Lagunitas Creek
The Lagunitas Creek subwatershed is the largest drainage into Tomales Bay. The 24 miles long creek originates on the steep, forested slopes of Mount Tamalpais and drains an area of 103 square miles. Most of its major tributaries are dammed by Kent, Alpine, Bon Tempe, Lagunitas, and Nicasio reservoirs. The San Geronimo Valley is the last un-dammed headwater tributary of Lagunitas Creek and is considered critical Coho salmon spawning and juvenile rearing habitat.
The best part about the Lagunitas Creek subwatershed is that so much of the pristine upper watershed is on public lands. Marin Municipal Water District maintains an expansive trail system to explore the entire upper watershed on the north slope of Mt Tam, plus four (Gary Giacomini, White Hill, Roy’s Redwoods, French Ranch) Marin County Open Space Preserves, and just downstream is Samual P. Taylor State Park!
Lagunitas Creek’s major tributaries include San Geronimo Creek, Devils Gulch, Nicasio Creek, and Olema Creek. The creek’s source is the northern slope of Mount Tamalpais, a few miles east of Bolinas Lagoon. The creek begins as three forks, the East Fork, Middle Fork, and West Fork. After about a mile, they all flow into Lake Lagunitas, which drains into Bon Tempe Lake, which drains into Alpine Lake. At Alpine Lake the creek is joined by Liberty Gulch, Swede George Creek, and Cataract Creek which forms the spectacular Cataract Falls just before entering the lake. Downstream of Alpine Lake, the creek flows roughly northwest until it reaches Kent Lake. At Kent Lake it is joined by Kent Creek and Big Carson Creek. Just downstream of Kent Lake after flowing past the Leo T Cronin Fish Viewing Area and crossing under Sir Francis Drake Blvd., it reaches the confluence with San Geronimo Creek, right before it forms the Inkwells.
San Geronimo Creek itself captures the entire 9.4 square miles of San Geronimo Valley, starting at White Hill Preserve just west of Fairfax. As San Geronimo Creek flows down the valley through the communities of Woodacre, San Geronimo, Forest Knolls, and Lagunitas, it’s joined by tributaries from both sides of the valley, the larger including Creamery Creek, Clear Creek, and Arroyo Creek.
Lagunitas continues northwest along Sir Francis Drake Blvd. through Samuel P. Taylor State Park where it is joined by Irving Creek from the south, and Barnabe Creek, Devil’s Gulch, and Cheda Creek from the north. At Tocaloma the creek veers north alongside Platform Bridge Road. Just below Platform Bridge at the intersection with Pt. Reyes – Petaluma Road it is joined by Nicasio Creek, which flows from Seeger Dam, forming Nicasio Reservoir.
Nicasio Creek is an 11.9-mile-long stream with a watershed that drains 36 square miles of coastal area of Marin County and is the primary tributary of Lagunitas Creek. Originating on Big Rock Ridge west of the city of Novato, Nicasio Creek descends initially to the south. Approaching Lucas Valley Road, it turns and follows the road as it winds westward, passing south of Skywalker Ranch and through a redwood grove as it makes its way down to the community of Nicasio. North of Nicasio, it feeds into Nicasio Reservoir just as Halleck Creek enters from the east. The reservoir drains to the west, through a gap in the black basalt forming Bolinas Ridge. Seeger Dam is located approximately a mile upstream from the confluence of Nicasio and Lagunitas Creeks. The dam was constructed in 1960 by the Marin Municipal Water District (MMWD) to store water for cities in southern Marin County. From the dam, Nicasio Creek parallels Point Reyes-Petaluma Road westward until it empties into Lagunitas Creek.
Shortly after this confluence, Lagunitas turns westward and flows through the town of Point Reyes Station. On the west side of the town, the creek is joined by Olema Creek, the second largest tributary in the Lagunitas Creek watershed with a catchment area of 14.5 square miles. The mainstem of Olema Creek flows north for 9 miles along the San Andreas Fault Zone flowing between Shoreline Hwy and the Olema Valley and then Rift Zone Trails. At Olema the creek flows under Bear Valley Road and around the Olema Campground where it widens out and encompasses more marshland habitat before crossing under the bridge on Sir Francis Drake Blvd and merging with Lagunitas Creek. Just after Olema Creek, Bear Valley Creek also joins from the south at Whitehouse Pool County Park. Bear Valley Creek originates in Bear Valley within Point Reyes National Seashore before crossing Bear Valley Road and forming Olema Marsh. At the west end of Whitehouse Pool County Park Lagunitas Creek turns northward at its confluence with Haggerty Gulch Creek and then empties into the wetlands at the southeast end of Tomales Bay.
