Ten Mile River (also known as Ten Mile Creek) is in northern Mendocino County, California, United States. It is named for the fact that its mouth is north of the mouth of the Noyo River. The lands around lower Ten Mile River provide valuable freshwater and saltwater marsh habitat for a variety of birds. The Ten Mile River Estuary, Ten Mile Beach, and Ten Mile State Marine Reserve together form a marine protected area that extends from the estuary out to . Ten Mile Beach is also part of MacKerricher State Park, which extends approximately southward from the mouth of the river to Cleone and includes approximately of the "most pristine stretch of sand dunes [in California]."
History
The Ten Mile River basin has been logged continuously since the early 1870s. At first, trees were cut using single-bladed axes and dragged by oxen to mills at Fort Bragg, to the south. Railroad lines were introduced on the South Fork in 1910 and on the other parts of the river in the 1920s. In the 1930s, the railroads were replaced by tractor roads; after the passage of the California Forest Practice Act in 1973, tractor logging on steeper slopes was supplanted by more environmentally friendly practices such as the use of cables. The timber on both sides of the river was logged by the Georgia Pacific Company until 1999, when Georgia-Pacific's holdings in the area were acquired by the Hawthorne Timber Company. Timber in the area is logged on a 60-year rotation.
An 1861 story in Harper's Monthly includes a passage recounting the crossing of Ten Mile River: "We found the crossing a little dangerous on account of the tide, which sometimes renders it impassable for several hours, except by swimming. With some plunging, spurring, and kicking, the opposite side was gained in due time". Later, the river was spanned near its mouth by a bridge on California State Route 1, north of the community of Inglenook. A concrete beam bridge replaced an older wooden deck truss bridge in 1954. After studies found that the 1954 bridge was insufficiently earthquake-safe, a new concrete box girder bridge on Highway 1 was constructed in 2009. The new bridge is wide and long; it cost $43.5 million to construct.
In 2012, the Ten Mile River Estuary was designated as a State Marine Conservation Area (SMCA) under the Marine Life Protection Act. At the same time, Ten Mile Beach SMCA and Ten Mile State State Marine Reserve were established, creating a continuous Marine Protected Area (MPA) zone that extends from the upper limit of the estuary out to . The MPA zone complements the protections for neighboring lands, including MacKerricher State Park and Inglenook Fen-Ten Mile Dunes Natural Preserve.
Ecology
The Ten Mile River has intermittent ocean connectivity, so that the estuary effectively becomes a freshwater lagoon in some years. As a result, seasonal use by anadromous and marine fishes varies significantly from year to year. When the mouth is open, Ten Mile River Estuary serves as a migration corridor for anadromous salmonids and a rearing area for juvenile coastal fishes, including flatfish and surfperch. In summer, juvenile shiner surfperch (Cymatogaster aggregata) will flock to the highly productive salt marshes when tidally flooded. This changes in years when the mouth is closed - salinities are reduced, slack tides can persist for hours, and the winter fish community of sculpins and Three-spined Stickleback (Gasterosteus aculeatus) continues to dominate through summer. Lagoon conditions are ideal for the endangered Tidewater goby (Eucyclogobius newberryi), which prefers slow-moving habitats. The goby is found in the estuary and several miles upstream in areas impounded by California Golden beavers (Castor canadensis subauratus). The dunes surrounding the estuary are home to rare plant species, while the freshwater and saltwater marshes along the estuary provide critical bird habitat. The area is popular for paddle sports and birding.