Arroyo Seco Via - Ride the Arroyo!

Get ready to ride on the biggest and funnest Arroyo cycling event ever! On Saturday, September 28 Arroyo Seco Via will link up downtown Los Angeles with Pasadena and the San Gabriel Valley in a fun and festive bike ride to promote the implementation of a protected bike path for commuting and recreational use. Building on the excitement of CicLAvia, riders will depart from Hahamongna Watershed Park, nestled at the foot of the San Gabriel Mountains in Pasadena, and proceed to the Los Angeles State Historic Park at the Cornfields near downtown Los Angeles. It's an eleven mile route each way, perfect for riders of every skill level.

At Hahamongna riders will share in the 20th Anniversary of Hahamongna Watershed Park, and at Los Angeles State Historic Park they will join up with a fantastic Los Angele River Rally to support the best restoration plan from the US Army Corps of Engineers LA River Study.

ASF Opposes New Bridge in Lower Arroyo Park

Pasadena is considering construction of a new bridge across the flood channel in Lower Arroyo Park. The bridge would be used for the rehabilitation of the La Loma Bridge, but then Pasadena plans to leave it as a permanent addition to the park.

For many decades local residents have been clamoring for the removal of the flood channel and the restoration of a living stream in this stretch of the Arroyo. The flood channel has long been an annoying obstacle in Lower Arroyo Park, so while we support access, trail continuity and circulation throughout the Arroyo, we believe that Pasadena staff should be looking at ways to remove the flood channel itself before investing in new, permanent infrastructure. The US Army Corps of Engineers Arroyo Ecosystem Study is now considering just such a major stream restoration in Pasadena's Lower Arroyo. Let's not undermine that very promising opportunity.

Here is the letter ASF sent to Pasadena's historical consultant on the project: No Bridge Now

Let's Celebrate the 20th Anniversary of Hahamongna Watershed Park

This fall will mark twenty years since LA County's Oak Grove Park was transformed into Pasadena's Hahamongna Watershed Park. It was a bold step toward integrated, sustainable management of one of our region's most valuable assets, fostered by visionaries like Tom Underbrink, Ernie Messner, Vera Rocha, Tim Brick, Rick Cole, Charles Thomas and Bob Takata. The Arroyo Seco Foundation is working with the City of Pasadena to celebrate the watershed park and the people who made it possible on September 28, 2013.

If you would like to help organize this celebration and spread the word, please contact Tim Brick at

Army Corps Study Promises Ecosystem Restoration for the Arroyo Seco

ASF and local agencies, including the Couty of Los Angeles, Pasadena, La Canada Flintridge, South Pasadena, Los Angeles and the Raymond Basin Management Board are now working with the US Army Corps of Engineers to develop the projects that will restore the Arroyo Seco ecosystem as part of the Corps Arroyo Seco Watershed Ecosystem Restoration Study.

Here are the site that the Corps has its eyes on for potential projects:

  • Hahamongna Area
  • Flint Wash
  • 210 Freeway near Oak Grove
  • Brookside Area
  • Lower Arroyo Park
  • South Pasadena Island
  • Arroyo Seco through Los Angeles
  • Sycamore Grove Park
  • Rainbow Canyon

Learn More about the Corps' Sites and Objectives

Welcome to the Arroyo Seco Calendar!

Your guide to special events related to the Arroyo Seco, the Los Angeles River,
the San Gabriel Mountains, and key environmental topics in our region.

6:30 PM


This is the always-informative gathering of community groups and activists working together to better the Arroyo Seco and its communities.

9:00 AM


Get ready to ride and celebrate the Arroyo Seco.

News of the Arroyo

Click on the title link to read the entire story.

Environmental documents for proposed delta project criticized

July 18, 2013 — Federal agencies are raising substantial criticisms of the environmental documents for the Bay Delta Conservation Plan and the facilities related to it.

Morris Dam upgrades improve L.A. County's water preservation, management efforts

July 25, 2013 — Originally built during the Depression by the Pasadena Water Department, Morris Dam gets upgrades from the County Department of Public Works to bring it into the 21st Century.

L.A. River advocates wait for watershed Army Corps study

July 24, 2013 — The Corps is putting the finishing touches on a much-anticipated, much-delayed feasibility study focusing on an 11-mile stretch of the river between Union Station and Griffith Park. The study, expected to be released Aug. 30, will weigh three ambitious plans aimed at restoring the river's natural ecosystem and improving public access to its banks.

L.A. County liable for storm-water pollution, court rules

August 8, 2013 — A federal appeals court dealt Los Angeles County a blow on Thursday in a long-running lawsuit over storm-water pollution when it issued an opinion that the county is liable for excessively high levels.