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The Los Angeles River Fish Passage & Habitat Structures Design Project


The Los Angeles River Fish Passage and Habitat Structures Design (LAR FPHS) Project is a multi-agency partnership effort funded by the State of California Wildlife Conservation Board (WCB) under a Proposition 68 Restoration Grant for Wildlife Corridors and Fish Passage Program. The Project is led by the Council for Watershed Health (CWH), City of Los Angeles, and Stillwater Sciences in coordination with other partners and government agencies, including the U.S. Bureau of Reclamation (USBOR), Southern California Coastal Water Research Project (SCCWRP), National Marine Fisheries Service (NMFS), U.S. Army Corps of Engineers (USACE), County of Los Angeles, California Department of Fish and Wildlife (CDFW), U.S. Fish and Wildlife Service (USFWS), Regional Water Quality Control Board (RWQCB), Arroyo Seco Foundation (ASF), and Friends of the Los Angeles River (FoLAR).

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Steelhead trout was once a common species in the LA River Watershed until the 1940's when Steelhead populations drastically decreased due to the impact of excessive recreational fishing and the presence of man-made physical structures and barriers.



It would take an estimated 2.7 days for an adult steelhead trout to travel 20 miles, from the mouth of the L.A. River in Long Beach, to the Fish Passage & Habitat Structure project site near Boyle Heights, Los Angeles.


A juvenile steelhead (credit: unknown) Among members of the salmon family, the Southern California steelhead trout ( Oncorhyncus mykiss), or simply steelhead, is the only species for which a thriving population was commonly found in coastal waters and within watersheds of Southern California, from Point Sal down to the U.S./Mexico border. Throughout this coastal region, large numbers of adult steelhead were swimming from the ocean into rivers and streams between winter and spring to migrate further upstream through coastal watersheds, including the Los Angeles River Watershed (LARW), and spawn in upper reaches of mountainous tributaries. After rearing in freshwater systems, juvenile steelhead reached maturity and many of them were able to migrate back to the ocean as adults to complete the life cycle. But in the early 20th century, the Southern California Steelhead population started to decrease abruptly due to the negative impacts of overfishing and urbanization, including constructions of dams, flood control structures, and other man-made barriers that precluded the natural passage of fish and their upstream (adults) and downstream (juveniles) migrations throughout urban coastal watersheds. The population abundance plummeted to such low numbers that the Southern California Steelhead distinct population segment (DPS) has been listed in the Endangered Species Act (ESA) since 1997. Similarly, steelhead was a common species in the LARW until the 1940s, before the population drastically decreased due to the impact of excessive recreational fishing pressure and the presence of man-made physical structures and barriers, in both the Los Angeles River mainstem and some of the upper tributaries. However, some of these upper tributaries are still home to isolated populations of rainbow trout, which is the non-anadromous life history form of O. mykiss. These populations can interbreed with steelhead, and either of these two life history forms can produce offspring that exhibit the alternate form (i.e., resident rainbow trout can produce anadromous progeny and vice-versa). These rainbow trout populations are considered as relicts of native coastal steelhead lineage that have adopted a resident life history in freshwater systems, with juveniles that do not migrate back to the ocean after rearing and adults that remain in freshwater systems until the next spawning occur. The LARW is considered an important region to support the viability of the remaining populations of Southern California Steelhead due to its key role in potentially maintaining resident rainbow trout populations of coastal steelhead lineage in its upper tributaries. In fact, recommended recovery actions for the LARW listed in the NMFS’s Southern California Steelhead Recovery Plan, issued in 2012, include habitat restoration, remediation of passage barriers, and other actions that address major stressors and limiting factors for the Southern California Steelhead DPS.


The main objective of the LAR FPHS Project is to conduct science-based research and design (Basis of Design Report to 60% design drawings, CEQA, and initial permitting) of fish passage and habitat structures that address limiting factors for steelhead and other native fish within a 4.8 mile section of the Los Angeles River in the downtown city area. The Project provides opportunities to address watershed-wide data gaps. In turn, this information can be used to fill these gaps and to support future projects aimed to enhance steelhead recovery throughout the LARW, and to identify other potential suitable sites for fish passage projects across the Los Angeles River and its upper tributaries.


The LAR FPHS Project started in January 2020, and is planned for completion in December 2021.


