Bolinas Lagoon land use and habitat

Bolinas Lagoon represents a unique habitat within the watershed, consisting of:

• Mudflats
• Marshes
• Tidal channels
• Flood shoal island

The primary vegetation communities within the watershed are:

• Coastal scrub
• Douglas fir and redwood forest
• Grasslands

There are small patches of:

• Eucalyptus
• Oak and oak-bay woodlands
• Riparian scrub woodland
• Pine cypress forest

Easkoot Creek is located within one of the most biologically diverse and ecologically significant areas on the California coast. .Easkoot Creek drains an area of approximately 1.59 square miles. The area is mostly undeveloped and steeply forested watershed on the side of Mt. Tam.  The watershed supports a mix of upland and aquatic habitats.  It borders:

• State and federal parks
• Private property
• Local municipality lands.

Upland habitats

Upland habitats are dominated by coast redwood and Douglas fir forest along the inner gorges, chaparral on the convex slopes, and grasslands with a strong native component. However, the riparian plant community along Easkoot Creek contains the largest number of non-native plants when compared with other east-side tributaries.  Only isolated remnants of historic willow and alder forest remain.

The Easkoot Creek watershed is within the Pacific Flyway, “the major corridor for movement of migratory shorebirds, raptors, and other birds along the West Coast of North America.”

Saltmarsh habitat

A complex of habitats supports a variety of species at the mouth of Easkoot Creek at Bolinas.  The finger of lagoon that extends to the mouth of Easkoot Creek, commonly referred to as south arm, supports saltmarsh habitat, frequently exposed mudflats, and subtidal channels, all bordered by development on the Stinson Beach Spit.

In recent years, saltmarsh habitat has been expanding in the south arm due to the restoration of a more natural tidal range following the removal of the constriction caused by the Stinson Gulch delta.

This area serves as a nursery for fish, harbor seals haul out on the mudflats. Rails are present. An abundance of invertebrates provide a food source for shore and waterbirds (PWA 2006).

Easkoot Creek drains into the east side of Bolinas Lagoon and is the second largest drainage in the watershed.  Several small tributaries (Fitzhenry, Laurel, and Black Rock Creeks) drain the upper watershed.  Much of the upper watershed is publicly owned and supports a mix of forested, chaparral, and grassland habitats.  The lower watershed is mostly privately owned and more heavily developed.  It is tidally influenced with saltmarsh forming the transition zone between mainstem Easkoot Creek and Bolinas Lagoon.

The watershed supports a number of special-status plants and animals.  Of particular interest are the occurrences of species found in coastal marsh and scrub along the Bolinas Lagoon Spit and in the vicinity of Stinson Beach.

Noteworthy species in Bolinas Lagoon include:

• Ridgway's and black rails, salt marsh common yellowthroat, great egrets, and great blue herons occur around the lagoon
• California red-legged frog are known to occur adjacent to the lagoon in freshwater ponds

The 1996 Bolinas Lagoon Management Plan Update identifies additional special-status species found in the Bolinas Lagoon watershed, including:

• California brown pelican
• American peregrine falcon
• Point Reyes mountain beaver
• Point Reyes jumping mouse

In Pine Gulch Creek, species include:

• Coho salmon
• Steelhead trout
• Northern spotted owl
• Salt marsh common yellowthroat
• Black swift
• California red-legged frog
• Marin manzanita

Since 1997, the National Park Service Coho Salmon and Steelhead Trout Restoration Program staff has been actively monitoring fish populations along 12 kilometers of mainstem Pine Gulch Creek. Coho salmon were documented within the watershed in 1968, but monitoring by NPS staff failed to document a single Coho salmon from the fall of 1997 to the summer of 2000.  Since that time, Coho salmon have been documented annually by NPS staff in Pine Gulch Creek.

Since 2001, the highest number of adult spawners were observed during the 2004-2005 year class in which three adults and three redds (where female salmon deposit eggs) were observed.  In 2007-2008, one Coho salmon and two redds were observed (NPS 2008 7).

