Course of San Juan Creek

San Juan Creek begins in the southern Santa Ana Mountains, a few miles northwest of Lake Elsinore.

[1] Paralleling the Ortega Highway (California State Route 74) the creek flows erratically south, west and occasionally northwest.

The creek channel in the uppermost few miles is a narrow mountain stream with many rapids and waterfalls, which include a series of large 5-to-15-foot (1.5 to 4.6 m) cascades, known as San Juan Falls.

Just below the falls, a small perennial watercourse trickles into San Juan Creek on the left bank.

[4] About 1 mi (1.6 km) below the falls, deposits begin to become apparent on the floor of the widening valley, and the creek spreads out, with short reaches of cascades between slackwater pools and more gradual courses.

[5] The creek bed meanders in large arcs, separated by numerous islands and bands of vegetation.

The man-made structure is a small gabion located at the entrance of Caspers Wilderness Park, which is near the west boundary of the Cleveland National Forest.

After passing beneath the interstate, it is abruptly diverted into a trapezoidal flood control channel, with concrete levees and an earthen riverbed.

The creek crosses the boundary between San Juan Capistrano and the city of Dana Point, where its channel widens and further shallows.

[1] Directly after this final crossing, San Juan Creek flows into a fresh-water lagoon 900 feet (270 m) south of the north end of Doheny State Beach, created by a tongue of sand that blocks the water from reaching the ocean.

[6] Occasionally, the sand berm impounding the water is breached, causing massive runoff into the ocean.