The Arroyo Seco Foundation
The Arroyo Seco Foundation (ASF) was founded by Charles Lummis more than one hundred years ago to preserve and promote the Arroyo Seco, one of Southern California's greatest natural treasures. The Arroyo Seco is a spectacular stream and canyon that runs from high in the front range of the San Gabriel Mountains all the way to downtown Los Angeles.
After a lapse of many decades, the Arroyo Seco Foundation was revived in 1989 to continue that vision. Since then we have planted several thousand native trees in the Arroyo, participated in and led major Arroyo planning efforts, educated the public about the riches of the Arroyo, and most importantly worked to restore and enhance the natural splendor of the Arroyo for future generations.
ASF has brought over $30 million in funding into the Arroyo Seco Watershed. Some of the major projects have included the low-flow stream restoration program in the Lower Arroyo in the 1990s, the Central Arryo Stream Restoration Program, which brought back native fish to the Arroyo, the Watershed Coordination Program, and the Arroyo Seco Canyon Project.
ASF is a community-based 501(c)(3) nonprofit organization. We advocate an integrated, harmonious approach to watershed and flood management, water conservation, habitat enhancement, and the expansion of recreational opportunities. Through action projects, recreation, and environmental awareness activities, ASF strives to involve the residents and organizations in our region in this tremendous enterprise. As a member of the California ReLeaf tree-planting network, ASF works to reforest the Arroyo Seco, the San Gabriel Mountains and the neighboring urban landscape with native shrubs and trees.
The activities of the Arroyo Seco Foundation enable local residents and businesses to become directly involved in the restoration of the Arroyo Seco and in the recreational and environmental opportunities available.
Major Programs for 2022 include:
Restoring Trout to the Arroyo
ASF is workingn to restore conditions for native fish in the Los Angeles River system. We are working with a great group of agencies and organiations that is studying how to alter the LA River flood channel to accomodate steelhead in downtown Los Angeles near the confluence with the Arroyoo. Check out our neat video about that effort — Against the Current.
We are also working to improve conditions for Rainbow Trout in the upper mountain watershed of the Arroyo Seco. We were very pleased to learn that the California Department of Fish and Wildlife has augmented the population of native trout in the Arroyo will 469 Rainbow Trout from the nearby West Forkk of the San Gabriel River as part of a rescue program following the 2020 Bobcat fire. ASF has been sending an erstwhile team of Trout Scouts into the upper waterhed to survey for the fish and to document stream and habitat conditions to expand our trout restoration program. Read the LA Times account which appeared on June 17, 2021.
Saving LA's Streams
The North Branch of the Arroyo Seco drains all of Highland Park and flows into the Arroyo Seco at the historic Sycamore Grove Park. Regretably, the stream was put into a 9'x9' box culvert and buried beneath Highland Park and the park in 1939. Storm drains like that pick up pollution throughout their drainage area and carry it through the concrete channel to the Arroyo, the Los Angeles River, and eventually to the Pacific Ocean. The Los Angeles Bureau of Sanitation is now conducting a program that will transfer the dry-weather flow of the North Branch tributary into LA's main sewer system and take it all the way to the Hyperion Treatment Plant near LAX.
ASF's goal is to promote nature-based solutions and to restore as much as possible of the natural hydology of the Arroyo Seco watershed, so we have organized a lot of community concern in Northeast LA to the Bureau of Sanitation's "stream to sewer" program. To the Bureau of Sanitation, it's just a plumbing project to their sewer, but to us the North Branch is a key part of the lifeline for the people, habitat and wildlife of the Arroyo Seco.
Save Hahamongna
ASF has joined together with the Pasadena Audubon Society and other community groups and advocates to minimize the devastating impacts of LA County Flood Control District's sediment excavation and trucking program in Hahamongna Watershed Park. We are working with the Hahamongna Accountability Project to ensure that the County complies with all their commitments and regulatory requirements for the project. Habitat restoration, dangerous air pollution and the long-term footprint of the County's maintenance area are among the chief concerns now being addressed through community education and outreach and two separate lawsuits.
