San Geronimo Creek is a stream in
Marin County, California
Marin County is a County (United States), county located in the northwestern part of the San Francisco Bay Area of the U.S. state of California. As of the 2020 United States Census, 2020 census, the population was 262,231. Its county seat and ...
,
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
, which feeds into
Lagunitas Creek
Lagunitas Creek is a -longU.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map, accessed December 27, 2017 northward-flowing stream in Marin County, California. It is critically important to the large ...
below
Kent Lake
Kent Lake is a reservoir in western Marin County, California formed by the construction of Peters Dam across Lagunitas Creek. Built in 1954, the lake is the most recent lake of the Marin Municipal Water District, as well as the largest. It lie ...
.
Course
The creek rises in the hills west of the town of
Fairfax. It descends northward to
Woodacre, where it turns westward and parallels
Sir Francis Drake Boulevard
Sir Francis Drake Boulevard is an approximately 43.8 mile east–west arterial road in Marin County, California, running from the trailhead for Point Reyes Lighthouse at the end of the Point Reyes Peninsula to Interstate 580 just west of t ...
through the villages of
San Geronimo,
Forest Knolls, and Lagunitas. It then turns southwestward and joins Lagunitas Creek at the eastern edge of the
Samuel P. Taylor State Park.
Ecology
The 6000 acre San Geronimo Creek watershed is within the 60,000 acre Lagunitas Creek Watershed, which is home to the largest-remaining wild run of
coho salmon
The coho salmon (''Oncorhynchus kisutch;'' Karuk: achvuun) is a species of anadromous fish in the salmon family (biology), family and one of the five Pacific salmon species. Coho salmon are also known as silver salmon or "silvers". The scientif ...
in central California. These coho are part of the "Central California Coast Evolutionarily Significant Unit," or CCC ESU, and are listed as "endangered" at both the state and federal level.
Efforts are also being made to protect and restore streams and habitat in the
San Geronimo Valley
San Geronimo Valley is located in Marin County, California, composed of four unincorporated towns: Woodacre, San Geronimo, Forest Knolls, and Lagunitas. It is a fairly close-knit community, with a rather liberal citizenry. The farther west ...
, where upwards of 20% of the Lagunitas salmon spawn each year and where as much as 1/5 of the juvenile salmon (or fry) spend their entire freshwater lives.
Spawning salmon and trout may be viewed at Roy's Pools, located about west of
Fairfax. There are jump pools and a fish ladder.
Bridges
At least seven bridges span San Geronimo Creek:
* at Meadow Way, south of Sir Francis Drake Boulevard, a concrete continuous slab long, built in 1965.
* at Lagunitas Road, south of Sir Francis Drake Boulevard, a
prestressed concrete
Prestressed concrete is a form of concrete used in construction. It is substantially "prestressed" ( compressed) during production, in a manner that strengthens it against tensile forces which will exist when in service. Post-tensioned concreted i ...
tee beam
A T-beam (or tee beam), used in construction, is a load-bearing structure of reinforced concrete, wood or metal, with a -shaped cross section. The top of the -shaped cross section serves as a flange or compression member in resisting compress ...
long, built in 1964.
* Mountain View Road at Sir Francis Drake Boulevard, a steel bridge long, built in 1962 and reconstructed in 1974.
* at Montezuma Road south of Sir Francis Drake Boulevard, a concrete culvert long, built in 1938.
* at Sir Francis Drake Boulevard east of
State Route 1, a concrete tee beam long, built in 1929 and reconstructed in 1993.
* at Creamery Road, south of Sir Francis Drake Boulevard, a concrete Tee Beam long, built in 1948.
* at San Geronimo Valley Drive, east of Nicasio Valley Road, a concrete tee beam long, built in 1929.
See also
*
List of watercourses in the San Francisco Bay Area
These watercourses (rivers, creeks, sloughs, etc.) in the San Francisco Bay Area are grouped according to the bodies of water they flow into. Tributaries are listed under the watercourses they feed, sorted by the elevation of the confluence so tha ...
References
{{Reflist
Rivers of Marin County, California
Rivers of Northern California
West Marin