The Outlet Creek Basin is one of the headwaters of the Eel River, the third largest river system in California. The Basin drains an area of 160 square miles of Northern California’s Coast Range with its headwaters inland about 27 miles at an elevation of 2,400 feet. It is located in north central Mendocino County, approximately 148 miles north of San Francisco and eight miles north of Willits. Outlet Creek is about 118 miles long and receives water from over 12 tributary streams. There are approximately 150 perennial stream miles in the Basin.
The Basin has a Mediterranean climate characterized by cool, wet winters with high runoff and dry, warm summers with reduced or absent flows in some streams. The air temperatures range from 14F to104F. It is fairly common to receive up to 3 inches of snow each year. The west side is commonly influenced by summer coastal fog which can insulate streams from the higher air temperatures experienced by other geographically oriented streams.
Regional uplifting and faulting of the Franciscan geology in the Eel River watershed have produced physical characteristics such as steep slopes and exposed sedimentary cliffs that make the entire basin especially prone to erosion. The combination of steep topography and unstable geology combined with high precipitation and high peak flows have contributed to naturally high levels of fine sediment in the Outlet Creek Basin. The Outlet Basin is composed of Franciscan, Alluvium, and Coastal Belt geologic terranes. Most headwaters creeks in the basin are composed of Franciscan geology. All of the lower reaches of the creeks running through Little Lake Valley are composed of Alluvium.
The Outlet Creek Basin was occupied by Pomo Native Americans when the first European settlers arrived in the early 1840s. Old growth redwood forest dominated the northwestern portion of the basin while Douglas fir and ponderosa pine dominated the north facing eastern portion. Oak-woodlands and grasslands predominate on higher, inland terrain that is out of the foggy coastal marine influence.
The only post office town is Willits. In 2000, the average population density was ~25 persons per square mile in Mendocino County and the census recorded 5,073 people in Willits with an additional 7,000 living in the surrounding areas. The basin is 95% privately owned. Compared to other north coast watersheds, the basin has one of the longest records of timber harvest and ranching activities, which began in the mid-1800s and continue today.
Historically and currently, Chinook and coho salmon and winter-run steelhead trout inhabit the Outlet Creek Basin. There are 16 known fish species; four are native and anadromous, and fourteen are freshwater with six species being native and eight species being non-native species. The basin appears to have relatively small populations of Chinook and coho salmon, and steelhead trout populations.