Army Corps Arroyo Seco Ecosystem Study

The Arroyo Seco through Los Angeles

Los Angeles Arroyo Seco (5.5 miles in length): The Arroyo Seco stream travels through a stretch lined on one side by South Pasadena and on the other by Los Angeles; at the York Blvd. Bridge, the Arroyo River proceeds through a narrow, highly urbanized canyon lined with a series of Los Angeles Parks down to the confluence with the Los Angeles River.

South Pasadena/Los Angeles Interface

  • As the Arroyo stream reaches the transition zone between Pasadena, South Pasadena and Los Angeles, there are excellent opportunities for restoring a naturalized stream with riparian habitat and wetlands. Near San Pasqual Drive, the Arroyo Seco stream is surrounded by San Pasqual Park, a Los Angeles city park on the west side, and Sycamore Park, a South Pasadena park on the east. These parks could be outstanding examples of Arroyo River Parks, providing stream restoration and habitat enhancements as well as water quality improvements and stormwater capture.

  • Just to the south of the Arroyo Seco Parkway (aka Pasadena Freeway), the stream turns westward and is bordered by a large island of land that could be moulded into the river with terraces and habitat improvements. On the south side of the Arroyo stream is the golf course, which will soon accommodate a pedestrian and bicycle trail, and the existing South Pasadena Nature Park that could be linked to the streambed. The island is owned by the City of Los Angeles, while the other side of the stream is in South Pasadena.

Arroyo Seco River Parks through the City of Los Angeles

Project Elements

  • The Arroyo Seco is lined with parks from the very top near the famous Mt. Wilson Observatory to about 2 miles upstream from the Confluence with the Los Angeles River. Some of these parks, up until the Los Angeles city limit, integrate the river and appropriate riparian habitat with recreational opportunities. The Arroyo Seco River Parks system through the City of Los Angeles will complete the stream side trail system for the entire 22 mile Arroyo Seco. The implementation of river themed parks, complete with river access, stormwater capture, riparian and wetland habitat, and water quality improvements will maintain traditional park uses while enhancing recreational opportunities and environmental awareness.

North Branch - Sycamore Grove Park

  • A major tributary of the Arroyo Seco flows across Highland Park from the San Rafael Hills and enters the Arroyo Seco stream at Sycamore Grove Park. The North Branch stream used to flow gently through Sycamore Grove Park but many years ago the stream was put into a major pipe that now runs beneath the park. There is excellent potential for daylighting that stream and restoring a rich riparian zone in the park.

Lower Arroyo Linkages

  • The Lower Arroyo Linkages project is a series of integrated transportation, water resource, and habitat enhancement projects along the lower Arroyo Seco river corridor that will improve public safety, transportation, economic vitality, recreation, water quality, and ecosystem health in neighborhoods in the City of Los Angeles, including Highland Park, Mt. Washington, Garvanza, Hermon, Montecito Heights, and Cypress Park. In the lower reaches of the watershed, this project is a culmination of years of grassroots planning efforts focusing on the spine of the Arroyo Seco Watershed: the Arroyo Seco and the Arroyo Seco Parkway (a National Scenic Byway Corridor).

Integration with the LA River Ecosystem Restoration

  • The US Army Corps of Engineers is completing an Ecosystem Restoration Program on the Los Angeles River through the "ARBOR" reach from Glendale narrows to downtown Los Angeles. This program includes the Arroyo Seco Confluence from the Los Angeles River up half a mile of the Arroyo Seco River. Major restoration of The Confluence area will include removal of concrete, expanding the flood prone width of the river, establishment of wetland and riparian habitat, and trail connectivity. The Arroyo Seco is presented with the amazing fortune of being included in two USACE ecosystem programs. This unique opportunity will allow for a comprehensive ecosystem enhancement and massive river restoration throughout the urban portion of the river. The two programs should coordinate and cooperate throughout their life spans to provide maximum benefit to habitat, stream restoration, water resources, recreation and quality of life.