The Santa Ana River is the largest river entirely within Southern California in the United States. It rises in the San Bernardino Mountains and flows for most of its length through San Bernardino and Riverside counties, before cutting through the northern Santa Ana Mountains via Santa Ana Canyon and flowing southwest through urban Orange County to drain into the Pacific Ocean. The Santa Ana River is 96 miles (154 km) long, and its drainage basin is 2,650 square miles (6,900 km2) in size.
The Santa Ana Mountains are a short peninsular mountain range along the coast of Southern California in the United States. They extend for approximately 61 miles (98 km) southeast of the Los Angeles Basin largely along the border between Orange and Riverside counties.
Trabuco Canyon is a small unincorporated community located in the foothills of the Santa Ana Mountains in eastern Orange County, California, and lies partly within the Cleveland National Forest.
The San Joaquin Hills are a low mountain range of the Peninsular Ranges System, located in coastal Orange County, California.
San Juan Creek, also called the San Juan River, is a 29-mile (47 km) long stream in Orange and Riverside Counties, draining a watershed of 133.9 square miles (347 km2). Its mainstem begins in the southern Santa Ana Mountains in the Cleveland National Forest. It winds west and south through San Juan Canyon, and is joined by Arroyo Trabuco as it passes through San Juan Capistrano. It flows into the Pacific Ocean at Doheny State Beach. San Juan Canyon provides a major part of the route for California State Route 74.
Aliso Creek is a 19.8-mile (31.9 km)-long, mostly urban stream in south Orange County, California. Originating in the Cleveland National Forest in the Santa Ana Mountains, it flows generally southwest and empties into the Pacific Ocean at Laguna Beach. The creek's watershed drains 34.9 square miles (90 km2), and it is joined by seven main tributaries. As of 2018, the watershed had a population of 144,000 divided among seven incorporated cities.
Oso Creek is an approximately 13.5-mile (21.7 km) tributary of Arroyo Trabuco in southern Orange County in the U.S. state of California. Draining about 20 square miles (52 km2) 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.
Arroyo Trabuco is a 22-mile (35 km)-long stream in coastal southern California in the United States. Rising in a rugged canyon in the Santa Ana Mountains of Orange County, the creek flows west and southwest before emptying into San Juan Creek in the city of San Juan Capistrano. Arroyo Trabuco's watershed drains 54 square miles (140 km2) of hilly, semi-arid land and lies mostly in Orange County, with a small portion extending northward into Riverside County. The lower section of the creek flows through three incorporated cities and is moderately polluted by urban and agricultural runoff.
Salt Creek is a small coastal stream in southern Orange County in the U.S. state of California. The 4-mile (6.4 km) creek drains 6.1 square miles (16 km2) in parts of the cities of Laguna Niguel, Dana Point, and San Juan Capistrano. The mostly channelized creek has no named surface tributaries. The creek begins in the central portion of the city of Laguna Niguel and flows west and south through a narrow canyon referred to as the Salt Creek Corridor, which is mostly inside a long and narrow regional park. It then flows into the Monarch Beach Golf Course in the city of Dana Point and enters a subsurface storm channel which carries it to its discharge point at Salt Creek County Beach.
Santiago Creek is a major watercourse in Orange County in the U.S. state of California. About 34 miles (55 km) long, it drains most of the northern Santa Ana Mountains and is a tributary to the Santa Ana River. It is one of the longest watercourses entirely within the county. The creek shares its name with Santiago Peak, at 5,687 ft (1,733 m) the highest point in Orange County, on whose slopes its headwaters rise.
Laguna Canyon, also called Cañada de las Lagunas, is a gorge that cuts through the San Joaquin Hills in southern Orange County, California, in the United States, directly south of the city of Irvine. The canyon runs from northeast to southwest, and is drained on the north side by tributaries of San Diego Creek and on the south by Laguna Canyon Creek. It is deeper and more rugged on the southwestern end near Laguna Beach.
San Diego Creek is a 16-mile (26 km) urban waterway flowing into Upper Newport Bay in Orange County, California in the United States. Its watershed covers 112.2 square miles (291 km2) in parts of eight cities, including Irvine, Tustin, and Costa Mesa. From its headwaters in Laguna Woods the creek flows northwest to its confluence with Peters Canyon Wash, where it turns abruptly southwest towards the bay. Most of the creek has been converted to a concrete flood control channel, but it also provides important aquatic and riparian habitat along its course and its tidal estuary.
Sulphur Creek is a 4.5-mile (7.2 km) tributary of Aliso Creek in Orange County in the U.S. state of California. The creek drains about 6 square miles (16 km2) of residential communities and parks in the southern San Joaquin Hills.
Coyote Creek is a principal tributary of the San Gabriel River in northwest Orange County, southeast Los Angeles County, and southwest Riverside County, California. It drains a land area of roughly 41.3 square miles (107 km2) covering eight major cities, including Brea, Buena Park, Fullerton, Hawaiian Gardens, La Habra, Lakewood, La Palma, and Long Beach. Some major tributaries of the creek in the highly urbanized watershed include Brea Creek, Fullerton Creek, and Carbon Creek. The mostly flat creek basin is separated by a series of low mountains, and is bounded by several small mountain ranges, including the Chino Hills, Puente Hills, and West Coyote Hills.
Brea Creek is one of four principal tributaries of Coyote Creek, which is a lower tributary of the San Gabriel River in California. It drains parts of Orange, Riverside, and San Bernardino counties. The creek flows 11.7 miles (18.8 km) from the cities of Brea and Anaheim to Whittier, where its mouth is on the left bank of Coyote Creek, at a point 481 feet (147 m) lower in elevation.
Bell Canyon is a major drainage of the Santa Ana Mountains in Orange County, California in the United States. Bell Creek flows about 14.4 miles (23.2 km) in a southerly direction to its confluence with San Juan Creek. The Bell Canyon drainage is located to the east and parallel to Cañada Gobernadora, and to the south of Trabuco Creek. After Trabuco Creek, it is the second largest tributary of San Juan Creek in terms of length and its watershed area of 26 square miles (67 km2).
San Juan Creek is a creek in Orange County in the U.S. state of California. It is about 29 miles (47 km) long, and along with its major tributary, Trabuco Creek, drains 133 square miles (340 km2) near the southernmost extent of Orange County. This article describes the course of San Juan Creek.
San Mateo Creek is a stream in Southern California in the United States, whose watershed mostly straddles the border of Orange and San Diego Counties. It is about 22 miles (35 km) long, flowing in a generally southwesterly direction. Draining a broad valley bounded by the Santa Ana Mountains and Santa Margarita Mountains, San Mateo Creek is notable for being one of the last unchannelized streams in Southern California.
