Laguna Canyon - Geography and Geology

Geography and Geology

Laguna Canyon is a generally north-south running gorge approximately 8 miles (13 km) long and 1 mile (1.6 km) wide at the broadest points. The city of Irvine lies to the north, Lake Forest and Aliso Viejo to the east, the undeveloped San Joaquin Hills to the west, and Laguna Beach to the south. The drainage divide of the canyon is located near its northern end, separating Laguna Canyon from the San Diego Creek watershed.

California State Route 133, alternatively called the Laguna Canyon Road, winds through Laguna Canyon for the entire length of the gorge. California State Route 73 bisects the gorge east-west. The lower section of the canyon is contained in the Laguna Coast Wilderness, while the upper section is contained in a few smaller wilderness preserves. Some of the lower section has development, but the upper section remains relatively undeveloped. The northernmost extreme of the canyon lies near a residential area that adjoins Interstate 405.

The canyon was most likely formed by San Diego Creek cutting through the rising San Joaquin Hills over a span of about 1.22 million years. At some point, however, the creek changed course, and the water gap it had formed was walled off by the mountains and became a separate watershed. The gradient of the drainage divide separating Laguna Canyon and the San Diego Creek watershed is, however, very small.