California red-legged frog and steelhead trout are known to occur in Wilkins Gulch.

Steelhead trout are known to occur in:

• Morse’s Gulch
• McKinnon Gulch
• Stinson Gulch

The Easkoot Creek subwatershed is known to support a remnant population of steelhead. According to Fong (2002), the historic distribution of steelhead within the watershed is roughly similar to their distribution today. However, the current population size does not reflect historic abundance.

The subwatershed may support California red-legged frog, federally listed as threatened and Species of Special Concern; however, there are no documented occurrences. Red-legged frogs have been documented in a small brackish pond on the east side of Shoreline Highway in the north end of the lagoon.

Much of the watershed is in public ownership. Private communities occur within the Pine Gulch Creek subwatershed. Some private parcels within Pine Gulch Creek are used for farming. Much of the Easkoot subwatershed is county, state, and federal parkland.

The Golden Gate National Recreation Area was formed in 1972. It acquired most of the open land surrounding the community of Stinson Beach.  Other protected lands include:

• Bolinas Lagoon
• Mt. Tamalpais State Park

Organic farmers along Pine Gulch Creek have established a cooperative agreement with local agencies to protect water in creeks for Coho salmon and steelhead trout habitat, while also maintaining local agriculture. For more information, visit the Marin Resource Conservation District website.

Changes to the watershed

There are early maps from the 1900s of the proposed subdivision development. They show the creek channel close to its present alignment until just downstream of the sharp turn at Arenal Avenue. The historic channel then branches off as the channel slope loses its grade and enters a willow thicket (on the current Park Service land).

Early maps show an alternative alignment for Easkoot Creek breaching the sand dunes. With the development of Stinson Beach and the public park, Easkoot Creek has been maintained in its current alignment to Bolinas Lagoon.

Historic land use activities that could and may still be contributing to the sedimentation problem in the lagoon are addressed in the Historical Perspective of Bolinas Lagoon Watershed.

The Bolinas Lagoon Watershed Study: Input Sediment Budget evaluates “the sources and magnitude of sediment delivered to the lagoon via erosional processes within the watershed.”  This study concluded that current erosion rates are near background (pre-1850) levels within the watershed.

Residential and commercial use

The watershed supports limited residential and commercial use. Commercial uses are generally geared toward serving the large summer tourist population. Stinson Beach residential use is at its peak in the summer, when single-family homes may be occupied by multiple families coming to the area for vacations. While the community of Stinson Beach remains small (fewer than 1,000 residents) and seasonal occupancy remains a typical community feature, full-time residential use is increasing (Stetson 2006 8).

Easkoot Creek

Easkoot Creek originates in the steep, west-facing slopes of Bolinas Ridge.  Three tributaries join to form Easkoot Creek just upstream of Shoreline Highway in Stinson Beach:

• Fitzhenry Creek
• Laurel Creek
• Black Rock Creek

After exiting the uplands, the Creek turns northwest and flows behind the coastal dune until it enters the south arm of Bolinas Lagoon.  It has been debated whether or not the creek historically flowed to the Lagoon or went straight out to the ocean.  Recent research indicates that the current channel location very closely matches its historic location near Arenal, and that only during high flow events would the creek change its course and flow directly to the ocean across the beach.

The steep slopes of the upper Easkoot watershed are prone to landslides.  Sediment derived from the hillslopes is transported to the low gradient and tidally influenced reaches where it is stored in the channel.  In order to maintain channel capacity, the County and National Park Service has had to remove sediment from the creek near the Park Service parking lots.

Nearly 170 meters of Easkoot Creek through the town of Stinson Beach has riprap, SacCrete, gabions, or retaining walls stabilizing its banks. Over the years levees had been built up along lower Easkoot Creek, adjacent to the National Park Service lands, with spoils from sediment dredging activities. These artificial levees restricted hydrologic connectivity of the stream to its floodplains and adjacent wetlands.  Portions of the creek extending to Bolinas Lagoon were likely created as homes were built as historical maps show the creek disappearing into willows without a outlet to the lagoon.

