Southern Coastal Creeks Watershed
Marin’s Southern Coastal watersheds include Webb Creek, Lone Tree Creek, Cold Stream, Redwood Creek, Alder Creek, Rodeo Lagoon, and Tennessee Valley.
Webb Creek originates at the peaks of Mt. Tamalpais and flows towards the Pacific Ocean through Steep Ravine Canyon and Mt. Tamalpais State Park. The creek drains into the Pacific between Stinson Beach and Rocky Point. North of the community of Muir Beach, Lone Tree Creek and Cold Stream drain the area west of the ridge line that forms the Dipsea and Coastal Fire Roads. They flow through the lands of the Golden Gate National Recreation Area (GGNRA) and into the Pacific Ocean.
The Redwood Creek watershed begins at the peak of Mt. Tamalpais and extends southwest to Muir Beach where it drains into the Pacific Ocean. The watershed encompasses an area of less than 9 square miles. At the mouth of the watershed is Big Lagoon, an intermittent tidal lagoon. The watershed provides habitat for several sensitive species, including northern spotted owl, California red-legged frog, Coho salmon, and steelhead trout. The watershed is located in a recognized global biodiversity “hot spot” (one of only 5 in the continental United States) and is also within Golden Gate Biosphere Reserve. The main tributaries to Redwood Creek include Bootjack, Fern, Kent Canyon, Rattlesnake, and Spike Buck Creeks.
Alder Creek drains the western half of the Bolinas Mesa, including most of the town of Bolinas itself. The creek flows into Duxbury Reef and the Pacific Ocean through Agate Beach; it is typically dry from April to November. To the north, Arroyo Hondo and several smaller tributaries also flow into Duxbury Reef; these are part of Point Reyes National Seashore. The shoreline throughout the watershed is part of the Duxbury Reef Area of Special Biological Significance (ASBS).
The most southerly coastal streams are the Rodeo Lagoon and Tennessee Valley drainages, located north of Point Bonita and south of the Muir Beach community and Coyote Ridge. These systems flow through the lands of GGNRA and along the western slopes of the Marin Peninsula. Approximately five intermittent streams flow through the 2 square miles of the Tennessee Valley drainage. Two main drainages flow from the north and south into Rodeo Lagoon near Fort Cronkhite; the Lagoon drains an area of approximately 4 square miles.
The lower watersheds of Webb Creek, Lone Tree Creek, and Cold Stream are primarily coastal scrub; the upper watersheds contain Douglas fir and redwood forest. Oak-bay woodland and redwood forest occur along the drainages, with patches of grassland habitat.
The Redwood Creek watershed contains a variety of habitat types including coastal chaparral, grassland, old-growth redwood forest, mixed hardwood forest, seasonal wetlands, and riparian woodlands. Prior to the land use changes that followed European colonization of the watershed, a large intermittently tidal lagoon occurred at the mouth of Redwood Creek. This lagoon once covered an area of approximately 25 acres; only a remnant of the lagoon remains today.
The Alder watershed is predominantly composed of residential and rural residential development. Undeveloped areas are primarily annual grassland and coastal scrub, with small groves of eucalyptus and Monterey pine. Duxbury Reef, considered the largest shale reef in North America, provides an extensive system of rocky intertidal and subtidal habitat that supports large areas of kelp beds and many marine invertebrates and fish, and is an important haul-out site for harbor seals. Steep, unstable cliffs separate the reef and a narrow strip of sandy beach from the Bolinas Mesa.
The Tennessee Valley watershed is largely composed of grassland and coastal scrub habitats with a small freshwater marsh near the lower watershed. Similar habitat types occur within the Rodeo Lagoon watershed. Rodeo Lagoon is an important aquatic resource for a variety of native fish and wildlife species.
Fish and Wildlife
Northern spotted owls have been recorded along Webb Creek, and Tamalpais oaks occur at the top of Webb Creek and Lone Tree Creek watersheds. There are no historical or current records of special-status fish species in these watersheds.
In Redwood Creek, identified special-status species include Coho salmon, steelhead trout, California red-legged frog, monarch butterflies, northwestern pond turtle, and northern spotted owl have been observed in the watershed. Special-status plants include Mt. Tamalpais manzanita, Tamalpais oak, Tiburon buckwheat, and Mount Tamalpais jewel-flower.
