Portal:Greater Los Angeles/Selected article/22

Aliso Creek (Spanish for "Alder Creek"; also called Alisos Creek) is a 19-mile (31 km)-long urban stream that runs through Orange County in the U.S. state of California from the Santa Ana Mountains to the Pacific Ocean, collecting seven main tributaries. The creek is mostly channelized, and as of 2004, the 30.4-square-mile (78.7 km²) watershed had a population of 149,087 divided among seven incorporated cities.

The creek flows generally south-southwest through a narrow coastal watershed at the southern extreme of the arid Los Angeles Basin in a fairly straight course. Owing to the submersion of Southern California in the Pacific Ocean as recently as 10 million years ago, the creek flows over marine sedimentary rock that dates from the late Eocene to the Pliocene. The present-day form of the watershed, with its broad sediment-filled valleys and deeply eroded side canyons, was shaped by a climate change during the previous Ice Age that produced Aliso Canyon, the creek's final gorge. more...