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Our work is made possible by the generous contributions of time and other resources by community members. The Stream Team is ASF'a volunteer corps. Members participate in clean-ups, tree-planting programs, habitat assessments, invasive species removals and a variety of other activities.
Arroyo Seco News and Education
ASF has an active social media presence with two Facebook sites, ASF and Hahamongna Native Plant Nursery, an Instagram site and a Twitter Account. These forums offer up-to-date new and informative coverage of important environmental issues and happenings that allow Arroyo afficionados to stay up-to-date and spread the work about important Arroyo issues, projects and events.
Monitoring Arroyo Planning Efforts
A multitude of planning efforts are now underway to upgrade and transform the Arroyo. These include the development of a master plan for the Angeles National Forest, Pasadena's Arroyo Seco EIR, South Pasadena developments, Debs Park, Confluence Park planning and other efforts.
Tours and Educational Events
An important part of ASF's mission is to educate the public about water managment in the watershed. ASF staff and volunteers lead informative walking tours of the Arroyo Seco, as well as outreach to student groups. Topics include water resources, habitat, culture and history of the Arroyo Seco.
Quarterly Meetings
For several years ASF has presented a quarterly meeting at the Donald Wright Auditorium of the Pasadena Central Library to allow members and the general public to be kept up to date on the latest Arroyo issues and projects of the Foundation. This program had to be cancelled due to the pandemic, but we have responded with quite an impressive series of online meetings called Arroyo Currents that are available to the public on Youtube.
Recently Completed
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Berkshire Creek drains a small watershed around La Canada High School before it comes into the west side of the Hahamongna basin above Devil's Gate Dam. ASF co-sponsored this program along with the City of Pasadena to restore a more natural stream here. Past flood flows through a large culvert have degraded the stream and habitat conditions. The project, which was completed in 2020, repaired the erosion and established a more sustainable stream zone. It's a great model for other Arroyo restoration projects.
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The Pasadena Public Works Department has recently (Spring, 2021) completed an important restoration program in the Lower Arroyo, a wonderful area from the Colorado Street Bride down to the South Pasadena city limit. ASF was pleased to promote the project and win support for it, but disappointed that a significant number of inappropriate Eucalyptus and Canary Island Pine trees that detract from the habitat and wildlife values of the Arroyo were not replaced.
Our Mission
"To preserve and enhance the Arroyo Seco River and its watershed through education, community involvement, improvement projects, and advocacy."
Hahamongna Native Plant Nursery

ASF has established this community-based nursery to produce native plants for habitat restoration projects and to beautify local yards, businesses and public facilities. HNNP is part of a movement to transform the landscape of Southern California through a return to the spectacular plants that are ideally suited to our climate and condiations and that foster biodiversity. The nursery is fueled by volunteer energy, so we encourage you to get involved too by helping grow plants and by buying some from your yard or garden.
Want to help
restore the Arroyo?
Join the Arroyo Seco Stream Team!

ASF is a proud member of the California Releaf Network
CASO
CASO, the Council of Arroyo Seco Organizations, has become a key network for organizations working to improve the Arroyo Seco from the mountains to Downtown Los Angeles. For more information. CASO organizations meet each quarterly to exchange information aout Arroyo projects and to plan and work togehter for the future. ASF provides organizational support to this vital network.
CASA
The governmental agencies which manage the Arroyo Seco have been meeting together regularly for fifteen years now to discuss common goals and projects affecting this unique region. This important network is called CASA, the Council of Arroyo Seco Agencies.
Arroyo Seco Foundation, 570 W. Avenue 26 #450, Los Angeles, CA 90065-1011
PO Box 91622, Pasadena, CA 91109-1622 (323) 405-7326
info@arroyoseco.org