Redwood Creek was previously considered the southernmost stable population of Coho salmon. However, in winter of 2007-2008, no returning adults were recorded, for the first time since the 1940s; nor were any redds observed (Ketcham 2008 1). An 80% decline in spawning salmon was observed in most western Marin County creeks that year. One cause of the decline may have been the lack of local coastal upwelling in 2006, which normally brings nutrient-rich waters to Coho salmon smolts in late spring and early summer. One Coho salmon redd with adult Coho salmon was observed in Green Gulch Creek in the winter of 2006-07 (personal communication L. Prunuske with Jeremy Levie 2008).
Monarch butterflies have been observed roosting in eucalyptus trees in the Alder Creek watershed. Harbor seals haul out at Duxbury Reef. In addition, six species of algae and marine vascular plants, and 89 species of invertebrates, have been identified at Duxbury Reef (SWRCB 2008 2). No fish have been observed in the seasonal drainages of the Bolinas Mesa.
Special-status species in the Tennessee Valley drainage include Salt marsh common yellowthroat and monarch butterfly. California brown pelican, salt marsh common yellowthroat, monarch butterfly, Mission blue butterfly, Point Reyes jumping mouse, tidewater goby, and Franciscan thistle have been recorded in Rodeo Lagoon.
Human Habitation, Land Use, and Resource Conservation
Land Use Imperviousness
Webb Creek, Lone Tree Creek, and Cold Stream watersheds occur within state and federal lands, including Mt. Tamalpais State Park and Golden Gate National Recreation Area. In the Webb Creek watershed, there is a small military complex and a campground perched on the rocky bluffs along the ocean.
95% of the land within the Redwood Creek watershed is in public ownership. Within the watershed boundaries lie Mt. Tamalpais State Park, National Park Service lands, including Muir Woods National Monument and portions of Golden Gate National Recreation Area, and Marin Municipal Water District lands. Three private communities occupy a small portion of the watershed: Green Gulch Farm, Muir Woods Park, and the Muir Beach community.
The Alder Creek watershed is primarily composed of urban and rural residential areas in and around the town of Bolinas. Wastewater is handled in part by the Bolinas Community Public Utility District’s sanitary sewer system and treatment ponds, and in part by on-site septic systems. Many residents have small numbers of livestock on their property. A few commercial gardens and other small businesses, and portions of livestock ranches, also occur in the Alder Creek watershed. Agate Beach is a popular tidepooling spot open to the public; facilities include a parking lot and portable restrooms. A water service moratorium set by the Bolinas Community Public Utilities District and Marin County land use restrictions limit the likelihood of future development in the watershed. Aside from a concrete culvert where a seasonal tributary joins Alder Creek near Agate Beach, there are no stormwater management facilities for Bolinas. Most surface runoff flows to ditches and channels paralleling roadways and into Alder Creek.
Marin County Stormwater Pollution Prevention Program (MCSTOPPP) has applied for funding to reduce nonpoint source pollution into Duxbury Reef and Point Reyes Headlands. As part of the Tomales Bay Integrated Coastal Watershed Management Plan, a watershed assessment for Duxbury Reef and other local Areas of Special Biological Significance was completed.
In 2003, a Redwood Creek Watershed Vision for the Future was developed through a collaborative effort between public and private landowners and resource managers to successfully manage the Redwood Creek watershed. The public agencies involved in the vision included California Department of Fish and Game, Marin Municipal Water District, County of Marin, Muir Beach Community Services District, and the National Park Service. Golden Gate National Recreation Area has also been working since 2003 to restore areas along lower Redwood Creek.
The Tennessee Valley and Rodeo Lagoon watersheds are located within the Marin Headlands, part of GGNRA. Fort Cronkhite, an old Army mobilization post, is adjacent to Rodeo Lagoon and is also part of GGNRA. In the early 1990s, a draft watershed management plan for Tennessee Valley was completed by Golden Gate National Recreation Area. A 1998 study, The Landscape History of Tennessee Valley, describes the land use history of the watershed, ecological impacts of those land uses, and implications for park planning in the watershed.
1 Salmonid Trends in Redwood and Lagunitas Creeks
2 California Water Boards strategic Plan Updates 2008-2012