grade and to establish an equilibrium slope.  Bendway weirs were used to prevent future erosion by deflecting flows back to the main flow line and bank failures at critical bends in the stream.  Grading and native planting plans were prepared for the canyon to rehabilitate the stream to a more natural condition.

RBF provided detailed hydrology, hydraulic, and sediment transport studies for development of the final design.  RBF’s services also included obtaining permits from the California Coastal Commission, U.S Army Corps of Engineers, State Fish and Wildlife, and the San Diego Regional Water Quality Control Board.  The project required the dedication of easements from the adjacent properties to the City.  RBF worked with the City on outreach efforts to engage the property owners and coordinate meetings and workshops with the owners to gain consensus from the owners necessary for the project to be constructed.  The project was also augmented to treat surface water runoff from the existing developments in the tributary watershed.  Innovative subsurface wetland treatment facilities were designed in the stream between the gabion grade control structures to improve water quality for the downstream public beach.

Project Justification:

Buck Gully was in active decline due to upstream development. There was a loss of sediment entering the canyon and increase frequency and volume of storm runoff had been stripping sediment from the canyon bottom, resulting in downcutting of the streambed up to fifteen feet in the lower reaches of the canyon.  This streambed scour was evident in the lower reaches of the canyon (there was a fifteen-foot waterfall that was headcutting up toward Pacific Coast Highway). The continuing dramatic loss of sediment in the lower canyon caused several adverse conditions and threatened existing development along both sides of the canyon.

Without implementing measures to restore the streambed, the soil substrate would be lost due to severe erosion, thereby increasing impacts to the native plant community. With the loss of sediment, the defined limits of the streambed were significantly altered, resulting in multiple flow paths across the canyon.  One flow path migrated to the toe of the slope on the west side of the canyon, where it was eroding the slope buttress.

The successful rehabilitation of Buck Gully was a proactive initiative by the City of Newport Beach to protect the health of the canyon and protect existing development.  The project implemented measures to restore the creek to its normal water course and provide energy dissipation within the streambed, in a non-intrusive manner, which is necessary to maintain a stable equilibrium within the canyon.  The project’s mitigation measures were designed to protect the canyon bottom from a massive loss of sediment during large storm events, which in turn protects the buttress of the canyon slopes to forestall the potential for slope destabilization/failure, which could ultimately result in property damage for homeowners on the canyon edges.

Urban restoration projects are difficult as they often require significant stakeholder outreach, right-of-way acquisition and significant monitoring.  The Buck Gully restoration project occurred all on private land, requiring outreach to over 35 property owners.  In addition to tackling erosion and vegetation issues, the City and RBF designed subsurface flow wetlands, which further treat runoff from upstream sources prior to discharge at Little Corona Beach. 

Special Circumstances:

This complex effort required extensive coordination with numerous stakeholders, property owners, environmental regulators and consultants.  The project led to new relationships being forged and the strengthening of an existing relationship with the client, City of Newport Beach, leading to an additional contract to provide biological monitoring services for Buck Gully.  The 5 year monitoring program includes functional rapid assessment, qualitative and quantitative monitoring and the preparation of annual reports.  The reports will be submitted to four regulatory agencies.

Early monitoring results show an 80 percent decrease in fecal coliform and other lower constituent levels once water filters through the project site.  Furthermore, California Coastal Commission staff have called this a “model restoration project” as the Year 1 monitoring results found significant native vegetation cover and more diverse species (well beyond what what required in the regulatory permits).  The project begins formal biological monitoring again in Spring/Summer 2014.

Project Attachments:

NA

Award Citation::

The Buck Gully Canyon Restoration project was a successful effort in designing and constructing erosion control improvements for the stabilization and rehabilitation of Lower Buck Gully in Newport Beach.  This proactive effort, implemented by the City of Newport Beach, was successful in restoring the creek to its normal water course, forestalling the potential for slope destabilization/failure and returning the canyon to a more native state.

Suggested Award Summary:

The Buck Gully Canyon Restoration project was a successful effort in designing and constructing erosion control improvements for the stabilization and restoration of Lower Buck Gully in Newport Beach.  The project was a proactive effort by the City of Newport Beach to implement solutions to protect the health of the canyon.  The project implemented measures to restore the creek back to its normal water course, and provide energy dissipation within the streambed in a non-intrusive manner, that was necessary for maintaining a stable equilibrium within the canyon.  The specific measures used included bend-way weirs along the upper bend of lower Buck Gully to train the stream flows away from the toe of the slope; and stepped-gabion grade control structures in the lower reach to safely convey increased flood flows through this reach of the canyon.

RBF provided the City of Newport Beach with planning, design, and permitting for the stabilization and restoration of Lower Buck Gully.  RBF provided detailed hydrology, hydraulic, and sediment transport studies for development of the final design.  RBF’s services also included obtaining permits from the California Coastal Commission, U.S. Army Corps of Engineers, State Fish and Wildlife, and the San Diego Regional Water Quality Control Board.

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