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Tujunga Wash Greenway and Stream Restoration Project

Landscape Performance Benefits

Environmental

  • Infiltrates up to 118 million gallons of water from the concrete Tujunga Wash flood channel each year, recharging the San Fernando groundwater basin.

Social

  • Increases the ratio of park space per 1,000 residents by 21% to 1.23 acres.

Economic

  • Reduces potential landscape water use by 70-80% by using all native plants. This saves $8,000-$20,000 per year in irrigation water costs.

At a Glance

  • Designer

    Mountains Recreation & Conservation Authority

  • Project Type

    Park/Open space
    Recreational trail
    Stormwater management facility

  • Former Land Use

    Greyfield

  • Location

    Coldwater Canyon Ave and Oxnard Blvd
    Los Angeles, California 91606

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  • Climate Zone

    Hot-summer Mediterranean

  • Size

    1.2 miles (~16 acres)

  • Budget

    $7 million (landscape) of a $10 million total budget

  • Completion Date

    2007

Rivers and streams in Los Angeles are being rediscovered decades after they were turned into concrete ditches to speed floodwater out to sea in response to several catastrophic floods. The Tujunga Wash Greenway and Stream Restoration Project is a prototype to reintroduce riparian habitat throughout the city. A tributary of the Los Angeles river, the Tujunga Wash is a 13-mile urban stream. Prior to channelization of the wash for flood control in the 1950s, the area was an important zone for groundwater recharge. The 1.2-mile Greenway project transformed the once inaccessible right-of-way along the concrete box channel into an ecologically productive greenway and riparian system 10 feet above the channel bottom. A rich palette of native plantings create wildlife habitat along both banks of the concrete wash. This verdant oasis offers a tranquil experience for visitors using the recreational pathways and seating areas, providing a strong contrast from the urban experience in the immediate vicinity.

  • The 1.2-mile long, 50- to 60-ft wide Greenway creates 15 acres of riparian habitat through Los Angeles’ urban fabric, replacing a formerly barren right of way. Urban habitat patches such as this, directly impact species conservation and survival, as well as residents’ access to wildlife.
  • Water to feed the re-created stream environment is diverted from 2 miles upstream of the greenway headworks through a gravity-fed pipe.
  • 10-ft wide trails line both sides of the concrete channel. On the western bank, 85% of the trails are permeable, made of decomposed granite. These 2.4 miles of off-street, multi-use trails provide opportunities for recreation in a car-dominated neighborhood and connect to the regional trail network and bike routes.
  • The site was divided into 8 geomorphic and ecological areas, with specific plant palettes for each area. 1,100 trees and 18,000 shrubs and vines were planted along either side of the wash – all 100% California native. Trees include walnut, laurel, ash, cottonwood, live oak, and willow species. 
  • Interpretive signage educates the public about the Greenway’s water filtration and infiltration benefits.

Challenge

The Greenway was part of the Los Angeles River and Tujunga Wash Master Plan. While the initial goal was to create habitat, the project objectives quickly grew to include restoring some of the wash’s natural functions along the side of the flood control channel. Challenges during the design process included determining a strategy to restore natural stream function despite the environmental damage inflicted during channelization, and addressing community concerns given the close proximity of private homes to the channel. These concerns included liability and safety issues, such as the lack of visibility due to overgrown shrubs, which prolonged the permitting process.

Solution

Some of the wash’s natural functions were restored by creating a naturalized streambed, fed by an upstream diversion of up to 325,000 gallons of water per day from the flood control channel. This allows for natural filtration and infiltration after rain events. Community and safety concerns were addressed through public outreach and strategic timing of the construction to coincide with the dry season (April 15 - October 15). Five community meetings were held to get input from the neighborhood. To address concerns regarding vagrancy and vandalism, an 8-foot high fence was installed along some properties, as well as a new iron gateway that both marks the entrance to the Greenway and can be locked as a safety precaution. To increase visibility and reduce perceived threats, the maintenance team periodically limbs-up overgrown shrubs and trees.

  • Ongoing education and outreach are necessary since the stream changes seasonally, and users need to understand what to expect regarding the look and odor of the natural system.
  • In man-made streambeds, it is imperative to be able to remove sediment efficiently. To maintain intended infiltration rates, the top layer of silt needs to be periodically removed and the soil scored.
  • The initial goal of this project was to create habitat in an urban settting. The wider impacts of the streambed project and its ability to influence and catalyze subsequent projects were not foreseen. Had the greenway been considered as a prototype, formal evaluation and data collection procedures could have been established, which would help to measure impact and improve future designs. 

  • Real-time environmental monitoring is necessary for projects like this. Without any data, it is difficult to make habitat management decisions or to optimize the hydrological performance.

Project Team

Project Partners: Los Angeles County Flood Control District, Mountains Recreation and Conservation Authority, Los Angeles County Department of Public Works
Lead Agency and Designer: Mountains Recreation and Conservation Authority, Santa Monica Mountains Conservancy
Engineering: Los Angeles County Department of Public Works Flood Control District
Construction Management: Mountains Recreation and Conservation Authority, Los Angeles County Flood Control District
Construction: Los Angeles Conservation Corps, Powell Construction, Terra Form, W. A. Rasic Construction Company

Role of the Landscape Architect

The Mountains Recreation and Conservation Authority initiated the project with the Los Angeles County Department of Public Works, gathered funding from a variety of local and state sources, designed the landscape, created and bid on construction documents, installed the project, and continues to oversee the on-going monitoring and maintenance.

Case Study Prepared By

Research Fellow: Alexander Robinson, Assistant Professor, University of Southern California
Research Fellow: Barry Lehrman, Assistant Professor, Cal Poly Pomona
Research Assistant: H. Myvonwynn Hopton, MLA Candidate, University of Southern California
Research Assistant: Mallory Piazzola, MLA Candidate, Cal Poly Pomona
March 2013

Topics

Water conservation, Other water, Recreational & social value, Educational signage, Native Plants, Permeable paving, Trail, Trees, Active living

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