Malibu Creek is the the largest creek in the Santa Monica Mountains of southern California. With a watershed of over 100 square miles, it is about ten times larger than the second largest creek, Topanga Creek, and sustains a good flow even during the dry season. Interestingly, this creek actually passes right through the mountain range, in a deep gorge between the second and third highest mountains in the range. Most of its waters come from the relatively moist northern slopes of the mountains, and from the nearby Simi Hills. In and near Malibu Creek State Park, several creeks, such as Triunfo Creek, Medea Creek, Las Virgines Creek, and Cold Creek join to form Malibu Creek. After this point it plunges through a deep gorge into the ocean.

In addition to being the largest drainage in the area, this creek is also by far the most human-impacted. A large percentage of the creek's upper drainage is urbanized, consisting of most of the cities of Thousand Oaks and Agoura Hills, among others. In such a steep, rocky environment as the Santa Monica Mountains, floods have always occurred. However, with many square miles of concrete upstream, the floods have become far more frequent and severe than in the past. Even storms too small to put more than a trickle of water in nearby creeks can cause raging walls of muddy water to tear through Malibu Canyon into the sea, complete with pollutants and debris.

In addition, a small 'flood control' dam exists in the canyon. Even when new, this dam was far too small to hold back this creek, which according to some unverified sources, can contain almost as much water as the Mississippi River during its more severe floods. However, what was once a lake has been filled with mud and debris by many mudslides and is long gone. The dam still stands, and keeps native steelhead trout from swimming up the creek. Removal of this dam would be very difficult due to the amount of debris behind it.

Despite the problems associated with this creek, it is still a scenic and important part of the mountains. The creek supports a healthy grove of alders, oaks, willows, and sycamores, and is very important to wildlife during the dry summer months. It is also a scenic addition to the Malibu Creek State Park, although i can't recommend swimming in the water or eating fish caught here.