.png)
Topanga Lagoon Restoration Project Overview
Background
Topanga Lagoon, located within Topanga State Park, is a special place – it is one of the last remnants of a coastal wetland in California. Its unique mix of salt and freshwater habitats acts as a natural filtration system to protect water quality. Topanga Lagoon and Creek also host some of the rarest fish and wildlife species in the area. Its beach is not only a popular place to sunbathe and pursue outdoor recreation activities, but also buffers local facilities from storm damage.
Once containing 30 acres of pristine wetlands, Topanga Lagoon has been whittled down to less than 1 acre due to long-term development patterns. By restoring Topanga Lagoon in a coordinated and proactive way, we can preserve this haven of unique biological, cultural and recreational resources, while improving existing public infrastructure. The Topanga Lagoon Restoration project provides an opportunity to enhance coastal access, expand recreation opportunities, and develop buffers for projected sea level rise.
Key Restoration Goals
The overarching goals of the restoration of Topanga Lagoon are to expand and restore the lagoon ecosystem; integrate public access, recreation, and visitor serving needs; and proactively address sea level rise, all the while protecting existing biological, cultural and recreational resources. Specific project objectives include:
-
Expand and restore the lagoon ecosystem to improve estuarine hydrologic functions, water quality, species and habitat diversity and protections for sensitive species.
-
Replace the aging Pacific Coast Highway (PCH) bridge to support lagoon restoration and recovery of endangered steelhead trout and tidewater goby.
-
Improve resilience of important structures and habitats to sea level rise and storm surge.
-
Enhance local beaches by nearshore placement of native soils, while maintaining the integrity of the surf break.
-
Establish a “Gateway Corner” at the NW corner of the intersection of PCH and Topanga Canyon Boulevard to provide coastal access and visitor services for the entire project area.
-
Integrate and improve recreational facilities, emergency services, and coastal access for the entire project area, including improvements for pedestrians, cyclists, and visitors with disabilities.
-
Minimize harm during construction: protect existing sensitive species, surf break and beach recreation.
Schedule
This project is in the planning phase. The Environmental Impact Report for the project was released in February of 2024 and is available for public review until April 12th, 2024. Design for the project is anticipated in 2024-2026, and construction is anticipated in 2027+
Project Alternatives
The project is considering one “no project” alternative, and three “build” alternatives that seek to address the challenges and threats to onsite biological and cultural resources and find ways to expand and enhance them. The “build alternatives” also seek to expand and improve coastal access, recreation, and visitor amenities, while proactively addressing sea level rise (SLR) and the related threats to coastal infrastructure and ecosystems.
What the Alternatives Have in Common
All three alternatives would replace the 79’ long Caltrans Pacific Coast Highway (PCH) bridge and replace it with one that is 460’ long, thereby allowing the expansion of the lagoon/creek habitat to 7-10 acres that will provide more refugia for endangered tidewater goby and steelhead trout. All alternatives provide ~ 1 acre of additional beach habitat and will identify the fate of the degrading Topanga Ranch Motel to determine if it will be removed or restored. Unified trail, parking, and emergency response systems would be developed for the entire project area. State Parks would create a new visitor hub at the Gateway Corner (NW corner of the intersection of PCH/Topanga Canyon Blvd.) where visitor services such as an interpretive pavilion, parking, restrooms, bus stop, picnic area, employee house and maintenance facility would be developed. Wastewater management options on State Park property would be improved and would include either a 1-mile sewer line connection along PCH to Los Angeles County Sanitation District facilities or would install advanced onsite wastewater treatment options onsite. Los Angeles County would relocate the lifeguard/restroom building and parking facilities further inland and at a higher elevation to protect them from SLR. A new helipad would be developed adjacent to the lifeguard building.
During restoration, earthwork will occur largely outside the edge of the riparian woodland to largely avoid impacts to wetted habitats. In-water work within Topanga Creek is anticipated to be limited to an ~ 0.33-acre area associated with removal of the existing PCH bridge. 166,000-256,000 cubic yards of native fill would be removed during restoration activities and is proposed to be placed off Topanga Beach between 15-25 feet depth for nearshore nourishment. Construction would take about 5-6 years to complete depending on the alternative and wastewater option chosen.
How the Alternatives Are Different
Alternative 1, No Project: No project occurs resulting in no restoration of the lagoon and adjacent open space areas. Species such as the endangered steelhead trout and tidewater goby would face potential local extirpation due to greater environmental stressors associated with SLR, a shrinking lagoon, and extreme weather events. The Topanga Ranch Motel would continue to degrade, and County beach facilities and associated natural resources would continue to be threatened by SLR.
Areas proposed for restoration/visitor services shown via hatching. Additional open space areas enhanced within the project boundary via removal of invasive plants & focused plantings.
Alternative 2, Maximize Lagoon: Will maximize lagoon/creek restoration by fully removing the Topanga Ranch Motel resulting in ~9.5 wetted acres, ~23 riparian/transitional upland acres restored and beach expansion to ~4.39 acres. No change to the PCH alignment occurs.
Alternative 3, Maximize Historic: Retains and restores most of the Ranch Motel (20 of 25 structures) for State Parks usage as either low cost overnight accommodation or a mix of park interpretive, office, employee housing, and maintenance uses. This will result in ~7.7 wetted acres, with ~23.7 riparian/transitional/upland acres restored and beach expansion to 4.42 acres. No change to the PCH alignment occurs.
Alternative 4, Maximize SLR Resiliency: Retains and restores a smaller portion of the Ranch Motel (15 of 25 structures) for State Parks usage as either low cost overnight accommodation or a mix of park interpretive, office, employee housing, and maintenance uses. This will result in ~7.6 wetted acres, with ~23.7 riparian/transitional upland acres restored and beach expansion to ~4.56 acres. The PCH is shifted north to maximize beach and associated facility retreat.
State Parks, project partners and project stakeholders may ultimately choose a hybrid or blend of these alternatives after hearing feedback from the landowners, regulatory agencies and the public during the environmental document public review period.
An overview of the project Build Alternatives
Vision for the Future
Imagine what a restored Topanga Lagoon and new and integrated development of visitor services could look like! Below are some visualizations of how the extent of lagoon and facilities would change under each project alternative.
Visualizations of the lagoon today and post-restoration for each Project Alternative. Credit: RCDSMM, 2024.
Project Partners & Stakeholders
The Topanga Lagoon Restoration Project area is managed on behalf of the public by the California Department of Parks and Recreation (State Parks), California Department of Transportation (CalTrans), and County of Los Angeles Department of Beaches and Harbors (Beaches and Harbors). The Resource Conservation District of the Santa Monica Mountains (RCDSMM) is the grant and project manager for the project in coordination with the public landowners. Funding for the project has been provided by the Wildlife Conservation Board, State Coastal Conservancy, the California Department of Fish and Wildlife and through the efforts of former Assemblymember Richard Bloom. Additional project stakeholders include a lengthy list of regulatory agencies, area universities and research institutions, environmental organizations, local stakeholders and the public.