The lower reach of Easkoot Creek flows through a tidal marsh located between Shoreline Hwy and Calle del Arroyo.  With the start of construction of the Seadrift lagoon and subdivision in 1960, and the presence of the delta at the mouth of Stinson Gulch, tidal circulation to the southeastern arm of Bolinas Lagoon was restricted.  Removal of the Stinson Gulch delta constriction and the restoration of a more natural tidal range allowed the marsh at the mouth of Easkoot Creek to nearly double in size between 1968 and 1998.

Flooding

There are three sources of flooding in Stinson Beach:

• Overflow of Easkoot Creek
• Extremely high tides
• Extremely high surf

Each of these alone can cause some flooding. When combined, they can cause substantial flooding, property damage, and public safety problems. The Arroyo and Calle area of Stinson beach are flooded each year during extreme high tide events.

Dredging

Periodic dredging was one of the primary maintenance tasks when Flood Control Zone 5 was first established. Over time it has become evident that during medium to large storm events an active slide on Mt. Tam releases enough hillside material to fill in the creek, even if it was recently dredged.

The essentially flat reach from Arenal to Bolinas Lagoon creates a slower moving creek and a natural area for sediment to settle and deposit. The excessive sediment build-up within this reach of Easkoot Creek has significantly reduced the level of flood protection through the Calle area of Stinson Beach.

Calle bridges

The private bridges along the residential streets known collectively as the “Calles” have limited to no clearance from the creek during storms. This may contribute to the flooding of neighboring homes and prevent access to and from Shoreline Highway. These bridges are a hydraulic constraint, but they are the primary access to homes and the primary access for emergency vehicles.

The County and Flood Control Zone 5 has spent significant funds to perform limited dredging at the Calle bridges. It is usually only effective for one to two seasons. It requires dewatering the channel and relocating Steelhead trout to minimize impacts.

Sediment removal permit

As a condition of the sediment removal permit, regulatory agencies required that we investigate alternatives to the dewatering and the spot dredging approach since the creek has an established run of Steelhead.

The result of this investigation was the construction and maintenance of a sediment trap. It is on Park Service property, downstream of Arenal Avenue. The trap allows for sediment removal at one location in the beach park instead of multiple locations downstream. It reduces impacts to Steelhead and other aquatic life.

Restoration and conservation

For over thirty years, local community groups and scientists have brought attention to the:

• Ecological value of the lagoon
• Need to slow sediment deposition to preserve it

Community groups and studies

The County Board of Supervisors appointed the Bolinas Technical Advisory Committee in 1974. The  Bolinas Lagoon Foundation established the Committee to Save Bolinas Lagoon in 1994.

The Committee to Save Bolinas Lagoon worked with local experts to secure funds from Congress. They used this for initial studies for restoring the lagoon.

The Marin County Open Space District developed a management plan in 1981 to address:

• Loss of tidal and subtidal habitat and
• Sedimentation in Bolinas Lagoon

The plan was revised in 1996. Marin County Open Space leads a project to improve the Bolinas Wye to allow room for the lagoon to expand with sea level rise. 

A working group of community representatives and scientists completed the Bolinas Lagoon Ecosystem Restoration Project: Recommendations for Restoration and Management in 2008. The Gulf of the Farallones National Marine Sanctuary Advisory Council coordinated the study, with support from: 

• Marin County Open Space District
• United States Army Corps of Engineers 

Recommendations

Restoration objectives and recommended actions include:

• Restoring natural sediment transport and ecological functions of the lagoon
• Identifying and managing non-native species
• Protecting water quality

Each of these restoration objectives are complemented by a set of management recommendations. They include:

• Implementing best management practices throughout the watershed
• Removing fallen trees from the lagoon
• Establishing a public education program to reduce human disturbance of harbor seals
• Immediately removing introduced cordgrass found in the Lagoon
• Developing emergency response plans to address the closure of the lagoon inlet or an oil spill