Santa Anita Creek

Santa Anita Creek
Name	Santa Anita Creek
Location	Los Angeles County, California, San Gabriel Mountains
Country	United States
State	California
Length	10.0
Source	San Gabriel Mountains
Mouth	Rio Hondo

Santa Anita Creek Santa Anita Creek is a perennial tributary in Los Angeles County, California originating in the San Gabriel Mountains and flowing through Arcadia, California, Monrovia, California, and Irwindale, California to join the Rio Hondo and eventually contribute to the Los Angeles River. The creek passes through multiple municipal, federal and recreational jurisdictions including Santa Anita Canyon, Angeles National Forest, Santa Anita Dam, and the Santa Anita Racetrack corridor, influencing regional infrastructure, flood control, and habitat connectivity. Key stakeholders include the U.S. Army Corps of Engineers, California Department of Water Resources, local water districts like the Metropolitan Water District of Southern California, and civic entities of Los Angeles County.

Course and Description

Santa Anita Creek rises on the south slopes of the San Gabriel Mountains near Mount Wilson and descends through steep canyons toward the San Gabriel Valley. The creek's upper reach flows within the Angeles National Forest and crosses historic routes such as the Santa Anita Canyon Road before being impounded at Santa Anita Dam creating a regulated flow into the alluvial fan plain near Monrovia and Arcadia. In the lowland the channel is partially channelized with concrete-lined sections adjacent to Santa Anita Park, industrial zones in Irwindale, and transportation corridors like the Foothill Freeway (Interstate 210) and California State Route 39. Tributaries and side canyons include streams draining from features near San Gabriel Peak, Baldy Bowl, and other peaks in the Angeles Crest.

Watershed and Hydrology

The Santa Anita Creek watershed is a portion of the larger Los Angeles River basin and lies within the jurisdictional boundaries of Los Angeles County Flood Control District and federal agencies including the U.S. Geological Survey. The watershed receives Mediterranean-climate precipitation driven by Pacific frontal systems and orographic lift over the San Gabriel Mountains, resulting in episodic high-flow events tied to atmospheric rivers and post-fire runoff after events such as the Station Fire. Flow regimes are influenced by snowmelt from higher elevations near Mt. Baldy during anomalous winters, regulated releases from Santa Anita Dam, and groundwater exchange with the San Gabriel Valley groundwater basin managed by entities like the Main San Gabriel Basin Watermaster. Monitoring is conducted by the USGS, California State Water Resources Control Board, and regional flood control authorities.

Ecology and Wildlife

Riparian corridors along the creek support native southern California flora including stands of coast live oak, California sycamore, southern willow scrub, and chaparral species common to the Mediterranean forests, woodlands, and scrub ecoregion. Fauna recorded in the corridor include California quail, coyote, bobcat, California spotted owl in upper canyons, amphibians such as Pacific treefrog, and native fish historically including southern steelhead relatives and species adapted to intermittent streams. The creek provides habitat connectivity between the Angeles National Forest and urban green spaces such as Monrovia Canyon Park and Santa Anita Recreational Center, facilitating dispersal for species affected by urban fragmentation and invasive species pressures like Arundo donax and Tamarix ramosissima.

History and Human Use

Indigenous peoples of the region, notably the Tongva (also known as Gabrielino), inhabited the Santa Anita Canyon and utilized the creek for resources along routes later traversed by explorers and settlers including those tied to Mission San Gabriel Arcángel and early Californio land grants like Rancho Santa Anita. The watershed saw increased alteration during the 19th and 20th centuries with infrastructure projects by Los Angeles County, flood control measures after storms like those prompting the Los Angeles Flood of 1938, and construction of facilities such as Santa Anita Dam by the U.S. Army Corps of Engineers. The area also supported orchards, rail lines alongside the Santa Fe Railroad and later recreational developments including the Santa Anita Racetrack, reflecting broader patterns in Southern California urbanization.

Recreation and Parks

The upper creek corridor within the Angeles National Forest provides hiking, camping, and equestrian access via trailheads that connect to systems managed by the U.S. Forest Service and local park agencies such as Los Angeles County Department of Parks and Recreation. Notable destinations and trail networks link to San Gabriel Mountains National Monument, Monrovia Canyon Park, and regional open-space areas administered by entities like the Santa Monica Mountains Conservancy and local conservancies. Urban segments adjoin community parks, wetlands restoration sites, and interpretive facilities supported by nonprofit organizations including the Arroyo Seco Foundation and local historical societies.

Environmental Issues and Conservation

Challenges in the Santa Anita Creek corridor include flood risk managed through structural controls by the U.S. Army Corps of Engineers and Los Angeles County Flood Control District, water quality concerns overseen by the California Regional Water Quality Control Board, sedimentation and debris flows exacerbated by wildfires such as the Station Fire, and ecological degradation from invasive plants like Arundo donax. Conservation responses involve riparian restoration, native revegetation projects supported by the National Fish and Wildlife Foundation and local land trusts, watershed planning coordinated with the Metropolitan Water District of Southern California and Main San Gabriel Basin Watermaster, and community-based stewardship driven by organizations including the San Gabriel Mountains Forever partnership and municipal conservation programs.

Category:Rivers of Los Angeles County, California Category:San Gabriel Mountains