By Richard Beck and Julia Fine
Michael Baker International, Inc.
July 16, 2020
Buck Gully Canyon is located in the southern part of the City of Newport Beach, California between Little Corona Del Mar Beach and Crystal Cove State Park within the Robert E. Badham State Marine Conservation Area, a designated Marine Protection Area. Buck Gully 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, resulting in a perennial stream with flows equaling 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 project area has many varieties of native plants along the canyon slopes.
Buck Gully was in active decline due to upstream development. The transition from ephemeral to year-long flows and increased runoff frequency and volumes resulted in significant alterations to the stream hydrology. The increased storm runoff had been stripping sediment from the canyon bottom, lowering the elevation of the stream and jeopardizing the canyon banks and adjacent existing development. This was exacerbated by a loss of sediment entering the canyon from development of the canyon edges. The streambed was down cut up to fifteen feet in the lower reaches of the canyon. There was a fifteen-foot waterfall that was headcutting toward the Pacific Coast Highway.
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. 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. 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.
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. 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.
To address and mitigate negative impacts to the area the canyon was reconstructed and restored 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.
Restoration required persistence and complex coordination to work through regulations and obtain 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. Significant coordination occurred between the project team and these four regulatory agencies to identify and concur on a design that satisfied all permitting requirements and would achieve the desired outcome. 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. The subsurface flow wetlands further treat runoff from upstream sources prior to discharge at Little Corona Beach.
The project also included extensive outreach efforts to engage adjacent property owners and coordinate meetings and workshops with the owners to gain consensus. The Buck Gully restoration project occurred exclusively on private land requiring the dedication of easements from over 35 adjacent properties to the City.
The successful rehabilitation of Buck Gully is a wonderful example of a proactive initiative by the City of Newport Beach that protects both the health of the canyon as well as existing development while creating invaluable natural space in the community. 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.
Following the successful completion of the stream and habitat restoration, a restoration monitoring program ensued which included functional rapid assessment, and qualitative and quantitative monitoring.
Monitoring results show an unexpected 80 percent decrease in fecal coliform and other lower constituent levels once water filters through the project site. California Coastal Commission staff have called this a “model restoration project” as the monitoring results indicate significant native vegetation cover and more diverse species. This project is a model for how stream restoration can provide benefits to stream hydrology, water quality, and native vegetation while increasing community resilience and quality of life.
Richard Beck is a Vice President/Practice Executive of Planning, GIS and Survey/Mapping disciplines in Michael Baker’s Santa Ana, California office. He holds a BS in Environmental Studies from the University of California, Santa Cruz and is a Statewide Instructor of the CA Rapid Assessment Method (CRAM)- training students and practitioners this functional based wetland assessment. He is a Professional Wetland Scientist (PWS), Certified Environmental Professional (CEP), and Certified Ecological Restoration Practitioner (CERP).
Julia Fine is 2005 Lafayette College graduate with a BS in Civil Engineering and a 2010 Villanova University graduate with a MS in Civil Engineering. She currently works at Michael Baker International, a full service engineering firm, as a Project Manager with 15 years of Water Resource experience in Hydraulics & Hydrology, Stormwater Management, Drainage Design, and Erosion and Sediment Control. She can be contacted at firstname.lastname@example.org.