Decades-old O’Neill Regional Park near Rancho Santa Margarita has a newer “appendage” — a six-mile piece of the Arroyo Trabuco, a shallow, gradually descending canyon going south toward Mission Viejo. An old fire road along the arroyo stream has been converted into a hike-and-bike trail, making possible an easygoing trip through the canyon. Those on foot may want to arrange a drop-off-and-pick-up scheme and avoid retracing steps by going one-way downhill (north to south). Mountain bikers, though, should have no problem completing the 12-mile round-trip.
Begin at the west end of the Oak Grove day-use area, west of the O’Neill Park office, where the well-marked trail down along the Arroyo Trabuco begins. As summer approaches, not much water can be found in the arroyo bottom. You soon pass under a massive twin bridge (Foothill Transportation Corridor toll road, Highway 241) and later pass under another equally huge bridge (Santa Margarita Parkway). As an environmental mitigation for the construction of these bridges, county workers and volunteers planted on the arroyo banks thousands of native trees and shrubs — live oak, sycamore, toyon, mulefat, and willow.
At 1.9 miles, well past the second bridge, the trail swings left across the creek and ascends moderately toward the rim of the shallow gorge and toward a subdivision built upon the sloping plain to the east, called Plano Trabuco. The plano (“plain” in English) is a broad terrace made up of alluvial deposits cast off of the Santa Ana Mountains. Over recent geologic time, the abrasive floodwaters of Arroyo Trabuco have cut about 100 feet deep into Plano Trabuco’s soft sediments. Plano Trabuco acquired its name in 1769, when a Spanish soldier traveling with the Portola expedition lost a blunderbuss (trabuco) there. A string of contemporary place names are descended from the original: Arroyo Trabuco, Trabuco Canyon, and the Trabuco Ranger District — the part of Cleveland National Forest that encompasses the Santa Ana Mountains.
After a moderate ascent, the Arroyo Trabuco Trail sidles up to a residential street called Arroyo Vista, where there is a signed access point for the trail. Plenty of curbside parking is available here, if you want to plan a shorter trip up or down the arroyo. A mile farther, the trail descends back into the gorge. On the left, before you begin the descent, notice a small structure accompanied by a historical plaque. This marks the campsite, designated San Francisco Solano, used by the Portola expedition on the night of July 24, 1769.
After the descent, the trail continues for another two miles down alongside the wide floodplain, always staying close to the streambed. This is perhaps the most agreeable part of the arroyo with gnarled sycamores and oaks alternating with grassy clearings. After three stream crossings, the Oso Parkway bridge looms high overhead. Underneath it you can pick up a powerline access road up the right (west) slope of the arroyo and ascend to reach the shoulder of Oso Parkway. No parking is provided at this end of the trail, though a concrete apron allows westbound cars to pull off the parkway at that spot and pick up passengers.
This article contains information about a publicly owned recreation or wilderness area. Trails and pathways are not necessarily marked. Conditions can change rapidly. Hikers should be properly equipped and have safety and navigational skills. The Reader and Jerry Schad assume no responsibility for any adverse experience.
Hike or bike down the Arroyo Trabuco floodplain, following one of Orange County’s beautiful linear parks.
Distance from downtown San Diego: 80 miles
Hiking/biking length: 6 miles one-way
Difficulty: Moderate (one way)