page_title: Oso Creek
section_title: Course
hierarchical_section_title: Oso Creek / Course
caption_attribution_description: English: Map of the Oso Creek sub-basin's location in the San Juan Creek watershed, California
context_page_description: Oso Creek is an approximately 13.5-mile tributary of Arroyo Trabuco in southern Orange County in the U.S. state of California. Draining about 20 square miles in a region north of the San Joaquin Hills and south of the Santa Ana Mountains, the creek is Trabuco Creek's largest tributary, and is part of the San Juan Creek drainage basin. Beginning in the foothills of the Santa Ana Mountains near the city of Mission Viejo, the creek is dammed twice to form Upper Oso Reservoir and Lake Mission Viejo. The creek is channelized and polluted along much of its length.
  "Oso", meaning bear in the Spanish language, was likely the name given to the creek by Spanish conquistadors. Up to the 1970s, the Oso Creek watershed was mostly undeveloped and the creek ephemeral. The watershed lies close to two major wilderness areas - Aliso and Wood Canyons Wilderness Park to the southwest and O'Neill Regional Park to the west, on Trabuco Creek - but has no major parks within its boundaries. Interstate 5 parallels the creek for over half of its length.
context_section_description: The original headwaters of Oso Creek were in a small canyon in the south-central part of the Santa Ana Mountains. A dam was built across this canyon, flooding it to create Upper Oso Reservoir, which now forms the headwaters of the creek, fed by three small seasonal streams. After leaving the reservoir, Oso Creek crosses under California State Route 241 and for the next mile (1.6 km) of its course, it flows through a narrow riparian corridor surrounded by residential areas in the city of Mission Viejo. The creek enters an underground culvert, bends east and south, and enters Lake Mission Viejo, 12 miles (19 km) from the mouth.
  Downstream of the artificial lake, Oso Creek flows through a golf course, then after flowing through another narrow canyon, receives an unnamed tributary from the left, 10.5 miles (16.9 km) from the mouth. It then bends slightly to flow southwest and enters a culvert under Marguerite Parkway, emptying into another golf course, 8 miles (13 km) from the mouth. The creek then crosses under Interstate 5 and flows between the highway and Camino Capistrano through a series of freshwater marshes. The La Paz Channel, its largest tributary, joins here on the right. It passes the Galivan Basin, which functions to capture floodwaters from Oso Creek, on the right bank, and receives from the right a second unnamed tributary, 7.5 miles (12.1 km) from the mouth. This tributary actually flows through the Galivan Basin before meeting Oso Creek.
  The creek then bends southwest around several shopping centers near the convergence of Interstate 5 and California State Route 73, within the city limits of Laguna Niguel. Near this area, Oso Creek enters a concrete flood control channel with sloping sides, 5 miles (8.0 km) from the mouth. It then flows through a riprap lined channel before entering a concrete box culvert, which runs south under the state route. The creek then spills out into a natural channel, 1.2 miles (1.9 km) from the mouth, which it has incised to depths of 50 feet (15 m) or more, as the interstate bends southeast. Flowing through an agricultural area, the creek bends east to join Trabuco Creek inside San Juan Capistrano.
caption: Map of the Oso Creek subwatershed within the San Juan Creek basin
exif: {"Image Orientation": "Horizontal (normal)", "Image XResolution": "72", "Image YResolution": "72", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Adobe Photoshop Elements 4.0.1 Macintosh", "Image DateTime": "2009:08:17 13:02:45", "Image ExifOffset": "176", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "314", "Thumbnail JPEGInterchangeFormatLength": "10015", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "1000", "EXIF ExifImageLength": "1000"}