Dense mixed redwood forest along the creeks in the upper watershed keeps the water cool year-round. These shady creeks provide spawning and rearing habitat for salmonids. Most of Lagunitas Creek downstream of the Samuel P. Taylor State Park is thickly forested with willows and alders. Below Tocaloma Bridge, the Lagunitas watershed opens into a valley with broad, gently sloping hills. This area is primarily used for livestock grazing.
A significant population of wild Coho salmon still exist in the Lagunitas watershed and Pacific lamprey spawn in Lagunitas Creek. Until the early 1980s, green sturgeon used the lower reaches. Mountain lions are frequently seen in the watershed and river otters have been sighted in the mainstem of Lagunitas. An osprey colony has been active at Kent Lake since the 1960s and bald eagles have been sighted in recent years.
Other listed species currently observed in the watershed include Northern spotted owl, Steelhead trout, California freshwater shrimp, Foothill yellow-legged frogs, California-red legged frog, and Chinook salmon.
Tomales Bay East Shore
The small tributaries draining the east side of Tomales Bay include Tomasini Canyon Creek, Grand Canyon Creek, Millerton Gulch Creek, Ranch House Creek, Nick’s Cove Creek, Pipefish Creek and other unnamed tributaries. Other than Millerton Point and Marconi State Parks and Marin County’s Miller Boat Launch, most of these small watersheds occur on private lands.
Tomales Bay’s east shore is mostly grassland with oak-bay woodlands, coastal scrub, and eucalyptus. Fresh and saltwater marshes line Tomales Bay’s east shore and scattered stands of coastal terrace prairie exist along the east shore’s tributaries.
Walker Creek
The mainstem of the 18.5 miles long Walker Creek is formed by the confluence of Sausal Arroyo and Salmon Creek just below the Soulajule Reservoir along Marshal-Petaluma Rd. Topography in the 76-square mile Walker Creek watershed ranges from 1,500 feet to sea level where the creek empties into Tomales Bay just south of its mouth with Bodega Bay. The upper watershed is much more rugged with extensive areas of coast live oak forest. Other than Soulajule Reservoir, the rest of the land in the Walker Creek subwatershed is privately owned.
Arroyo Sausal headwaters begin on the ridgeline just west of Stafford Lake and flow northwest, crossing Point Reyes-Petaluma Road into Hicks Valley at the Cheese Factory, then west to Soulajule Reservoir where it is joined by Three Peaks Creek. The headwaters of Salmon Creek flow west 4.5 miles along Hicks Valley Road then Marshall-Petaluma Road to meet Arroyo Sausal below the reservoir forming Walker Creek. Salmon Creek was described historically as a salmon and steelhead trout spawning and nursery area, although it has been seriously damaged by poor farming practices, dairy pollution, and soil erosion.
From the confluence of Arroyo Sausal and Salmon Creek, Walker Creek descends to the northwest, paralleling Marshall-Petaluma Road as it curves westward. At the confluence with Verde Canyon Creek, Walker Creek crosses under the road and turns northwest, passing through Walker Creek Ranch where it’s joined by Frink Canyon Creek, before continuing to the confluence with Chileno Creek. Chileno Creek flows 6.25 miles west along Bolinas Ridge to Walker Creek and originates from Laguna Lake, a 220-acre natural lake which straddles the Marin County – Sonoma County border at the top of Chileno Valley.
From the Chileno Creek confluence, Walker Creek meanders westward, passing south of the community of Tomales. It crosses under Highway 1 and is immediately joined by Keys Creek, entering from the north and Quarry Creek from the northwest. The 3.5 miles long Keys Creek gathers and flows along Tomales – Petaluma Road and from the surrounding area of the community of Tomales. The northern tributaries, Chileno Creek, Keyes Creek and Quarry Creek, flow through wide valleys with gentle, grassy hills. Below Keys and Quarry Creeks, Walker Creek continues southward along the Highway 1 to enter Tomales Bay just east of Preston Point.
Walker Creek contains a mosaic of different habitats including annual grassland, perennial grassland (near the coast), valley foothill riparian forest, limited redwood forest, coastal scrub, and oak bay woodlands. Due to its shallow depth, Laguna Lake is classified as a vernal pool that retains water year-round, though significantly less water in summer. The lake is used extensively by migrating and breeding waterfowl and amphibians. Wetlands at the mouth of Walker Creek also provide important habitat for waterfowl. The grasslands of Walker Creek are an excellent place to find raptors including Swainson’s hawks, Ferruginous hawks, and Golden eagles. Restored riparian corridors in Chileno Valley attract a variety of neotropical songbirds species including Warblers, Vireos, and Flycatchers.
Remember, storm drains connect streets to creeks. Simple changes can make a big impact. Tomales Bay Watershed is Ours to Protect.