Why are we doing this project? The Council for Watershed Health (CWH), City of Los Angeles, and Stillwater Sciences are leading the LAR FPHS project in partnership with USBOR, SCCWRP, NMFS, USACE, County of Los Angeles, CDFW, USFWS, RWQCB, ASF, and FoLAR. The city has adopted sustainability and biodiversity plans to bring back native species, including steelhead and other native fish among many other species, with an ultimate goal of improving connections between people and nature. This project is intended to create steelhead fish passage in the LA River as a migration corridor to the upper tributaries of the LARW spawning grounds, and is a pilot project that can be replicated in other concrete-lined channels to provide fish passage and habitat structures for migrating fish. Watershed scientists are working to address study questions focused on watershed-wide limiting factors to steelhead recovery. This project provides an opportunity to align with related USACE, City and County restoration projects, scientific studies, and ongoing watershed and LA River monitoring plans and efforts. These include, but are not limited to, the following project objectives: 1. To implement key features of the Congressional Authorization of the LA River Ecosystem Restoration Project, Alternative 20 Integrated Feasibility Report. 2. To implement conceptual USACE Arroyo Seco Ecosystem Restoration Watershed Study recommendations of fish passage, barrier removal, stream naturalization, and fish habitat improvements to support multiple life stages of rainbow and steelhead trout and re-establishment of resident trout populations. 3. To improve conditions for other native fish in the LARW and upper tributaries, including Santa Ana sucker, Arroyo chub, unarmored three-spine stickleback, speckled dace, Pacific lamprey, and other aquatic species and wildlife. 4. To implement adopted plans, policies, and recommendations of federal, state, regional, and local agencies, including NMFS’s Southern Steelhead Recovery Plan, City of LA’s LA River Revitalization Master Plan, Greater LA River Integrated Regional Water Management Plan, County LA River Master Plan, LA Mayor’s Sustainability Plan, LA Biodiversity Plan, and others. 5. To enhance ecological connectivity between in- and off-channel areas to maximize the urban biodiversity and ecosystem benefits (environmental and socio-economic) of the project. Will we really see steelhead in the LA River again? Yes. If effective fish passage design and conditions are implemented, steelhead will be able to migrate to upper tributaries of the LARW and ultimately complete their life cycle. Steelhead thrive in cool, clean, well-oxygenated water. The LARW’s water quality, temperature, vegetation (providing shade and natural cleansing of flows), and stream conditions (e.g., dissolved oxygen levels, velocity, sediment load, etc.) will need to improve to support total maximum daily loads (TMDLs), water quality thresholds set by the RWQCB under the Clean Water Act, as well as steelhead suitability requirements. A healthy ecological riverine and aquatic system in the LA River will address the needs of both fish populations and local communities. Many Angelenos have expressed interest in a clean LA River, with prospects of recreation, enjoyment, and fishing. But before fishing for endangered steelhead can be feasible, the species must first be delisted from the ESA, in which the Steelhead Southern California distinct population segment (DPS) has been listed since 1997. By meeting the needs of native fish species in the LA River, this pilot project promotes species recovery as a first priority, with numerous multiple benefits for Angelenos in perpetuity. Cost

How is the “project design” being funded?

The Wildlife Conservation Board has funded this project under a State of California Prop. 68 Fish Passage grant (WC-1922DC) in the amount of $1.356M. The City and other partners, including Stillwater Sciences, SCCWRP, ASF, and FoLAR, are providing in-kind services as matching funds for the project. Future phases of the project will include 100% final design, permitting, and construction.

How will “implementation” of the project be funded?

The full cost to implement the project is currently unknown. The project proponents will work with the associated agencies and additional partners to identify funding to fully implement the project.

Who is responsible for operations and maintenance?

The project is being designed to be self-cleaning by mimicking natural stream morphology, with natural flushing of sediment through pool-riffle-run sequences. Habitat structures would be anchored in place to maintain channel stability and protection of existing infrastructures. Flood-related requirements must be met in order for the project to be constructed. The City, County, and USACE are discussing operations and maintenance roles and responsibilities for the project. Maintenance responsibilities would be similar to what they are now, which is minimal in this concrete-lined reach of the channel. However, future project maintenance costs, if any, would be funded through a cooperative agreement with the project partners.


What type of monitoring is required?

Monitoring includes assessment of structural stability of the structures, biological surveys (specific to steelhead and other native fish as well as invasive species), and physical habitat conditions.

Water Supply Priorities

Does the project impact water supplies?

No. The LAR FPHS project is consistent with the California State Water Resources Control Board (SWRCB)’s LA River Environmental Flows Study (EFS) that is currently underway. As project partner, SCCWRP is working on the modeling and steelhead/rainbow trout species criteria for the LA River in collaboration with Stillwater Sciences. Steelhead are one of many target species considered in SCCWRP’s hydrologic and hydraulic modeling for the LA River. Since the LAR FPHS project is focused on migratory periods, meaning when steelhead move at the tail-end of a winter storm, no additional water is needed to support migration. LA Department of Water and Power, among other water utilities, is involved in the study to address integrated water management objectives (water quality, water reuse, recycling, and other water supply/management objectives). The design does include low-flow conditions for fish to move upstream and downstream. These flows are also consistent with the SWRCB LA River EFS.

How fast do steelhead swim? Migration rates reported for adult steelhead in rivers are highly variable, ranging from less than 0.6 miles per day (mi/d) to more than 25 mi/d (Keefer et al. 2004, Salinger and Anderson 2006, English et al. 2006, Jepsen et al. 2012). In the absence of data on southern steelhead behavior, migration rates for steelhead in the LA River are assumed to be similar to those of steelhead migrating in naturally flowing rivers, like those measured in British Columbia, Canada (English et al. 2006). For such rivers, steelhead migration rate averaged 7.3 mi/d. Based on this average migration rate, when applied to adult steelhead in the LA River, it is expected that adult steelhead would take 2.7 days on average to reach the LAR FPHS project reach 20 miles (mi) upstream from the ocean and four days to reach perennial habitat in the central Arroyo Seco 30.5 mi upstream from the ocean. According to steelhead migration rate data from English et al. (2006), steelhead would take a maximum of five days and a minimum of two days to reach the LAR FPHS project site. Similarly, steelhead would take a maximum of eight days and a minimum of three days to reach perennially-flowing, soft-bottom habitat in the central Arroyo Seco. It remains uncertain whether the duration of a typical storm flow event is long enough for steelhead to reach these locations in a single event, or if multiple storm events are needed.


For more information please reach out to the LAR FPHS Project Manager, Andrea Dell’Apa or 213-229-9945 - ext.5.



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Council for Watershed Health

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Council for Watershed Health (CWH) is a tax-exempt 501(c)3 organization. Contributions to CWH are tax-deductible to the fullest extent of the law.

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