Ten Mile River (California)

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 10 miles (16 km) north of the mouth of the Noyo River.[2][3] The lands around lower Ten Mile River provide valuable freshwater and saltwater marsh habitat for a variety of birds.[4] 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 five nautical miles.[5] Ten Mile Beach is also part of MacKerricher State Park, which extends approximately five miles southward from the mouth of the river to Cleone and includes approximately 1,300 acres (530 ha) of the "most pristine stretch of sand dunes [in California]."[6]

Ten Mile River (California)
Ten Mile Creek, Tenmile[1]
Ten Mile River, looking north from California 1
Location
CountryUnited States
StateCalifornia
RegionMendocino
Physical characteristics
SourceConfluence of North Fork Ten Mile Creek and Middle Fork Ten Mile Creek
 • coordinates39°33′10″N 123°46′01″W[1]
 • elevation49 ft (15 m)
MouthPacific Ocean
 • coordinates
39°33′10″N 123°46′01″W[1]
 • elevation
0 ft (0 m)[1]
Basin features
Tributaries 
 • leftMiddle Fork Ten Mile Creek, Mill Creek, California, South Fork Ten Mile Creek
 • rightNorth Fork Ten Mile Creek

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, ten miles 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.[7] 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.[4][8] Timber in the area is logged on a 60-year rotation.[7]

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".[9] 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.[10][11] After studies found that the 1954 bridge was insufficiently earthquake-safe,[12] a new concrete box girder bridge on Highway 1 was constructed in 2009.[13][14][15][16] The new bridge is 45 feet (14 m) wide and 1,479 feet (451 m) long; it cost $43.5 million to construct.[10]

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 five nautical miles.[5] 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.[17] 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 saltmarshes 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.[17] 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).[18] 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.

Historically, the Ten Mile River had an important Coho Salmon population, but it has since been surpassed by Steelhead.[19] The river provides cold freshwater habitat for fish migration and spawning,[20] but is environmentally impacted by logging like many rivers in the area. A United States Environmental Protection Agency study reported that "Sediment was determined to be impacting the cold water fishery, a beneficial use of the Ten Mile River watershed, including the migration, spawning, reproduction, and early development of cold water fish such as coho salmon and steelhead trout. Cold freshwater and estuarine habitats are also designated beneficial uses of the Ten Mile River watershed."[21] The spawning population of coho salmon in Ten Mile River has been observed to decrease from an estimate of 6000 fish in the early 1960s to much lower numbers ranging from 14 to 250 in the 1990s. Contributing factors to this decline include natural variability, excessive sedimentation from logging, increased water temperatures due to the removal of riparian vegetation, and reduced woody debris in salmon habitats.[22] As a result of these impacts, the river was listed as sediment impaired under section 303(d) of the Clean water Act in 1998.[19] Improved timber harvest practices and regular road maintenance have reduced sedimentation and allowed continued active management for timber harvest in 45% of the Ten Mile River watershed.[23]

Watershed

The Ten Mile River mainstem begins at the confluence of North Fork Ten Mile River and Middle Fork Ten Mile River, flows southwest then northwest to the Pacific Ocean 5.7 miles (9.2 km) south of Westport. The North Fork Ten Mile River begins at elevation 2,400 feet (730 m).[24] The Middle Fork Ten Mile River begins at elevation 2,460 feet (750 m) on the north side of Sherwood Peak.[25] The middle and north forks of the river are each 15 miles (24 km) long, and the river extends for seven more miles from their confluence to its mouth at the Pacific Ocean.[2] The watershed drains approximately 120 square miles (310 km2) and is neighbored to the south by the Noyo River watershed and to the east and north by the South Fork Eel River watershed.[2]

River flow is precipitation-driven. Annual rainfall averages 40 inches on the coast and 51 inches inland. Under low flow conditions, sand bars constrict the narrow river mouth, often blocking it entirely in summer. When this occurs, the estuarine portion of the Ten Mile River temporarily becomes a freshwater lagoon, where salinity and tidal influence are both reduced. Estuarine conditions return when large storm events re-establish ocean connectivity.[17]

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See also

References
  1. "Ten Mile River". Geographic Names Information System. United States Geological Survey.
  2. Durham, David L. (1998), California's geographic names: a gazetteer of historic and modern names of the state, Quill Driver Books, p. 155, ISBN 978-1-884995-14-9.
  3. Palmer, Lyman L. (1967), History of Mendocino County, California, comprising its geography, geology, topography, climatography, springs and timber, Mendocino County Historical Society, p. 423.
  4. Franks, Jonathan (1996), Exploring the North Coast, Raincoast Books, p. 149, ISBN 0-8118-0910-2.
  5. California Department of Fish and Wildlife (2013). Guide to the Northern California Marine Protected Areas: California-Oregon Border to Point Arena (Report).
  6. Hall, Carl T. (June 16, 2005), "A little something for fans of sand: California home to some of most impressive dunes", San Francisco Chronicle.
  7. Timber Harvest in KRIS Ten Mile, Klamath Resource Information System, retrieved 2010-08-21.
  8. Sediment Information in KRIS Ten Mile River, Klamath Resource Information System, retrieved 2010-08-25.
  9. Browne, J. Ross (August 1861), "Coast Rangers Of California", Harper's New Monthly Magazine, 23 (135): 306–316.
  10. Ten Mile River Bridge, California Department of Transportation, retrieved 2010-08-21.
  11. Old Ten Mile River Bridge, Historic Brides of the United States, retrieved 2010-08-21.
  12. Hymon, Steve (August 5, 2008), "Road Sage: Many bridges are too shaky for extreme quakes", Los Angeles Times.
  13. Hartzell, Frank (November 23, 2005), "New Ten Mile Bridge design challenged", Mendocino Beacon.
  14. "Coastal Commission to hold Ten Mile Bridge hearing in Santa Rosa", Mendocino Beacon, June 8, 2006.
  15. "Ten Mile River Bridge almost completed", Fort Bragg Advocate-News, April 2, 2009.
  16. Reed, Tony (May 14, 2009), "Ten Mile River bridged", Mendocino Beacon.
  17. Osborn, Katherine (December 2017). Seasonal fish and invertebrate communities in three northern California estuaries (M.S. thesis). Humboldt State University.
  18. Recovery Plan for the Tidewater Goby (Eucyclogobius newberryi) (PDF) (Report). Portland, Oregon: U.S. Fish and Wildlife Service. 2005. p. 199. Retrieved 2010-12-03.
  19. North Coast Regional Water Quality Control Board (2005). Watershed Planning Chapter, Section 2.3.4. Ten Mile River Watershed (PDF) (Report). Santa Rosa, CA.
  20. State of California Water Quality Control Plan North Coastal Basin 1B July 1975 p.13
  21. Sediment Information in KRIS Ten Mile River, Klamath Resource Information System, retrieved 2010-08-21.
  22. Working Hypotheses Concerning Salmon and Steelhead Limiting Factors, Klamath Resource Information System, retrieved 2010-08-21.
  23. Graham Matthews and Associates (2000). Sediment Source Analysis and Preliminary Sediment Budget for the Ten Mile River, Mendocino County, California (PDF) (Report). Prepared for Tetra Tech Inc.
  24. "North Fork Ten Mile River". Geographic Names Information System. United States Geological Survey.
  25. "Middle Fork Ten Mile River". Geographic Names Information System. United States Geological Survey.
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